AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSGX 230 PM PST MON JAN 15 2007
.SYNOPSIS...SURFACE HIGH PRESSURE OVER UTAH WILL CAUSE LOCAL STRONG
GUSTY WINDS THROUGH TUESDAY...MAINLY THROUGH AND BELOW MOUNTAIN
CANYONS AND PASSES. WARMER DAYS THROUGH THURSDAY AND NOT QUITE AS
COLD AT NIGHT. UPPER LEVEL LOW PRESSURE WILL BRING MORE CLOUDS OVER
THE WEEKEND WITH A CHANCE OF SHOWERS.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM (TODAY-THU)...CLEAR SKIES TODAY. ACARS SOUNDINGS SHOWED
NE WINDS 15 TO 30 KT IN THE LOW LEVELS WITH NW WINDS ALOFT. OFFSHORE
GRADIENTS WITH ABOUT -8 MB SAN-TPH.
THERE WILL CONTINUE TO BE ENOUGH UPPER...THERMAL AND GRADIENT
SUPPORT FOR LOCAL STRONG GUSTY OFFSHORE WINDS THROUGH TUE. THE WINDS
SHOULD SHOW THE USUAL PATTERN OF DECREASING OVERNIGHT AND THEN
INCREASING AGAIN TUE MORNING BEFORE FINALLY DECREASING AGAIN TUE
AFTERNOON. THE STRONGEST WINDS WILL BE TODAY WITH NOT QUITE AS
STRONG WINDS TUE MORNING. THE CURRENT WIND WARNINGS AND ADVISORIES
LOOK GOOD. THE DRY OFFSHORE FLOW WILL INCREASE THE FIRE WEATHER
HAZARD AND A RED FLAG WARNING IS IN EFFECT FOR THE
MOUNTAINS...INLAND VALLEYS AND ORANGE COUNTY COASTAL AREAS UNTIL
6 PM TUE. A LITTLE WARMER IN MOST AREAS TUE AND WED...ESPECIALLY W
OF THE MOUNTAINS. MORE WARMING THU AS HEIGHTS INCREASE IN MILD SW
FLOW ALOFT. IT WILL ALSO BE MILDER AT NIGHT. HOWEVER...THERE WILL
STILL BE LOCAL FROST TONIGHT AT THE LOWER ELEVATIONS IN AREAS
PROTECTED FROM THE WINDS. IT WILL NOT BE QUITE AS COLD AS PREVIOUS
NIGHTS AND WINDS WILL CAUSE FLUCTUATING MIN TEMPS FOR SHORTER FROST
DURATIONS. THERE WILL BE INCREASING HIGH CLOUDS THU IN THE SW FLOW
ALOFT.
.LONG RANGE (FRIDAY-MONDAY)...PROGS INDICATE THE UPPER LOW OFF THE
COAST WILL SLOWLY MOVE E FRI FOR MORE MID TO HIGH CLOUDS AND A
LITTLE COOLING. THE LOW COULD TAP INTO TROPICAL MOISTURE WITH A JET
JUST S OF SAN DIEGO THIS WEEKEND FOR A CHANCE OF SHOWERS.
HOWEVER...BECAUSE THE LOW WILL BE CUT OFF FROM THE MAIN FLOW THE
TIMING AND PRECIP AMOUNTS A VERY UNCERTAIN. DRYER OFFSHORE FLOW
SHOULD DEVELOP EARLY NEXT WEEK.
&&
.AVIATION...
GUSTY OFFSHORE WINDS WILL CONTINUE OVERNIGHT INTO TUESDAY NEAR AND
BELOW PASSES AND CANYONS...THEN WEAKEN LATE TUESDAY AFTERNOON INTO
WEDNESDAY. THE STRONGEST WINDS ARE EXPECTED BELOW THE CAJON PASS IN
THE INLAND EMPIRE AND NEAR THE SANTA ANA MOUNTAINS. THESE WINDS WILL
GENERATE AREAS OF TURBULENCE...STRONG UP AND DOWN DRAFTS...AND
MOUNTAIN WAVES WITH ROTORS. THERE WILL LIKELY BE AREAS OF BLOWING
DUST AS WELL. OTHERWISE VFR CONDITIONS WILL PREVAIL WITH CLEAR SKIES
AND GENERALLY UNRESTRICTED VSBYS.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 3 PM TUESDAY FOR...THE INLAND EMPIRE...SAN
BERNARDINO MOUNTAINS AND SANTA ANA MOUNTAINS. SEE LAXNPWSGX.
WIND ADVISORY UNTIL 3 PM TUESDAY FOR...ORANGE COUNTY COASTAL
AREAS...SAN DIEGO COUNTY VALLEYS...RIVERSIDE COUNTY MOUNTAINS AND
SAN DIEGO COUNTY MOUNTAINS. SEE LAXNPWSGX.
RED FLAG WARNING UNTIL 6 PM TUESDAY FOR ALL MOUNTAINS AND INLAND
VALLEY AREAS AND FOR THE ORANGE COUNTY COASTAL AREAS. SEE LAXRFWSGX.
$$
PUBLIC...DVA
AVIATION...SCV
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSGX 930 AM PST MON JAN 15 2007
.SYNOPSIS...SURFACE HIGH PRESSURE OVER UTAH WILL CAUSE LOCAL STRONG
GUSTY WINDS THROUGH TUESDAY...MAINLY THROUGH AND BELOW MOUNTAIN
CANYONS AND PASSES. WARMER DAYS THROUGH THURSDAY AND NOT QUITE AS
COLD AT NIGHT. UPPER LEVEL LOW PRESSURE WILL BRING MORE CLOUDS OVER
THE WEEKEND WITH A CHANCE OF SHOWERS.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM (TODAY-THU)...CLEAR SKIES TODAY. ACARS SOUNDINGS SHOWED
NE WINDS TO 20 KT IN THE LOW LEVELS WITH WLY WINDS ALOFT. OFFSHORE
GRADIENTS WITH ABOUT -10 MB SAN-TPH.
THERE WILL CONTINUE TO BE ENOUGH UPPER...THERMAL AND GRADIENT
SUPPORT FOR LOCAL STRONG GUSTY OFFSHORE WINDS THROUGH TUE. THE WINDS
SHOULD SHOW THE USUAL PATTERN OF DECREASING OVERNIGHT AND THEN
INCREASING AGAIN TUE MORNING BEFORE FINALLY DECREASING AGAIN TUE
AFTERNOON. THE STRONGEST WINDS WILL BE TODAY WITH NOT QUITE AS
STRONG WINDS TUE MORNING. THE CURRENT WIND WARNINGS AND ADVISORIES
LOOK GOOD. THE DRY OFFSHORE FLOW WILL INCREASE THE FIRE WEATHER
HAZARD AND A RED FLAG WARNING IS IN EFFECT FOR THE
MOUNTAINS...INLAND VALLEYS AND ORANGE COUNTY COASTAL AREAS UNTIL
6 PM TUE. A LITTLE WARMER IN MOST AREAS TUE AND WED...ESPECIALLY W
OF THE MOUNTAINS. MORE WARMING THU AS HEIGHTS INCREASE IN MILD SW
FLOW ALOFT. IT WILL ALSO BE MILDER AT NIGHT. HOWEVER...THERE WILL
STILL BE LOCAL FROST TONIGHT AT THE LOWER ELEVATIONS IN AREAS
PROTECTED FROM THE WINDS. IT WILL NOT BE QUITE AS COLD AS PREVIOUS
NIGHTS AND WINDS WILL CAUSE FLUCTUATING MIN TEMPS FOR SHORTER FROST
DURATIONS. THERE WILL BE INCREASING HIGH CLOUDS THU IN THE SW FLOW
ALOFT.
.LONG RANGE (FRIDAY-MONDAY)...PROGS INDICATE THE UPPER LOW OFF THE
COAST WILL SLOWLY MOVE E FRI FOR MORE MID TO HIGH CLOUDS AND A
LITTLE COOLING. THE LOW COULD TAP INTO TROPICAL MOISTURE WITH A JET
JUST S OF SAN DIEGO THIS WEEKEND FOR A CHANCE OF SHOWERS.
HOWEVER...BECAUSE THE LOW WILL BE CUT OFF FROM THE MAIN FLOW THE
TIMING AND PRECIP AMOUNTS A VERY UNCERTAIN. DRYER OFFSHORE FLOW
SHOULD DEVELOP EARLY NEXT WEEK.
&&
.AVIATION...
GUSTY OFFSHORE WINDS WILL CONTINUE TODAY AND TONIGHT NEAR AND BELOW
PASSES AND CANYONS. THE STRONGEST WINDS ARE EXPECTED BELOW THE CAJON
PASS IN THE INLAND EMPIRE AND NEAR THE SANTA ANA MOUNTAINS. THESE
WINDS WILL GENERATE AREAS OF TURBULENCE...STRONG UP AND DOWN
DRAFTS...AND MOUNTAIN WAVES WITH ROTORS. THERE WILL LIKELY BE AREAS
OF BLOWING DUST AS WELL. OTHERWISE VFR CONDITIONS WILL PREVAIL WITH
CLEAR SKIES AND GENERALLY UNRESTRICTED VSBYS.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 3 PM TUESDAY FOR...THE INLAND EMPIRE...SAN
BERNARDINO MOUNTAINS...SANTA ANA MOUNTAINS. SEE LAXNPWSGX.
WIND ADVISORY UNTIL 3 PM TUESDAY FOR...ORANGE COUNTY COAST...SAN
DIEGO COUNTY VALLEYS...RIVERSIDE COUNTY MOUNTAINS...AND SAN DIEGO
COUNTY MOUNTAINS. SEE LAXNPWSGX.
RED FLAG WARNING UNTIL 6 PM TUESDAY FOR...THE INLAND EMPIRE...SAN
DIEGO COUNTY VALLEYS...ALL MOUNTAINS. SEE LAXRFWSGX.
$$
PUBLIC...DVA
AVIATION...SCV
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
AFDLOT 510 PM CST TUE JAN 16 2007
.DISCUSSION FOR AFTERNOON GRIDS/ZONES...
310 PM CST
LAKE EFFECT SNOW TRENDS MAIN SHORT TERM FOCUS FOR FIRST FEW HOURS
TONIGHT.
WEAK VORT/POS TILT UPPER TROF AXIS MOVG EAST OF FCST AREA THIS AFTN.
WEAKENING SFC PRES GRADIENT AS SFC HIGH APPRCHG FROM WEST...WITH
MODEL TSECTS DEPICTING STRONG AND DEEP SUBSIDENCE DVLPG ATTM. RECENT
ACARS SOUNDINGS OUT OF KORD SHOW DIRECTIONAL SHEAR INCREASING THRU
ABOUT 750 HPA ALONG WITH DECREASING WIND SPEEDS...AND THIS LACK OF
ORGANIZATION RESULTING IN DVLPMNT OF ONE TIME SINGLE BAND LES EVENT
NOW TAKING ON MORE OF A THERMALLY FORCED MESO LOW STRUCTURE AS IT
FADES. RADAR AND VIS SATELLITE IMGRY FROM LAST HOUR OR SO VERY
IMPRESSIVE WITH THIS TRANSITION...LOOKING LIKE A MINI SNOW HURRICANE
COMPLETE WITH AN EYE AT 1951Z. IT BEGS TO BE NAMED. WILL HAVE TO
CONTEND WITH SNOW SHOWERS ACROSS NORTHERN LAKE/PORTER COUNTIES FOR
REMAINDER OF AFTN HOURS AS THIS LES BAND CONTINUES TO DECAY...THOUGH
ANTICIPATE THAT COMBINATION OF VERY DRY LOW LVLS...STRENGTHENING AND
LOWERING SUBSIDENCE INVERSION AND LOSS OF LLVL CONVERGENCE WILL
ALLOW PCPN TO COME TO AN END BY EARLY EVENING.
WITH SFC RIDGE BUILDING ACROSS FCST AREA TNGT...AND SNOW COVER IN
PLACE MOST AREAS...SET UP FOR STRONG RADIATIONAL COOLING. LLVL
PARCEL TRAJECTORIES FROM NERN IA...WHERE TEMPS DIPPED BLO ZERO THIS
MRNG. WILL CONTINUE TO UNDERCUT ALL GUIDANCE NUMBERS FOR MINS
OVRNGT...WITH CURRENT GRIDS ACTUALLY LOOKING QUITE GOOD RANGING FROM
AROUND -3 NW WHERE DEEPEST SNOW COVER EXISTS...TO NEAR 10 ABOVE
SOUTHEAST WHERE SNOW COVER MINIMAL.
MID LVL S/WV RDG MOVS ACROSS FCST AREA WED MORNING...WITH TSECTS AND
FCST SOUNDINGS CONTINUING TO DEPICT VERY DRY AMS. SHOULD SEE PLENTY
OF SUNSHINE...WITH A LITTLE REBOUND IN TEMPS AS WAA DVLPS IN SWLY
FLOW ON BACK SIDE OF SFC RIDGE DURG AFTN. S/WV TROF THEN MOVG OUT OF
HIGH PLAINS WED NGT EXPCTD TO GENERATE SOME MID CLOUD COVER AFTER
MIDNIGHT AS IT APPROACHES UPPER MS VLY TOWARD MRNG. SWLY LLVL FLOW
10-15 MPH SHOULD HELP TEMPS KEEP FROM DROPPING TOO FAR WED
EVENING...THOUGH HAVE STILL GONE A BIT BLO COLDEST FWC NUMBERS.
S/WV MOVES ACROSS FCST AREA THURSDAY...WITH MODELS IN AGREEMENT IN
DROPPING SECOND WAVE IN BY LATE IN THE DAY. TSECTS INDICATE LOW
LEVELS MOISTEN DURG THE AFTN HOURS AS LLVL COLD ADVECTION STARTS TO
KICK IN...THOUGH MOISTURE FAIRLY SHALLOW AND LIFT FOCUSED MORE IN
MID LEVELS. WRF/GFS DO ATTEMPT TO KICK OUT SOME VERY LIGHT QPF
MAINLY NORTH OF THE FA HOWEVER...SO WILL MAINTAIN CHC OF FLURRIES
DURG MAX LLVL CAA/SATURATION THURSDAY NIGHT.
FOR REMAINDER OF FCST...INCREASING SPREAD IN ENSEMBLE SOLUTIONS WITH
PATTERN HEADING INTO NEXT WEEKEND. OVERALL TREND SUPPORTS MORE OF A
TROUGHINESS ACROSS THE AREA...WITH PERHAPS BEST FOCUS FOR ORGANIZED
PCPN ARRIVING SUN/SUN NGT. HPC FAVORING ECMWF/GEM HANDLING OF LATER
PERIODS AND WILL NOT ARGUE AT THIS POINT. THUS WILL HAVE CHC LGT
SNOW SUN/SUN NGT...THEN CHC SNOW SHOWERS/FLURRIES MONDAY/MON NGT.
TEMPS REMAIN RELATIVELY COLD THRU PERIOD...ESPECIALLY IN WAKE OF
COLD FRONT THURSDAY NIGHT/FRIDAY...AND WITH PASSAGE OF NEXT SFC HIGH
PRES RIDGE FRI NGT/EARLY SAT.
RATZER
&&
.AVIATION...
510 PM CST
RE 00Z TAFORS...MESO LO FORMED OVR SRN LK MI AS PRES GRADIENT
WEAKENED AS SFC RDG MOVD OVR THE UPPER MS VALLEY. CIRCULATION HAS
MOVD ASHORE AT 22Z AND LK EFFECT -SHSN BTWN GARY AND MI CITY WILL
CONT TO DIMINISH THIS EVE. RDG MOVG OVR TERMINALS THIS EVE WITH SNOW
COVER PROMOTING RAPID DECOUPLING OF BL AND WNDS GO LGT AND BACK
OVRNITE AS RDG AXIS DROPS ACROSS CNTRL IL AND IND. PRES GRADEINT
INCREASES AHEAD OF SFC TROF MOVG E ACROSS THE NRN PLAINS WED AND SW
WINDS WILL PICK UP MID TO LATE MORNING AFTER SFC BASED INVERSION
GETS MIXED OUT BUT TIGHTER GRADIENT AND STRONGER WINDS REMAIN TO W
AND N OF TERMINALS THU WED AFTERNOON. BESIDES REMNANTS OF LK EFFECT
STRATOCU VC GYY THIS EVE...SKC EXPECTED TO PREVAIL DUE TO STRONG
SUBSIDENCE TONIGHT WITH RIDGING SFC AND ALOFT AND LACK OF MOISTURE
WHEN WAA SETS IN AHEAD OF UPR TROF DURG WED.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LM...SMALL CRAFT ADVISORY THROUGH TUESDAY NIGHT.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
AFDLOT 425 AM CST MON JAN 15 2007
.DISCUSSION REGARDING 400 AM CST FORECAST ISSUANCE...
HAVE CANCELLED ALL WINTER WX HEADLINES.
RADAR AND SATLT LOOPS INDICATE THAT DRY SLOT...ASSD WITH SHEARING
VORT MAX NOW OVR NERN IA/SWRN WI INVOF LSE...HAS PUNCHED THRU MOST
OF FA. THE NAM INITIALIZED BEST AGAIN PAST TWO MDL RUNS AND
CONTINUES TO BE THE MODEL OF CHOICE. THIS GUIDANCE PIVOTS AXIS OF
HANG BACK PCPN NOW ORIENTED SW-NE FROM IA-NRN WI...EWD ACROSS UPR
MIDWEST THRU TDY. SATLT EXTRAPOLATION OF SRN END OF THIS ENHANCED
AREA SUPPORTS NAM...AND EXPECT THAT PERIODS OF LGT SNOW WILL CONT
ACRS EXTRM NRN IL AHD OF MAIN H5 TROF AXIS MOST OF TDY...WITH ADDL
ACCUMULATIONS LESS THAN 1 IN. TEMPS WILL LIKELY HOVER ABOUT WHERE
THEY ARE NOW...AND THEN BEGIN A SLOW FALL BY LATE MRNG AS SFC PRES
BEGINS TO RISE FURTHER UPSTREAM IN POLAR AMS. THIS WILL INCR COLD
ADVECTION THIS AFTN AND TNGT. WILL KEEP MENTION OF FLRYS IN ALL
AREAS INTO TUES MRNG DUE TO LLVL CAA AND WITH APCH OF MID LVL TROF
AXIS. NO SIG PCPN THIS AFTN OR TNGT XCP IN PORTER CO WHERE LAKE
EFFECT SNOW SHWRS MAY RESULT IN SOME MINOR ACCUMULATIONS TNGT.
CURRENT FCST PARCEL TRAJECTORIES SUGGEST BETTER CHC FOR SIG LAKE
EFFECT EVENT WILL BE JUST TO E OF FA.
LTL CHG MADE TO RMNDR OF FCST WITH A COUPLE OF REINFORCING COLD
SHOTS FCST WITH PASSAGE OF CLIPPER TYPE SYS...THE MOST SIG OF WHICH
IS FCST THRU UPR MIDWEST ON THUR. CURRENTLY FCST PATH OF VORT MAX
IS INTO NRN IL BY THUR EVENING SO EXPECT ANY MEAS SNOW WITH THIS
FEATURE TO BE TO OUR N AND FURTHER INTO COLDER AIR.
MERZLOCK
&&
.AVIATION...
FOR 12Z TAFS...MID LEVEL DRYING FROM ABOUT 700-500MB SEEN IN MODEL
SOUNDINGS EVIDENT IN RADAR LOOPS AS BULK OF PRECIP HAS EXITED AREA.
ALL THAT REMAINS ARE SMALL WEAK BANDS OF LAKE EFFECT SNOW SEEN IN
RADAR LOOP MOVING SW FROM THE LAKE INTO THE CHICAGO AREA.
VISIBILITIES DOWN TO ABOUT 2 MILES IN SNOW AT TIMES. NNE WINDS
SHOULD TURN N BY MID MORNING...THEN NNW BY EARLY AFTERNOON...BRINING
AN END TO THE LAKE EFFECT...EXCEPT IN GARY WHERE IT COULD LAST INTO
EVENING. ACARS AND MODEL SOUNDINGS INDICATE ENTIRE LAYER...EXCEPT
FOR SURFACE...NOW BELOW FREEZING...SO PRECIP SHOULD BE MAINLY SNOW.
BUT WITH DRYING OCCURRING IN BEST ICE CRYSTAL GROWTH REGION...SOME
FREEZING DRIZZLE STILL POSSIBLE THIS MORNING. BY AFTERNOON EVEN
LOWER PART OF SOUNDING...DOWN TO 800 MB OR SO...DROPS TO ABOUT -10
SO ONLY SNOW EXPECTED THIS AFTERNOON AND TONIGHT. SOME HANGBACK
MOISTURE ACROSS WISCONSIN AND IOWA IS FORECAST BY MODELS TO MOVE
ENE. SOME VERY LIGHT SNOW SHOWERS OR FLURRIES POSSIBLE THROUGH THE
DAY AND INTO TONIGHT BUT BEST SHOT SEEMS TO BE TOWARD THE WISCONSIN
BORDER AND ESPECIALLY LATE AFTERNOON AND EVENING. SHOULD NOT BE
SIGNIFICANT WITH ONLY BRIEF MVFR VISIBILITIES.
IFR CIGS SHOULD IMPROVE AFTER DAYBREAK AND SHOULD LIFT ABOVE 2000
FEET BY THIS EVENING. EXPECT CLEARING TUESDAY MORNING...BUT BEYOND
SCOPE OF THIS FORECAST.
NNE WINDS THIS MORNING SHOULD TURN N BY MID MORNING AND NNW BY EARLY
AFTERNOON. EXPECT WINDS TO PICK UP AND GUST TO AROUND 20 TO 25 KNOTS
IN THE AFTERNOON. GUSTINESS SHOULD SUBSIDE AFTER DARK BUT WINDS WILL
STAY BRISK THROUGH TUESDAY.
ALLSOPP
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...NONE
.IN...NONE
.LM...SMALL CRAFT ADVISORY THROUGH TUESDAY NIGHT.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
AFDIWX 1245 AM EST MON JAN 15 2007
.AVIATION...
WIDESPREAD RAIN AND FREEZING RAIN ACROSS THE AREA TONIGHT. KFWA
HOVERING JUST ABOVE FREEZING AND KSBN RIGHT AT FREEZING. PREDOMINATE
FREEZING RAIN EXPECTED AT KSBN REST OF NIGHT WHILE FORT WAYNE LIKELY
TO BE MAINLY RAIN BUT FREEZING AT TIMES WITH TEMPERATURE WAVERING
BETWEEN 32 AND 33. LARGE RAIN SHIELD EXTENDS BACK INTO IL SO EXPECT
THIS TO CONTINUE NEXT SEVERAL HOURS. DRY SLOT WORKS IN AFTER
DAYBREAK BUT ENOUGH LOW LEVEL RESIDUAL MOISTURE TO SUPPORT FREEZING
DRIZZLE OR FLURRIES WITH VIS RESTRICTIONS DUE TO BR. LAKE EFFECT
SNOW BAND EXPECTED TO SET UP LATE THIS AFTERNOON INTO EARLY EVENING.
HAVE ONLY TAKEN SBN VIS DOWN TO 3SM -SN FOR NOW GIVEN UNCERTAINTY OF
WHERE BAND WILL BE. VERY LIKELY MUCH LOWER RESTRICTIONS AND POSSIBLE
HEAVY SNOW WILL BE NEEDED FROM BETWEEN 03Z AND 12Z TUE. MORE
REFINEMENT IN LATER ISSUANCES.
&&
.UPDATE...
GETTING 1/8" GLAZING REPORTS ON TREES JUST NORTH OF SOUTH BEND LATE
THIS EVE. BASED ON SFC OBS EXPECT SIMILAR CONDITIONS THROUGHOUT THE
ADVISORY AREA WITH THE PSBL EXCEPTION OF URBAN AREAS OF SOUTH
BEND/ELKHART DECIDED TO UPGRADE FREEZING RAIN ADVISORY TO AN ICE
STORM WARNING. ALSO GETTING SCT REPORTS OF ICING FARTHER SOUTH AND
WITH DFI TEMP AT 32 LAST SEVERAL HOURS AND FWA TEMP/DWPT FALLING
SLOWLY, WILL ISSUE FREEZING RAIN ADVISORY AREA SOUTH OF ICE STORM
WARNING A COUPLE TIERS OF COUNTIES. EXPECT ICING IN THIS AREA WILL
MAINLY BE ON ELEVATED SURFACES, BUT STILL COULD BE SUFFICIENT TO
CAUSE SOME PROBLEMS.
&&
.PREV DISCUSSION...
PREVIOUS UPDATE...
EVE RAOB/TAMDAR SOUNDINGS SHOWING WARM LAYER OF GENERALLY +2 TO +6C
OVER OUR AREA RESULTING IN INITIAL PRECIP REACHING THE GROUND AS
RN/ZR. SFC OBS AND CALLS TO POLICE IN THE AREA INDICATE SO FAR ONLY
PATCHY REPORTS OF GLAZING IN NRN INDIANA AND NW OH EVEN THOUGH SOME
ASOS/AWOS SITES REPORTING TEMPS AT FREEZING. THIS PRBLY A RESULT OF
TEMPERATURE OF HEAVY RAINFALL GENERALLY REACHING THE GROUND ABOVE
FREEZING. IN MICHIGAN WHERE SFC TEMPS HAVE BEEN RUNNING A DEGREE OR
TWO BELOW FREEZING ALL DAY AND THIS EVE, MORE WIDESPREAD GLAZING IS
BEING REPORTED. WITH WAA OVERNIGHT AS SFC LOW MOVES NE FROM SRN MO
TO WEST CENTRAL OH, THE RN/SN LINE, WHICH IS EXPECTED TO SETUP FROM
JUST NORTH OF CHICAGO TO JUST NORTH OF DETROIT THIS EVE, WILL PRBLY
SHIFT SLIGHTLY NORTH. THUS, AS IN GOING FCST STILL EXPECTING A
MAINLY LIQUID EVENT WITH MAIN THREAT FOR ICE ACCUMULATIONS ACROSS
OUR NRN COUNTIES. MAIN QUESTIONS ARE HOW MUCH OF THE HEAVY RAIN WILL
ACCUMULATE AS ICE IN THE ADVISORY AREAS AND IF SFC TEMPS WILL FALL
SUFFICIENTLY SOUTH OF THE ADVISORY AREA TO WARRANT EXPANSION. FOR
NOW FEEL THINGS ARE ON TRACK AND WILL CONTINUE TO MONITOR BUT NO
CHANGES TO HEADLINES OR FCSTS PLANNED THIS EVE.
SHORT TERM...
TONIGHT AND MONDAY.
...SIGNIFICANT ICING EXPECTED ACROSS SOUTHERN LOWER MICHIGAN TONIGHT
INTO MONDAY MORNING...
...SOME ICING EXPECTED ACROSS NORTHERN INDIANA AND NORTHWEST OHIO
TONIGHT AND MONDAY...
12Z NAM-WRF AND 12Z GFS CONTINUE TO TREND NEXT WAVE OF LOW PRESSURE
FARTHER NORTHWEST. THE NAM-WRF IS THE FARTHEST NORTHWEST OF THE
TWO...PLACING THE WAVE OF LOW PRESSURE OVER NW OHIO BY 12Z MONDAY.
BASED ON THE TREND OF BRINGING THE LOW FARTHER NORTHWEST...FEEL MORE
INCLINED TO SIDE WITH THE NAM-WRF AND THUS WILL USE ITS SOLUTION AS
A BACKBONE TO THE SHORT TERM FORECAST. ITS WARMER THERMAL PROFILE
WILL RESULT IN MOSTLY FREEZING RAIN TONIGHT ACRS THE NRN CWFA.
AT 20Z...LOW PRESSURE WAS DEVELOPING ALONG A STATIONARY FRONT OVER
NW ARKANSAS. AS A STRONG S/WV AND JET PIVOT NORTHEAST INTO THE
CNTRL PLAINS TONIGHT AND THEN INTO THE WRN GREAT LAKES ON
MONDAY...THE LOW WILL MOVE NORTHEAST AND DEEPEN WITH TIME...BEING
LOCATED NEAR SW INDIANA AT 06Z MONDAY AND NEAR NW OHIO BY 12Z MONDAY.
THE LOW WILL BE ASSOCIATED WITH STRONG...MOIST LOW LVL WARM
ADVECTION. THIS STRONG ASCENT WILL TEAM UP WITH UPR LVL DIVERGENCE
FROM A STRONG JET ALOFT. THIS WILL RESULT IN WIDESPREAD PCPN ACRS
THE CWFA OVERNIGHT. IN FACT...LATEST MOSAIC RADAR WAS SHOWING A
LARGE AREA OF PCPN BLOSSOMING ACRS THE CNTRL AND SRN PLAINS. THIS
PCPN WILL CONTINUE TO EXPAND AND MOVE NE INTO THE REGION TONIGHT.
THERE IS A LOT TO BE CONCERNED ABOUT OVERNIGHT INTO THE FIRST PART
OF MONDAY AS COLD AIR REMAINS TRAPPED NEAR THE SFC ACRS THE FAR NRN
CWFA. LATEST OBSERVATIONS SHOW TEMPS HOVERING BETWEEN 30 AND 33
DEGREES ACRS FAR NRN INDIANA...SOUTHERN LOWER MICHIGAN AND FAR
NORTHWEST OHIO. THESE TEMPS WILL NOT BUDGE MUCH OVERNIGHT...AND MAY
SLIGHTLY DROP A DEGREE OR TWO. FOR THE REMAINDER OF THE
REGION...TEMPS WILL REMAIN STEADY STATE IN THE LOWER TO MID
30S...EXPECT FOR THE FAR SOUTHEAST WHERE WARMER AIR WILL BE PULLED
WESTWARD AS THE LOW APPROACHES. WITH ABOUT THREE QUARTERS TO
AROUND ONE INCH OF QPF EXPECTED OVERNIGHT...SIGNIFICANT ICING WILL
OCCUR ACRS THE MICHIGAN COUNTIES WHERE ABOUT A HALF INCH OF ICE
ACCUMULATION IS EXPECTED. FOR THE FAR NRN INDIANA AND NORTHWEST
OHIO COUNTIES...ICE ACCUMULATIONS WILL BE LESS THAN A QUARTER INCH.
FARTHER SOUTH...MAINLY RAIN IS EXPECTED. AN ICE STORM WARNING WILL
BE ISSUED FOR THE MICHIGAN COUNTIES UNTIL 17Z MONDAY...WHILE A
FREEZING RAIN ADVISORY WILL BE ISSUED FOR THE FAR NRN INDIANA/NW
OHIO COUNTIES THROUGH 17Z MONDAY. ADDITIONAL RAINFALL ACRS THE FAR
SOUTH/SOUTHEAST WILL LIKELY LEAD TO RIVER FLOODING ALONG THE UPPER
WABASH AND MAUMEE RIVER BASINS..SO WILL MAINTAIN FLOOD WATCH FOR
THIS LOCATION THROUGH 18Z MONDAY.
ON MONDAY...AS SFC LOW PRESSURE PULLS AWAY TO THE NE...COLDER AIR
WILL BEGIN TO FILTER SE INTO THE FCST AREA. THERE WILL LIKELY BE
FREEZING PCPN ACRS THE NW HALF OF THE CWFA...BUT THIS SHOULD BE ON
THE LIGHT SIDE. FOR THE SOUTHEAST...LIGHT RAIN IS EXPECTED. MODELS
CONTINUE TO SHOW A DRY SLOT WORKING INTO THE REGION BY MID MORNING.
THIS MAY CHC PCPN TO DRIZZLE OR FREEZING DRIZZLE. HAVE OPTED TO GO
WITH THE LIGHT FREEZING RAIN/LIGHT RAIN WORDING DUE TO LINGER PCPN
EARLY IN THE MORNING IN ASSOCIATION WITH THE LOW AND FOR THE FACT
THAT SOME OF THE DRIZZLE MAY MEASURE. AS COLDER AIR AND DEEPER
ATMOSPHERIC MOISTURE FILTER INTO THE REGION DURING THE
AFTERNOON...ANY DRIZZLE WILL CHANGEOVER TO SOME LIGHT SNOW. MAIN
LAKE EFFECT EVENT LOOKS TO HOLD OFF UNTIL MONDAY NIGHT AND WILL
LEAVE THOSE DETAILS TO THE LONG TERM FORECASTER.
LONG TERM...
MONDAY NIGHT THROUGH SUNDAY
...SIGNIFICANT LAKE EFFECT SNOW POSSIBLE MONDAY NIGHT THROUGH
TUESDAY...
MAIN CONCERN FOR THE LONG TERM TODAY REVOLVES AROUND LAKE EFFECT
POTENTIAL AT THE START OF THE PERIOD. MODERATE LOW/MID LEVEL CAA
FOLLOWING MAJOR FRONTAL WAVE ON MON WILL BRING MUCH COLDER AIR
ACROSS THE LAKE WITH AMPLE LAKE INSTABILITY DEVELOPING. NEAR RECORD
WARM LAKE TEMPERATURE OF AROUND 5C PER LATEST SATELLITE DERIVED DATA
WILL CONTRIBUTE TO MODERATE COLLIER INDEX WITH LAKE INDUCED CAPE
AROUND 500J/KG AND LAKE INDUCED EQUILIBRIUM LEVELS AROUND 10K FEET.
INSTABILITY IS CERTAINLY MORE THAN AMPLE...HOWEVER MUCH UNCERTAINTY
LIES WITH BAND MODE...PLACEMENT...AND AMOUNT OF SHEAR. FROM A
PATTERN RECOGNITION PROSPECTIVE...SETUP LOOKS VERY FAVORABLE WITH A
1040+MB HIGH BUILDING SOUTH THROUGH THE PLAINS AND FAVORABLE N/NNW
FLOW DEVELOPING DOWN A SUBSTANTIAL FETCH OF LAKE MICHIGAN. A
POTENTIAL NEGATIVE...BOTH NAM/GFS SUGGEST THERE WILL BE SOME SHEAR
NEAR THE TOP OF THE LAKE INDUCED MIXED LAYER WITH A MORE WESTERLY
COMPONENT AT 700MB AND MORE NW/NNW AT 850MB. NAM-WRF PLUME ANALYSIS
CONTINUES TO SUGGEST THE POTENTIAL FOR A TYPE I LAKE EFFECT
BAND...MEANING A DOMINANT BAND PARALLEL TO THE MAJOR AXIS OF THE
LAKE.
NAM-WRF HAS BEEN FLIP-FLOPPING WILDLY FROM RUN TO RUN WITH RESPECT
TO DIRECTION OF LOW LEVEL FLOW...WITH 00Z AND 06Z RUNS SUGGESTING A
NEAR DUE NORTH FETCH...WHILE 12Z RUN SUGGESTS MORE NW FETCH. A LOOK
AT SOME OTHER MESOSCALE GUIDANCE SUCH AS THE FSL EXPERIMENTAL RUC
AND THE CANADIAN GEM SHOW MORE UNCERTAINTY...WITH BOTH THOSE MODELS
DEPICTING MORE NORTHERLY FLOW AND A MORE WESTWARD BAND PLACEMENT.
TYPICAL BIAS OF MESOSCALE MODELS ARE TO BE TOO FAR WEST WITH A
DOMINANT BAND AT THE SOUTHERN END OF LAKE MICHIGAN. WITH THE VERY
POOR MODEL AGREEMENT AND CONSISTENCY...JUST NOT ENOUGH CONFIDENCE
ON BAND PLACEMENT OR MODE TO GO WITH AN LES WATCH YET. STILL ENOUGH
TIME FOR A SHORTER RANGE WATCH FROM THE MIDNIGHT SHIFT IF MODEL
GUIDANCE STARTS TO CONVERGE ON A COMMON SOLUTION. THIS DOES HAVE THE
POTENTIAL TO BE A MAJOR EVENT GIVEN STRONG THERMODYNAMICS...BUT ONLY
IF A DOMINANT BAND FORMS...AND THAT IS STILL QUITE UNCERTAIN.
CP SURFACE HIGH BUILDS ACROSS THE OHIO VALLEY LATER TUE NGT INTO WED
WITH CRASHING INVERSION HEIGHTS AND BACKING LOW LEVEL FLOW CUTTING
OFF ANY REMAINING LAKE EFFECT. SHOULD SEE A DRY PERIOD FOR WED AND
THU WITH A MODERATING TREND AS HEIGHTS RISE IN RESPONSE TO DIGGING
UPSTREAM TROUGH. VERY LITTLE CHANGE MADE TO CONTINUITY IN THE LATER
PERIODS WITH PRIMARY CONCERNS IN SHORT TERM HIGH IMPACT WEATHER.
STILL APPEARS THAT ONE OR SEVERAL CLIPPER TYPE SHORTWAVES WILL CROSS
THE GREAT LAKES STARTING AT THE END OF THE WEEK AND HAVE CONTINUED
WITH LOW CHANCE POPS...MAINLY ACROSS THE NORTHERN PORTION OF THE
CWA. TEMPS WILL AVERAGE AROUND NORMAL FOR MUCH OF THE LONG TERM...
BUT THIS WILL FEEL COLD AFTER THE INCREDIBLE STRETCH OF WARM WEATHER
THE PAST MONTH.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FLOOD WATCH THROUGH MONDAY AFTERNOON FOR INZ020-INZ022-INZ023-
INZ024-INZ025-INZ026-INZ027-INZ032-INZ033-INZ034.
FREEZING RAIN ADVISORY UNTIL 12 PM EST /11 AM CST/ MONDAY FOR
INZ008-INZ009-INZ012-INZ013-INZ014-INZ015-INZ016-INZ017-
INZ018.
ICE STORM WARNING UNTIL 12 PM EST /11 AM CST/ MONDAY FOR INZ003-
INZ004-INZ005-INZ006-INZ007.
MI...ICE STORM WARNING UNTIL 12 PM EST MONDAY FOR MIZ077-MIZ078-
MIZ079-MIZ080-MIZ081.
OH...FLOOD WATCH THROUGH MONDAY AFTERNOON FOR OHZ016-OHZ024-OHZ025.
FREEZING RAIN ADVISORY UNTIL 12 PM EST MONDAY FOR OHZ004-OHZ005-
OHZ015.
ICE STORM WARNING UNTIL 12 PM EST MONDAY FOR OHZ001-OHZ002.
LM...SMALL CRAFT ADVISORY UNTIL 5 PM EST TUESDAY FOR LMZ043-LMZ046.
$$
AVIATION/UPDATE...LASHLEY/TAYLOR
SHORT TERM...HICKMAN
LONG TERM....HITCHCOCK
AREA FORECAST DISCUSSION...UPDATED
NWS JACKSON KY
AFDJKL 403 AM EST MON JAN 15 2007
.SHORT TERM.../TODAY THROUGH WEDNESDAY NIGHT/
PRIMARY FORECAST PROBLEM IS TIMING OF PRECIP ONSET AND EASTWARD
PROGRESSION OF COLD FRONT LATER TODAY. BASED ON TRENDS OF PAST 24
HOURS AND LATEST MODEL RUNS...DECIDED TO DELAY ONSET OF PRECIP BY A
FEW HOURS...WITH MAIN AREA OF RAIN SHOWERS NOT MOVING INTO JKL/LOZ
UNTIL 15Z OR SO. INCORPORATED THIS NEW SLOWER TREND INTO FORECAST
THROUGH 9Z TUESDAY TO ACCOUNT FOR EXPECTED SLOWER MOVEMENT OF FRONT.
WENT ABOVE HIGHEST MOS NUMBERS FOR TODAYS HIGHEST PRECIP
CHANCES...ESPECIALLY ALONG AND JUST BEHIND THE FRONT AS IT TRAVERSES
THE CWA LATER TODAY.
WITH COLDER AIR FILTERING LATER TONIGHT BEHIND FRONT...STILL
ANTICIPATE A FEW SNOW SHOWERS COULD MIX WITH RAIN LATER THIS
EVENING...WITH A TRANSITION TO ALL SNOW AFTER MIDNIGHT.
HOWEVER...INSPITE OF GOOD LOW LEVEL MOISTURE...A GOOD DEAL OF DRY
AIR IS FORECAST TO INFILTRATE THE MID LEVELS OF THE ATMOSPHERE
BEHIND FRONT. WITH THIS IN MIND...NOT ANTICIPATING WIDESPREAD SNOW
OR MUCH IN THE WAY OF ACCUMULATION. THE EXCEPTION BEING THE HIGHER
ELEVATIONS ALONG THE VIRGINIA BORDER...WHERE A DUSTING UP TO AN
INCH OF SNOW COULD FALL. IT APPEARS AT THIS TIME THAT SCATTERED
LIGHT SNOW SHOWERS AND FLURRIES WILL BE THE PRIMARY TYPE OF PRECIP
TO FALL AS SHORTWAVE MOVES QUICKLY ACROSS THE CWA LATER TONIGHT.
MADE CORRESPONDING CHANGES TO SKY COVER GRIDS...TO ACCOUNT FOR
SLOWER EASTWARD MOVEMENT OF FRONT. ALSO ADJUSTED QPF AND WEATHER
GRIDS BASED ON CHANGES MADE TO POPS AND SKY COVER. WINDS WERE IN
PRETTY GOOD SHAPE...BUT NEEDED TO BE CHANGED TO MATCH UP WITH SLOWER
FRONTAL MOVEMENT. WITH LESS CLOUD COVER AND A MORE PROLONGED PERIOD
OF SOUTHERLY FLOW ANTICIPATED THROUGH THE MORNING HOURS...COUPLED
WITH A SLOWER EASTWARD MOVEMENT OF THE FRONT...DECIDED TO GO ABOVE
THE WARMEST MOS NUMBERS FOR TODAYS HIGH TEMPERATURES. DEWPOINTS WERE
IN PRETTY GOOD SHAPE OVERALL. DID HAVE TO TWEAK DEWPOINT NUMBERS FOR
THURSDAY...AS PREVIOUS DEW TEMPS WERE A BIT TO HIGH. ADJUSTED DOWN
TOWARD LATEST MEXMOS DEWPOINTS...WITH A SLOW INCREASE IN DEWPOINTS
IN SOUTHWESTERN COUNTIES...AS ANOTHER AREA OF LOW PRESSURE
APPROACHES FROM THE WEST LATE WEDNESDAY INTO THURSDAY.
THE REST OF THE PREVIOUS DISCUSSION FOLLOWS:
THE MODELS ARE IN GOOD AGREEMENT ALOFT THROUGH 48 HOURS AS THEY TAKE
THE BULK OF THE LARGE SOUTHWEST TROUGH...PICKED UP BY THE NORTHERN
STREAM...AND RAM IT INTO THE NORTHERN FRINGE OF THE ANOMALOUS
SOUTHEASTERN RIDGE BY TUESDAY MORNING. THIS COLLISION TAKES PLACE
OVER THE OHIO VALLEY AND WILL BE THE KEY FACTOR FINALLY SHOVING THE
STALLED SFC FRONTAL BOUNDARY THROUGH KENTUCKY AND OFF TO THE
SOUTHEAST. AFTER 48 HOURS THE MODELS DIVERGE SOMEWHAT AS THE GFS
HOLDS BACK A BIGGER CHUNK OF THE SOUTHWEST LOW THAN THE NAM...THOUGH
THE PROGS ARE SIMILAR OVER THE EASTERN HALF OF THE NATION. IN THE
WAKE OF THE NORTHEAST TROUGH SWEEPING THROUGH...HEIGHTS WILL RISE
OVER THE OHIO VALLEY THROUGH MID WEEK. HOWEVER...THE DIFFERENCE IN
THE MODEL SOLUTIONS IN THE WEST WILL LEAD TO MORE UNCERTAINTY FOR THE
EXTENDED PART OF THE FORECAST.
SENSIBLE WEATHER WILL FEATURE A RENEWED SURGE OF MOISTURE AND LIFT
ALONG THE FRONT TONIGHT AS THE MAIN WAVE APPROACHES. STILL THINK THAT
THERE WILL BE A TIGHT GRADIENT TO THE RAIN CHANCES FROM NORTHWEST TO
SOUTHEAST ACROSS THE CWA...THOUGH...AND HAVE TRIED TO SHOW THIS IN
THE GRIDS AND TEXT PRODUCTS. IN GENERAL...HAVE FOLLOWED A BLEND OF
THE SIMILAR MODEL SOLUTIONS. ACCORDINGLY...EXPECT THE DEEPENING SFC
LOW TO LIFT THE EASTERN PORTION OF THE STALLED FRONT NORTHWARD THIS
EVENING AS THE LOW APPROACHES...KEEPING THE SOUTHEAST TWO THIRDS OF
THE CWA FROM SEEING MUCH IN THE WAY OF RAINFALL UNTIL THE COLD FRONT
COMES THROUGH MONDAY MORNING. THIS FRONT WILL CONTAIN HEAVY TO
EXCESSIVE RAINS ENHANCED BY STRONG SFC CONVERGENCE. EXPECT A SOLID
INCH OF RAIN FOR MOST OF THE AREA AS IT MOVES THROUGH DURING THE DAY
MONDAY. NORTH OF THE MOUNTAIN PARKWAY...IN THE WATCH AREA...THEY ARE
A LITTLE MORE PRIMED FOR FLASH FLOODING DUE TO THE RAIN THAT THEY SAW
LAST NIGHT. ACCORDINGLY...THE WATCH FOR THIS AREA REMAINS A GOOD
IDEA...THOUGH THE THREAT FOR SIGNIFICANT RIVER RISES AND POTENTIAL
FOR LARGER TRIBUTARY FLOODING APPEARS TO BE MUCH DIMINISHED. HAVE
ADJUSTED THE WORDING IN THE FFA TO REFLECT THESE LATEST THOUGHTS.
WITH THE FRONT NOT DUE IN HERE UNTIL AFTER 12Z...HAVE KEEP TEMPS UP
QUITE MILD TONIGHT AND THEN USED THESE AS A STARTING POINT FOR HIGHS
ON MONDAY WITH FALLING TEMPS EXPECTED DURING THE AFTERNOON.
THE COLDER...MODIFIED ARCTIC AIR MOVES INTO THE AREA MONDAY NIGHT...
CHANGING THE LINGERING PCPN FROM RAIN SHOWERS TO SNOW SHOWERS. ON
TUESDAY...UPSLOPE FLOW AND THE UPPER LEVEL DYNAMICS OF THE TROUGH
PASSING WILL KEEP THE CHANCE FOR MAINLY SNOW SHOWERS IN THE FORECAST
THROUGH THE DAY AND INTO TUESDAY NIGHT. DO NOT SEE ENOUGH QPF
AVAILABLE FOR ANY ACCUMULATION FROM THESE SHOWERS...THOUGH.
HOWEVER...THE COLDER AIR AND BRISK NORTHWEST WINDS WILL HELP TO
PUNCTUATE THIS SHARP RETURN TO MORE SEASONABLE WEATHER.
.LONG TERM.../WEDNESDAY THROUGH SATURDAY/
THE MODELS HAVE A FAIR AMOUNT OF DISAGREEMENT ALOFT THROUGH THE
EXTENDED PORTION OF THE FORECAST WITH THE OUTLIER GFS MAINTAINING A
STRONGER SOUTHEAST RIDGE THAN THE OTHER MODELS. ACCORDINGLY...HAVE
BLENDED TOWARD THE LESS AMPLIFIED...NORTHERN STREAM DOMINATED...
SOLUTION OF THE ECMWF FOR THE FORECAST. THE HPC PRESSURE AND SFC
FRONTAL PROGS WERE FOLLOWED CLOSELY FOR THIS FORECAST. LIKEWISE...
THEIR TEMPERATURES GUIDANCE WAS ACCEPTED WITH MINOR ADJUSTMENTS MADE
FOR LOCAL TERRAIN EFFECTS. AS FOR SENSIBLE WEATHER...MUCH MORE
SEASONABLE WEATHER WILL BE UPON US AS MODERATED ARCTIC HIGH PRESSURE
PUSHES THROUGH THE MIDWEST AND INTO THE OHIO VALLEY. MEANWHILE...THE
BOUNDARY THAT BROUGHT RAIN AND SHOW SHOWERS TO THE FIRST PART OF THE
FORECAST WILL STALL WELL TO THE SOUTHEAST. HOWEVER...A NORTHERN
STREAM WAVE WILL LURE MORE MOISTURE NORTH AHEAD OF ITS SFC
TROUGH...STARTING THURSDAY. THIS RETURN FLOW MOISTURE WILL MAKE THE
FORECAST FOR THE END OF THE WEEK TRICKY...PARTICULARLY IN THE FACE OF
MODEL DISAGREEMENT ALOFT OVER OUR REGION. FOR NOW HAVE GONE WITH A
SMALL CHANCE FOR RAIN OR SNOW STARTING LATE THURSDAY NIGHT AND
CONTINUING THROUGH THE WEEKEND AS DEEP LOW PRESSURE PASSES BY TO THE
NORTH LATE FRIDAY. ANOTHER SYSTEM AND ITS COLD FRONT WILL QUICKLY
APPROACH THE AREA LATER SATURDAY SWINGING THROUGH ON SUNDAY. WITHOUT
THE NORTHERN AND SOUTHERN STREAM PHASING OVERALL PCPN AMOUNTS LOOK TO
BE LIGHT THROUGH THE LATTER PART OF THE FORECAST.
&&
.AVIATION.../06Z TO 06Z/...UPDATED
SURFACE LOW IS MOVING NORTH UP THE LOWER OHIO VALLEY ALONG A SURFACE
BOUNDARY DRAPED ACROSS SOUTHERN ILLINOIS...INDIANA AND OHIO. THE
TRACK OF THE SURFACE LOW WILL KEEP EAST KENTUCKY IN THE WARM SECTOR
WITH VFR CONDITIONS EXPECTED THROUGH AROUND 14Z. MODELS CONTINUE TO
INDICATE A STRENGTHENING LOW LEVEL JET TOWARDS DAWN...ALTHOUGH THEIR
PROJECTIONS MAYBE SLIGHTLY OVERDONE COMPARING THE PROGS WITH
OBSERVED ACARS SOUNDINGS OVER SDF. NEVERTHELESS...EXPECT MARGINAL
LLWS TO BE OBSERVED BY 10Z WITH SPEEDS OF 40 KT AS LOW AS 1500 FT
AGL.
AS THE SURFACE LOW TRACKS OFF TO OUR NORTHEAST...THE LONG AWAITING
COLD FRONTAL PASSAGE WILL FINALLY TAKE PLACE BRINGING A PERIOD OF
SHRA/+SHRA WITH AT LEAST MVFR CIGS AND VSBYS. WOULD EXPECT SOME
BRIEF IFR CONDITIONS AS WELL BUT NOT LONG ENOUGH TO INCLUDE IN TAFS
AT THIS TIME. SOUTHWESTERLY WINDS WILL ALSO INCREASE AS THE FRONT
NEARS WITH GUSTS OVER 20 KT EXPECTED. THE WINDS WILL VEER AROUND
BECOMING WESTERLY AFTER THE FROPA WITH SHRA GRADUALLY DECREASING IN
COVERAGE. PLENTIFUL LOW LEVEL MOISTURE BEHIND THE FRONT SHOULD KEEP
MVFR CIGS AROUND THROUGH THE END OF THE TAF PERIOD.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH THROUGH MONDAY AFTERNOON FOR KYZ044-050>052-058>060-
104-106-108.
&&
$$
SHORT TERM...AR
LONG TERM...GREIF
AVIATION...ABE
AREA FORECAST DISCUSSION
NWS JACKSON KY
AFDJKL 358 AM EST MON JAN 15 2007
.SHORT TERM.../TODAY THROUGH WEDNESDAY NIGHT/
PRIMARY FORECAST PROBLEM IS TIMING OF PRECIP ONSET AND EASTWARD
PROGRESSION OF COLD FRONT LATER TODAY. BASED ON TRENDS OF PAST 24
HOURS AND LATEST MODEL RUNS...DECIDED TO DELAY ONSET OF PRECIP BY A
FEW HOURS...WITH MAIN AREA OF RAIN SHOWERS NOT MOVING INTO JKL/LOZ
UNTIL 15Z OR SO. INCORPORATED THIS NEW SLOWER TREND INTO FORECAST
THROUGH 9Z TUESDAY TO ACCOUNT FOR EXPECTED SLOWER MOVEMENT OF FRONT.
WENT ABOVE HIGHEST MOS NUMBERS FOR TODAYS HIGHEST PRECIP
CHANCES...ESPECIALLY ALONG AND JUST BEHIND THE FRONT AS IT TRAVERSES
THE CWA LATER TODAY.
MADE CORRESPONDING CHANGES TO SKY COVER GRIDS...TO ACCOUNT FOR
SLOWER EASTWARD MOVEMENT OF FRONT. ALSO ADJUSTED QPF AND WEATHER
GRIDS BASED ON CHANGES MADE TO POPS AND SKY COVER. WINDS WERE IN
PRETTY GOOD SHAPE...BUT NEEDED TO BE CHANGED TO MATCH UP WITH SLOWER
FRONTAL MOVEMENT. WITH LESS CLOUD COVER AND A MORE PROLONGED PERIOD
OF SOUTHERLY FLOW ANTICIPATED THROUGH THE MORNING HOURS...COUPLED
WITH A SLOWER EASTWARD MOVEMENT OF THE FRONT...DECIDED TO GO ABOVE
THE WARMEST MOS NUMBERS FOR TODAYS HIGH TEMPERATURES. DEWPOINTS WERE
IN PRETTY GOOD SHAPE OVERALL. DID HAVE TO TWEAK DEWPOINT NUMBERS FOR
THURSDAY...AS PREVIOUS DEW TEMPS WERE A BIT TO HIGH. ADJUSTED DOWN
TOWARD LATEST MEXMOS DEWPOINTS...WITH A SLOW INCREASE IN DEWPOINTS
IN SOUTHWESTERN COUNTIES...AS ANOTHER AREA OF LOW PRESSURE
APPROACHES FROM THE WEST LATE WEDNESDAY INTO THURSDAY.
THE REST OF THE PREVIOUS DISCUSSION FOLLOWS:
THE MODELS ARE IN GOOD AGREEMENT ALOFT THROUGH 48 HOURS AS THEY TAKE
THE BULK OF THE LARGE SOUTHWEST TROUGH...PICKED UP BY THE NORTHERN
STREAM...AND RAM IT INTO THE NORTHERN FRINGE OF THE ANOMALOUS
SOUTHEASTERN RIDGE BY TUESDAY MORNING. THIS COLLISION TAKES PLACE
OVER THE OHIO VALLEY AND WILL BE THE KEY FACTOR FINALLY SHOVING THE
STALLED SFC FRONTAL BOUNDARY THROUGH KENTUCKY AND OFF TO THE
SOUTHEAST. AFTER 48 HOURS THE MODELS DIVERGE SOMEWHAT AS THE GFS
HOLDS BACK A BIGGER CHUNK OF THE SOUTHWEST LOW THAN THE NAM...THOUGH
THE PROGS ARE SIMILAR OVER THE EASTERN HALF OF THE NATION. IN THE
WAKE OF THE NORTHEAST TROUGH SWEEPING THROUGH...HEIGHTS WILL RISE
OVER THE OHIO VALLEY THROUGH MID WEEK. HOWEVER...THE DIFFERENCE IN
THE MODEL SOLUTIONS IN THE WEST WILL LEAD TO MORE UNCERTAINTY FOR THE
EXTENDED PART OF THE FORECAST.
SENSIBLE WEATHER WILL FEATURE A RENEWED SURGE OF MOISTURE AND LIFT
ALONG THE FRONT TONIGHT AS THE MAIN WAVE APPROACHES. STILL THINK THAT
THERE WILL BE A TIGHT GRADIENT TO THE RAIN CHANCES FROM NORTHWEST TO
SOUTHEAST ACROSS THE CWA...THOUGH...AND HAVE TRIED TO SHOW THIS IN
THE GRIDS AND TEXT PRODUCTS. IN GENERAL...HAVE FOLLOWED A BLEND OF
THE SIMILAR MODEL SOLUTIONS. ACCORDINGLY...EXPECT THE DEEPENING SFC
LOW TO LIFT THE EASTERN PORTION OF THE STALLED FRONT NORTHWARD THIS
EVENING AS THE LOW APPROACHES...KEEPING THE SOUTHEAST TWO THIRDS OF
THE CWA FROM SEEING MUCH IN THE WAY OF RAINFALL UNTIL THE COLD FRONT
COMES THROUGH MONDAY MORNING. THIS FRONT WILL CONTAIN HEAVY TO
EXCESSIVE RAINS ENHANCED BY STRONG SFC CONVERGENCE. EXPECT A SOLID
INCH OF RAIN FOR MOST OF THE AREA AS IT MOVES THROUGH DURING THE DAY
MONDAY. NORTH OF THE MOUNTAIN PARKWAY...IN THE WATCH AREA...THEY ARE
A LITTLE MORE PRIMED FOR FLASH FLOODING DUE TO THE RAIN THAT THEY SAW
LAST NIGHT. ACCORDINGLY...THE WATCH FOR THIS AREA REMAINS A GOOD
IDEA...THOUGH THE THREAT FOR SIGNIFICANT RIVER RISES AND POTENTIAL
FOR LARGER TRIBUTARY FLOODING APPEARS TO BE MUCH DIMINISHED. HAVE
ADJUSTED THE WORDING IN THE FFA TO REFLECT THESE LATEST THOUGHTS.
WITH THE FRONT NOT DUE IN HERE UNTIL AFTER 12Z...HAVE KEEP TEMPS UP
QUITE MILD TONIGHT AND THEN USED THESE AS A STARTING POINT FOR HIGHS
ON MONDAY WITH FALLING TEMPS EXPECTED DURING THE AFTERNOON.
THE COLDER...MODIFIED ARCTIC AIR MOVES INTO THE AREA MONDAY NIGHT...
CHANGING THE LINGERING PCPN FROM RAIN SHOWERS TO SNOW SHOWERS. ON
TUESDAY...UPSLOPE FLOW AND THE UPPER LEVEL DYNAMICS OF THE TROUGH
PASSING WILL KEEP THE CHANCE FOR MAINLY SNOW SHOWERS IN THE FORECAST
THROUGH THE DAY AND INTO TUESDAY NIGHT. DO NOT SEE ENOUGH QPF
AVAILABLE FOR ANY ACCUMULATION FROM THESE SHOWERS...THOUGH.
HOWEVER...THE COLDER AIR AND BRISK NORTHWEST WINDS WILL HELP TO
PUNCTUATE THIS SHARP RETURN TO MORE SEASONABLE WEATHER.
.LONG TERM.../WEDNESDAY THROUGH SATURDAY/
THE MODELS HAVE A FAIR AMOUNT OF DISAGREEMENT ALOFT THROUGH THE
EXTENDED PORTION OF THE FORECAST WITH THE OUTLIER GFS MAINTAINING A
STRONGER SOUTHEAST RIDGE THAN THE OTHER MODELS. ACCORDINGLY...HAVE
BLENDED TOWARD THE LESS AMPLIFIED...NORTHERN STREAM DOMINATED...
SOLUTION OF THE ECMWF FOR THE FORECAST. THE HPC PRESSURE AND SFC
FRONTAL PROGS WERE FOLLOWED CLOSELY FOR THIS FORECAST. LIKEWISE...
THEIR TEMPERATURES GUIDANCE WAS ACCEPTED WITH MINOR ADJUSTMENTS MADE
FOR LOCAL TERRAIN EFFECTS. AS FOR SENSIBLE WEATHER...MUCH MORE
SEASONABLE WEATHER WILL BE UPON US AS MODERATED ARCTIC HIGH PRESSURE
PUSHES THROUGH THE MIDWEST AND INTO THE OHIO VALLEY. MEANWHILE...THE
BOUNDARY THAT BROUGHT RAIN AND SHOW SHOWERS TO THE FIRST PART OF THE
FORECAST WILL STALL WELL TO THE SOUTHEAST. HOWEVER...A NORTHERN
STREAM WAVE WILL LURE MORE MOISTURE NORTH AHEAD OF ITS SFC
TROUGH...STARTING THURSDAY. THIS RETURN FLOW MOISTURE WILL MAKE THE
FORECAST FOR THE END OF THE WEEK TRICKY...PARTICULARLY IN THE FACE OF
MODEL DISAGREEMENT ALOFT OVER OUR REGION. FOR NOW HAVE GONE WITH A
SMALL CHANCE FOR RAIN OR SNOW STARTING LATE THURSDAY NIGHT AND
CONTINUING THROUGH THE WEEKEND AS DEEP LOW PRESSURE PASSES BY TO THE
NORTH LATE FRIDAY. ANOTHER SYSTEM AND ITS COLD FRONT WILL QUICKLY
APPROACH THE AREA LATER SATURDAY SWINGING THROUGH ON SUNDAY. WITHOUT
THE NORTHERN AND SOUTHERN STREAM PHASING OVERALL PCPN AMOUNTS LOOK TO
BE LIGHT THROUGH THE LATTER PART OF THE FORECAST.
&&
.AVIATION.../06Z TO 06Z/...UPDATED
SURFACE LOW IS MOVING NORTH UP THE LOWER OHIO VALLEY ALONG A SURFACE
BOUNDARY DRAPED ACROSS SOUTHERN ILLINOIS...INDIANA AND OHIO. THE
TRACK OF THE SURFACE LOW WILL KEEP EAST KENTUCKY IN THE WARM SECTOR
WITH VFR CONDITIONS EXPECTED THROUGH AROUND 14Z. MODELS CONTINUE TO
INDICATE A STRENGTHENING LOW LEVEL JET TOWARDS DAWN...ALTHOUGH THEIR
PROJECTIONS MAYBE SLIGHTLY OVERDONE COMPARING THE PROGS WITH
OBSERVED ACARS SOUNDINGS OVER SDF. NEVERTHELESS...EXPECT MARGINAL
LLWS TO BE OBSERVED BY 10Z WITH SPEEDS OF 40 KT AS LOW AS 1500 FT
AGL.
AS THE SURFACE LOW TRACKS OFF TO OUR NORTHEAST...THE LONG AWAITING
COLD FRONTAL PASSAGE WILL FINALLY TAKE PLACE BRINGING A PERIOD OF
SHRA/+SHRA WITH AT LEAST MVFR CIGS AND VSBYS. WOULD EXPECT SOME
BRIEF IFR CONDITIONS AS WELL BUT NOT LONG ENOUGH TO INCLUDE IN TAFS
AT THIS TIME. SOUTHWESTERLY WINDS WILL ALSO INCREASE AS THE FRONT
NEARS WITH GUSTS OVER 20 KT EXPECTED. THE WINDS WILL VEER AROUND
BECOMING WESTERLY AFTER THE FROPA WITH SHRA GRADUALLY DECREASING IN
COVERAGE. PLENTIFUL LOW LEVEL MOISTURE BEHIND THE FRONT SHOULD KEEP
MVFR CIGS AROUND THROUGH THE END OF THE TAF PERIOD.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH THROUGH MONDAY AFTERNOON FOR KYZ044-050>052-058>060-
104-106-108.
&&
$$
SHORT TERM...AR
LONG TERM...GREIF
AVIATION...ABE
AREA FORECAST DISCUSSION
NWS JACKSON KY
AFDJKL 1245 AM EST MON JAN 15 2007
.SHORT TERM.../TONIGHT THROUGH TUESDAY NIGHT/
THE NW PART OF THE CWA RECEIVED SOME LIGHT PRECIP THIS EVENING FROM
SHOWERS...WITH RETURNS IN THE SOUTH NOT EVEN MEASURING. IN FACT...
ONLY A MID DECK IS IN PLACE IN MOST AREAS. SAT AND RADAR TRENDS...
AS WELL AS RECENT MODEL RUNS HAVE A LARGE BATCH OF RAIN IN ADVANCE
OF THE DEVELOPING SFC WAVE THAT IS RIDING NE ALONG THE FRONT
AFFECTING AREAS WELL WEST AND NW OF THE CWA FOR MOST OF THE NIGHT.
AS THE LOW GETS INTO OH LATER TONIGHT AND FRONT INCHES CLOSER TO THE
AREA...THE CHANCE FOR PRECIP ALONG THE FRONT WILL INCREASE. IN
ADDITION...SW/V TROUGH MOVING IN FROM THE WEST WILL ADD ADDITIONAL
FORCING FOR PRECIP...THAT HAS GENERALLY BEEN LACKING THIS EVENING
EVEN THOUGH PW IS 200 TO 350 PERCENT OF NORMAL.
THE 3 AND 6 HR FFG GUIDANCE VALUES REMAIN ABOUT 1.5 INCHES OR LESS
IN THE NW COUNTIES AND THOSE AMOUNTS MIGHT BE ATTAINABLE IN HEAVIER
SHOWERS LATER TONIGHT OR ON MONDAY...SO OPTED TO CONTINUE THE FLOOD
WATCH AS IS.
THE REST OF THE PREVIOUS DISCUSSION FOLLOWS:
THE MODELS ARE IN GOOD AGREEMENT ALOFT THROUGH 48 HOURS AS THEY TAKE
THE BULK OF THE LARGE SOUTHWEST TROUGH...PICKED UP BY THE NORTHERN
STREAM...AND RAM IT INTO THE NORTHERN FRINGE OF THE ANOMALOUS
SOUTHEASTERN RIDGE BY TUESDAY MORNING. THIS COLLISION TAKES PLACE
OVER THE OHIO VALLEY AND WILL BE THE KEY FACTOR FINALLY SHOVING THE
STALLED SFC FRONTAL BOUNDARY THROUGH KENTUCKY AND OFF TO THE
SOUTHEAST. AFTER 48 HOURS THE MODELS DIVERGE SOMEWHAT AS THE GFS
HOLDS BACK A BIGGER CHUNK OF THE SOUTHWEST LOW THAN THE NAM...THOUGH
THE PROGS ARE SIMILAR OVER THE EASTERN HALF OF THE NATION. IN THE
WAKE OF THE NORTHEAST TROUGH SWEEPING THROUGH...HEIGHTS WILL RISE
OVER THE OHIO VALLEY THROUGH MID WEEK. HOWEVER...THE DIFFERENCE IN
THE MODEL SOLUTIONS IN THE WEST WILL LEAD TO MORE UNCERTAINTY FOR THE
EXTENDED PART OF THE FORECAST.
SENSIBLE WEATHER WILL FEATURE A RENEWED SURGE OF MOISTURE AND LIFT
ALONG THE FRONT TONIGHT AS THE MAIN WAVE APPROACHES. STILL THINK THAT
THERE WILL BE A TIGHT GRADIENT TO THE RAIN CHANCES FROM NORTHWEST TO
SOUTHEAST ACROSS THE CWA...THOUGH...AND HAVE TRIED TO SHOW THIS IN
THE GRIDS AND TEXT PRODUCTS. IN GENERAL...HAVE FOLLOWED A BLEND OF
THE SIMILAR MODEL SOLUTIONS. ACCORDINGLY...EXPECT THE DEEPENING SFC
LOW TO LIFT THE EASTERN PORTION OF THE STALLED FRONT NORTHWARD THIS
EVENING AS THE LOW APPROACHES...KEEPING THE SOUTHEAST TWO THIRDS OF
THE CWA FROM SEEING MUCH IN THE WAY OF RAINFALL UNTIL THE COLD FRONT
COMES THROUGH MONDAY MORNING. THIS FRONT WILL CONTAIN HEAVY TO
EXCESSIVE RAINS ENHANCED BY STRONG SFC CONVERGENCE. EXPECT A SOLID
INCH OF RAIN FOR MOST OF THE AREA AS IT MOVES THROUGH DURING THE DAY
MONDAY. NORTH OF THE MOUNTAIN PARKWAY...IN THE WATCH AREA...THEY ARE
A LITTLE MORE PRIMED FOR FLASH FLOODING DUE TO THE RAIN THAT THEY SAW
LAST NIGHT. ACCORDINGLY...THE WATCH FOR THIS AREA REMAINS A GOOD
IDEA...THOUGH THE THREAT FOR SIGNIFICANT RIVER RISES AND POTENTIAL
FOR LARGER TRIBUTARY FLOODING APPEARS TO BE MUCH DIMINISHED. HAVE
ADJUSTED THE WORDING IN THE FFA TO REFLECT THESE LATEST THOUGHTS.
WITH THE FRONT NOT DUE IN HERE UNTIL AFTER 12Z...HAVE KEEP TEMPS UP
QUITE MILD TONIGHT AND THEN USED THESE AS A STARTING POINT FOR HIGHS
ON MONDAY WITH FALLING TEMPS EXPECTED DURING THE AFTERNOON.
THE COLDER...MODIFIED ARCTIC AIR MOVES INTO THE AREA MONDAY NIGHT...
CHANGING THE LINGERING PCPN FROM RAIN SHOWERS TO SNOW SHOWERS. ON
TUESDAY...UPSLOPE FLOW AND THE UPPER LEVEL DYNAMICS OF THE TROUGH
PASSING WILL KEEP THE CHANCE FOR MAINLY SNOW SHOWERS IN THE FORECAST
THROUGH THE DAY AND INTO TUESDAY NIGHT. DO NOT SEE ENOUGH QPF
AVAILABLE FOR ANY ACCUMULATION FROM THESE SHOWERS...THOUGH.
HOWEVER...THE COLDER AIR AND BRISK NORTHWEST WINDS WILL HELP TO
PUNCTUATE THIS SHARP RETURN TO MORE SEASONABLE WEATHER.
.LONG TERM.../WEDNESDAY THROUGH SATURDAY/
THE MODELS HAVE A FAIR AMOUNT OF DISAGREEMENT ALOFT THROUGH THE
EXTENDED PORTION OF THE FORECAST WITH THE OUTLIER GFS MAINTAINING A
STRONGER SOUTHEAST RIDGE THAN THE OTHER MODELS. ACCORDINGLY...HAVE
BLENDED TOWARD THE LESS AMPLIFIED...NORTHERN STREAM DOMINATED...
SOLUTION OF THE ECMWF FOR THE FORECAST. THE HPC PRESSURE AND SFC
FRONTAL PROGS WERE FOLLOWED CLOSELY FOR THIS FORECAST. LIKEWISE...
THEIR TEMPERATURES GUIDANCE WAS ACCEPTED WITH MINOR ADJUSTMENTS MADE
FOR LOCAL TERRAIN EFFECTS. AS FOR SENSIBLE WEATHER...MUCH MORE
SEASONABLE WEATHER WILL BE UPON US AS MODERATED ARCTIC HIGH PRESSURE
PUSHES THROUGH THE MIDWEST AND INTO THE OHIO VALLEY. MEANWHILE...THE
BOUNDARY THAT BROUGHT RAIN AND SHOW SHOWERS TO THE FIRST PART OF THE
FORECAST WILL STALL WELL TO THE SOUTHEAST. HOWEVER...A NORTHERN
STREAM WAVE WILL LURE MORE MOISTURE NORTH AHEAD OF ITS SFC
TROUGH...STARTING THURSDAY. THIS RETURN FLOW MOISTURE WILL MAKE THE
FORECAST FOR THE END OF THE WEEK TRICKY...PARTICULARLY IN THE FACE OF
MODEL DISAGREEMENT ALOFT OVER OUR REGION. FOR NOW HAVE GONE WITH A
SMALL CHANCE FOR RAIN OR SNOW STARTING LATE THURSDAY NIGHT AND
CONTINUING THROUGH THE WEEKEND AS DEEP LOW PRESSURE PASSES BY TO THE
NORTH LATE FRIDAY. ANOTHER SYSTEM AND ITS COLD FRONT WILL QUICKLY
APPROACH THE AREA LATER SATURDAY SWINGING THROUGH ON SUNDAY. WITHOUT
THE NORTHERN AND SOUTHERN STREAM PHASING OVERALL PCPN AMOUNTS LOOK TO
BE LIGHT THROUGH THE LATTER PART OF THE FORECAST.
&&
.AVIATION.../06Z TO 06Z/...UPDATED
SURFACE LOW IS MOVING NORTH UP THE LOWER OHIO VALLEY ALONG A SURFACE
BOUNDARY DRAPED ACROSS SOUTHERN ILLINOIS...INDIANA AND OHIO. THE
TRACK OF THE SURFACE LOW WILL KEEP EAST KENTUCKY IN THE WARM SECTOR
WITH VFR CONDITIONS EXPECTED THROUGH AROUND 14Z. MODELS CONTINUE TO
INDICATE A STRENGTHENING LOW LEVEL JET TOWARDS DAWN...ALTHOUGH THEIR
PROJECTIONS MAYBE SLIGHTLY OVERDONE COMPARING THE PROGS WITH
OBSERVED ACARS SOUNDINGS OVER SDF. NEVERTHELESS...EXPECT MARGINAL
LLWS TO BE OBSERVED BY 10Z WITH SPEEDS OF 40 KT AS LOW AS 1500 FT
AGL.
AS THE SURFACE LOW TRACKS OFF TO OUR NORTHEAST...THE LONG AWAITING
COLD FRONTAL PASSAGE WILL FINALLY TAKE PLACE BRINGING A PERIOD OF
SHRA/+SHRA WITH AT LEAST MVFR CIGS AND VSBYS. WOULD EXPECT SOME
BRIEF IFR CONDITIONS AS WELL BUT NOT LONG ENOUGH TO INCLUDE IN TAFS
AT THIS TIME. SOUTHWESTERLY WINDS WILL ALSO INCREASE AS THE FRONT
NEARS WITH GUSTS OVER 20 KT EXPECTED. THE WINDS WILL VEER AROUND
BECOMING WESTERLY AFTER THE FROPA WITH SHRA GRADUALLY DECREASING IN
COVERAGE. PLENTIFUL LOW LEVEL MOISTURE BEHIND THE FRONT SHOULD KEEP
MVFR CIGS AROUND THROUGH THE END OF THE TAF PERIOD.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH THROUGH MONDAY AFTERNOON FOR KYZ044-050>052-058>060-
104-106-108.
&&
$$
SHORT TERM...GREIF/JP
LONG TERM...GREIF
AVIATION...ABE
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
AFDLWX 830 PM EST TUE JAN 16 2007
.SHORT TERM (TONIGHT INTO WEDNESDAY)...
WATER VAPOR LOOP SHOWS A POSITIVELY TILTED UPPER LEVEL TROUGH FROM
THE MIDWEST NORTHEAST THROUGH NEW ENGLAND SHEARING NORTHEAST...WITH
AN UPPER LOW SPINNING OVER THE FOUR CORNERS REGION. ACARS 400-250MB
WIND OBSERVATIONS REVEAL A 160-200KT JET FROM THE PLAINS NORTHEAST
THROUGH NEW ENGLAND. 20Z SURFACE ANALYSIS PLACED A COLD FRONT OFF
THE MID ATLANTIC COAST...WHICH STALLED FROM THE CAROLINA COAST
SOUTHWEST THROUGH NORTH CENTRAL FLORIDA. A 1041MB ANTICYCLONE WAS
SPRAWLED ACROSS THE CENTRAL CONUS.
THE PASSAGE OF THE UPPER LEVEL TROUGH OVERNIGHT WILL DISPLACE THE
MID LEVEL CLOUDINESS TO THE SOUTH. RISING HEIGHTS WILL BE FAVORABLE
FOR THE SURFACE HIGH TO BUILD INTO THE REGION THROUGH TOMORROW. THIS
INCREASE IN ANTICYCLONIC LOW LEVEL SHEAR AND WARM ADVECTION TO THE
WEST WILL END THE LAKE EFFECT SNOW SHOWERS...AND THUS ALLOW
STRATO-CU TO DISSIPATE OVERNIGHT...RESULTING IN A CLEARING SKY.
COLD ADVECTION WILL MAINTAIN DRY ADIABATIC LAPSE RATES
OVERNIGHT...ALLOWING MIXING 25 MPH WIND GUSTS TO THE SURFACE
(SUPPLIED BY THE PRESSURE GRADIENT AHEAD OF THE BUILDING HIGH). WITH
THE PRESSURE GRADIENT LASTING LONGEST EAST OF THE BLUE
RIDGE...TEMPERATURES WILL TEND TO BOTTOM OUT THROUGH THE TEENS
ACROSS THE WESTERN FORECAST AREA.
SURFACE HIGH BUILDS ACROSS THE MID ATLANTIC TOMORROW...FEATURING A
CLEAR SKY. WINDS WILL SLACKEN THROUGH THE DAY AS THEY BECOME
NORTHERLY DURING THE MORNING...THEN LIGHT AND VARIABLE LATE WITH THE
ARRIVAL OF THE HIGH. WENT BELOW MOS GUIDANCE HIGH TEMPERATURES GIVEN
RECENT BIAS...A CLEAR AND CALM START...THE LOSS OF DOWNSLOPE
FLOW...AND THE ARRIVAL OF COLDEST CORE OF AIR ALOFT FROM THIS SYSTEM.
&&
.AVIATION...
COMBINATION OF PRESSURE GRADIENT AND COLD ADVECTION WILL KEEP
NORTHWEST WIND GUSTS OF 25KT THROUGH THE NIGHT. SLACKENING GRADIENT
WILL ALLOW WIND GUSTS TO DIMINISH WEDNESDAY MORNING. PASSAGE OF THE
UPPER LEVEL TROUGH OVERNIGHT WILL CLEAR OUT MID LEVEL MOISTURE...AS
WANING LAKE EFFECT SNOW SHOWERS WILL ALLOW STRATO-CU TO DISSIPATE.
&&
.MARINE...
12Z ETA/MAV MOS AT THOMAS POINT INDICATE 20KT SUSTAINED WINDS
TONIGHT AND BETWEEN 10 AND 15 KNOTS TOMORROW MORNING. 12Z NAM/GFS
PROXIMITY BUFKIT FORECAST SOUNDINGS INDICATE 25-30KT WIND GUSTS
OVERNIGHT...AND 18KT WIND GUSTS TOMORROW MORNING. A SMALL CRAFT
ADVISORY IS IN EFFECT UNTIL NOON WEDNESDAY.
&&
.TIDES...
WATER LEVELS ARE CURRENTLY ABOUT A FOOT BELOW ASTRONOMIC
PREDICTIONS. THE LUNAR CYCLE IS WANING (6% FULL). BLOWOUT
CONDITIONS WILL DIMINISH TOMORROW AFTERNOON.
THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM AND THE NOAA
EXTRATROPICAL STORM SURGE MODEL BOTH SUGGEST CURRENT DEPARTURES
PERSIST OR SLIGHTLY RECOVERS TOMORROW.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 12 PM EST WEDNESDAY FOR
ANZ530>537.
&&
$$
SHORT TERM/AVIATION/MARINE/TIDES...ROGOWSKI
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
AFDMQT 410 PM EST MON JAN 15 2007
.DISCUSSION...
MAIN FCST CONCERNS ARE LES TRENDS TONIGHT INTO TUE AND SNOW/LES
POTENTIAL WITH NEXT MID LVL TROF AND COLD FRONT THU INTO FRI.
WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROF FROM
NRN QUEBEC THROUGH NRN MN AND THE CNTRL PLAINS TO THE SW CONUS AND
RDG FROM THE PAC NW INTO NRN ALBERTA. AN INCREASINGLY SHEARED SHRTWV
WAS SLIDING E THROUGH E UPR MI AND ERN WI. AT THE SFC...BRISK NRLY
WINDS PREVAILED ACRS THE WRN GRT LAKES BTWN LOW PRES OVER NY AND A
RDG FROM NRN ONTARIO INTO THE NRN PLAINS. RADARS INDICATED THAT
LIGHT SNOW SUPPORTED BY 700-300 QVECTOR AHEAD OF THE MID LVL TROF
WAS DIMINISHING BUT VSBYS REMAINED GENERALLY IN THE 2-4SM RANGE FROM
NRN WI INTO SRN UPR MI AT 20Z. MULTIPLE WIND PARALLEL LES BANDS INTO
NRN UPR MI WERE BRINGING OCNLY HEAVY SNOW ESPECIALLY INTO THE HIGHER
TERRAIN. BANDS WERE SHIFTING THOUGH AS WINDS BACK FROM NNE TO N.
PLENTY OF INSTABILITY/MOISTURE AVBL FOR LES AS 17Z KSAW/KCMX TAMDAR
SNDGS INDICATED DEEP MOISTURE OVER THE AREA WITH -19C/-21C AT TOP OF
6K FT INVERSION AND 850 MB TEMPS OF -17C/-20C. UPSTREAM...VERY DRY
ARCTIC AIR WAS FILTERING INTO N AND W LK SUPERIOR WHERE SFC
DEWPOINTS WERE -10F TO -20F. AS A RESULT...LAKE CLOUDS WERE
DEVELOPING CLOSER TO THE SOUTH SHORE OF THE LAKE.
TONIGHT...EXPECT THE REMAINING LIGHT SNOW OVER S UPR MI TO TAPER OFF
TO SCT LIGHT SNOW SHOWERS OR FLURRIES EARLY THIS EVENING...PER RADAR
AND SATELLITE TRENDS. SO...THE SNOW ADVY OVER THE SOUTH WILL BE
DROPPED. GIVEN THE CLOUD TRENDS OVER THE WEST AND UPSTREAM 1000-850
RH IN THE 30-50 PCT RANGE...THE LES SHOULD ALSO DIMINISH THIS
EVENING. SINCE SOME MINOR ACCUMULATIONS OF AN INCH OR TWO ARE STILL
POSSIBLE WILL LEAVE THE WARNING/ADVISORIES INTACT. THE LONGER FETCH
WILL HELP SUSTAIN THE LES INTO N CNTRL AND E UPR MI EVEN WITH THE
DEPARTURE OF THE 850-700 MB MOISTURE. MDLS ARE CONSISTENT WITH THE
GRADUAL BACKING TREND WHICH WILL MOVE THE BEST LOW LVL CONV FROM
MARQUETTE COUNTY TO ALGER/LUCE COUNTIES OVERNIGHT. SINCE LES
INTENSITY IS EXPECTED TO DIMINISH BY LATE THIS EVENING...NO
ADJUSTMENT TO 04Z WARNING/ADVISORY EXPIRATIONS EWAS MADE. ADDITIONAL
ACCUMULATIONS WILL BE GREATEST THIS EVENING IN THE 1-4 INCH RANGE
WITH ONLY 1-2 INCH AMOUNTS...MAINLY E OF MARQUETTE AFT 04Z.
TUE...NW FLOW LES WILL CONTINUE WITH ACCUMULATIONS EXPECTED MAINLY
OVER THE ERN CWA. ALTHOUGH 850 TEMP TEMPS WILL REMAIN NEAR
-20C...THE RELATIVELY SHALLOW COLD AIR(INVERSION HEIGHT NEAR 4K FT)
WILL NOT BE FAVORABLE FOR SNOW GROWTH OR FORMATION OF STRONGER
DOMINANT BANDS. SO...EXPECT AMOUNTS TO REMAIN IN THE 2-4 INCH RANGE
WITH THE GREATEST AMOUNTS BTWN MUNISING AND NEWBERRY. THE SHORTER
FETCH INTO W UPR MI WILL LEAD TO ONLY MINOR ACCUMULATIONS. WINDS
WILL BACK SWRLY TUE NIGHT...PUSHING ANY REMAINING LES OFFSHORE WITH
ONLY MINOR ADDITIONAL ACCUMULATIONS OVER THE FAR NE CWA.
WED...BRISK SW FLOW AND WAA DEVELOPING BTWN THE DEPARTING SFC RDG
AND TROF DEVELOPING OVER THE PLAINS WILL BRING A QUICK WARMUP WITH
TEMPS AOA NORMAL INTO THE MID AND UPPER 20S ALONG WITH PARTLY TO
MOSTLY SUNNY SKIES.
THU INTO FRI...THE GFS TIMING LAGGED THE PREFERRED
UKMET/ECMWF/CANADIAN WITH THE NEXT MID LVL TROF MOVING INTO THE
AREA. ALTHOUGH LITTLE MOISTURE WILL BE AVAILABLE WITH THE SYSTEM AND
THE GFS IS LIKELY A BIT GENEROUS WITH THE QPF...THE TROF
STRENGTH/DYNAMICS JUSTIFY -SN CHANCES ACRS THE CWA. LES WILL RETURN
IN THE WAKE OF THE SYSTEM AS THE ECMWF/GFS SHOW CAA DROPPING 850 MB
TEMPS INTO THE -16C TO -20C BEHIND THE COLD FRONT. NW FLOW FAVORED
AREAS SHOULD SEE BEST CHANCE FOR SIGNIFICANT ACCUMULATIONS ALTHOUGH
THE GFS HINTS AT POSSIBILITY OF WINDS VEERING MORE NRLY FOR A TIME
FRI AS A SECONDARY TROF AND WEAK SHRTWV MOVES THROUGH.
SAT THROUGH MON...GENERALLY FOLLOWING THE HPC PREFERRED 00Z
ECMWF/NCEP ENS MEAN WOULD SHIFT LES FOCUS TO W FLOW FAVORED
LOCATIONS BY SAT WITH LES DIMINISHING SUN AS 850 TEMPS CLIMB ABOVE
-10C. AND WINDS BECOME VARIABLE AND E LATE SUN. UNCERTAINTY
INCREASES SIGNIFICANTLY...PER MDLS AND ENSEMBLES SPREAD...BY MON
WITH POSITION AND STRENGTH OF THE NEXT SIGNIFICANT MID LVL TROF AND
SFC LOW WHICH BRINGS CHANCE OF SNOW ACRS THE CWA.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW ADVISORY UNTIL 11 PM EST THIS EVENING FOR
MIZ001>004-006-084-085.
LAKE EFFECT SNOW WARNING UNTIL 11 PM EST /10 PM CST/ THIS
EVENING FOR MIZ005-009.
&&
$$
JLB
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 340 AM PST MON JAN 15 2007
.SYNOPSIS...A COLD AND DRY AIR MASS WILL REMAIN OVER WESTERN
WASHINGTON TODAY. A PACIFIC FRONTAL SYSTEM WILL PASS THROUGH THE
AREA TUESDAY WITH THE PRECIPITATION AHEAD OF THE SYSTEM BEGINNING
LATE TONIGHT. DRY WEATHER WILL RETURN TO THE AREA WEDNESDAY AND
THURSDAY. ANOTHER WEATHER SYSTEM WILL BRING ANOTHER CHANCE OF
PRECIPITATION TO THE AREA FRIDAY AND SATURDAY.
&&
.SHORT TERM...VERY TRICKY FORECAST THIS MORNING REGARDING THE
PRECIPITATION AMOUNT AND TYPE FOR TUESDAY MORNING. FOR
TODAY...SATELLITE IMAGERY SHOWS UPPER LEVEL RIDGE MOVING EASTWARD
WITH THE RIDGE AXIS ALONG THE COAST AT 10Z. FRONT THAT WILL BE THE
WEATHER PRODUCER ALSO MOVING EASTWARD THIS MORNING AND IS NEAR 135W
AT 10Z. SURFACE HIGH PRESSURE REMAINS OVER EASTERN WASHINGTON WITH
FLAT SURFACE GRADIENTS. AMS ALOFT SHOWING SIGNS OF WARMING UP WITH
MOST HIGH MOUNTAIN LOCATIONS...LIKE PARADISE...ABOUT 10 DEGREES
WARMER THAN LAST NIGHT. STRONG LOW LEVEL INVERSION STILL IN PLACE
OVER WESTERN WASHINGTON WITH ACARS SOUNDINGS SHOWING THE TOP OF
INVERSION NEAR 5500 FEET. MOSTLY SUNNY SKIES TODAY FOR THE CWA WITH
JUST SOME HIGH CLOUDS MOVING THROUGH THE REGION. CLOUDS INCREASE
TONIGHT WITH RAIN DEVELOPING ALONG THE COAST AND PRECIPITATION
SPREADING INLAND AFTER MIDNIGHT. FRONT CURRENTLY TIMED TO REACH THE
COAST MID MORNING AND BE THROUGH THE SEATTLE AREA LATE
MORNING/MIDDAY. NOW FOR THE PRECIPITATION TYPE. THE
VARIABLES...SURFACE GRADIENTS...LIGHT SOUTHEASTERLY...IF THEY WERE
STRONGER THE GRADIENTS COULD HELP WARM AND DRY OUT THE LOWER LAYER
OF THE AMS OVER PUGET SOUND. TEMPERATURES...WITH THE INCREASING
CLOUD COVER OVERNIGHT MINIMUM TEMPERATURES WILL BE WARMER THAN THE
LAST FEW NIGHTS BUT STILL BELOW FREEZING BY A COUPLE OF DEGREES OVER
THE INTERIOR. TEMPERATURES RIGHT AHEAD OF THE FRONT WILL BE NEAR
FREEZING OVER THE PUGET SOUND INTERIOR AT THE SURFACE. TEMPERATURES
ALOFT WILL WARM UP OVERNIGHT WITH THE 850 MB TEMPERATURES AROUND -2C
RIGHT AHEAD OF THE FRONT. THICKNESS VALUES...1000 TO 850 MB
THICKNESS VALUES BELOW 1300M FROM SEATTLE NORTHWARD. WINDS
ALOFT...WINDS IN THE 1000-850 MB LAYER GENERALLY SOUTHWESTERLY 5 TO
15 KNOTS. GIVEN THESE VARIABLES HERE IS THE GAME PLAN. WITH THE
PRECIPITATION ARRIVING IN THE INTERIOR BETWEEN 09Z-12Z AND
TEMPERATURES NEAR FREEZING AND THE LOW 1000-850 THICKNESS VALUES
PRECIPITATION WILL START OFF AS SNOW. AS THE MORNING WEARS ON AND
THE TEMPERATURES WARM WITH THE INCREASE IN THE LOW LEVEL ONSHORE
FLOW IN MOST PLACES THE PRECIPITATION WILL CHANGE OVER TO RAIN.
CURRENT QPF VALUES ASSOCIATED WITH THE FRONT RANGE FROM .10 TO .30
INCHES SO EVEN IF THE PRECIPITATION REMAINS IN THE FORM OF SNOW THE
MAXIMUM SNOW AMOUNTS LOOK TO BE 3 OR 4 INCHES. THE PLACES WHERE THE
PRECIPITATION IS MOST LIKELY TO REMAIN AS SNOW WILL BE OVER THE HOOD
CANAL AREAS WHERE THE SOUTHEASTERLY GRADIENTS COULD TRAP THE COLD
AIR AND FROM NORTH OF SEATTLE TO CANADIAN BORDER GENERALLY EAST OF
I-5. BEHIND THE FRONT...NOT MUCH IN THE WAY OF SHOWER ACTIVITY AND
WITH THE WEAK ONSHORE GRADIENTS IF A CONVERGENCE ZONE FORMS IT WILL
LIKELY REMAIN NEAR THE EAST ENTRANCE TO THE STRAIT. DRYING
NORTHWESTERLY FLOW ALOFT FOR WEDNESDAY WITH SURFACE HIGH PRESSURE
BUILDING OVER THE AREA.
.LONG TERM...EXTENDED MODELS SIMILAR ON THURSDAY WITH FLAT UPPER
LEVEL RIDGE OVER THE AREA AND SURFACE HIGH PRESSURE. MODELS DIVERGE
ON FRIDAY AND SATURDAY WITH THE EURO AND CANADIAN STAYING WITH THE
IDEA OF A WEAK SYSTEM TRYING TO MOVE INTO THE AREA WHILE THE GFS
CHANGES ITS TUNE AND NOW INDICATES A BLOCKING UPPER LEVEL PATTERN
DEVELOPING OVER THE WEST COAST. WITH THE GFS NOT SHOWING MUCH RUN TO
RUN CONSISTENCY WILL STAY WITH THE CANADIAN/EURO SOLUTION AND KEEP
CHANCE OF RAIN IN THE FORECAST FOR FRIDAY AND SATURDAY. FELTON
&&
.AVIATION...INCREASING CIRRUS TODAY AND MID LEVEL CLOUDS THIS
EVENING...MID LEVEL OVERCAST LOWERING TONIGHT WITH PRECIP DVLPG
AFTER MIDNIGHT. LIGHT AND VARIABLE OR LIGHT EAST WIND BECOMING
SE10KTS THIS EVENING FOR KSEA. WITH SNOW OR RAIN ABOUT 24 HOURS AWAY
FOR KSEA WILL SIMPLY INDICATE A MIX TOWARD THE END OF THE TAF PERIOD
AS A HEADS UP FOR EARLY TUE MORNING. MM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
.SMALL CRAFT ADVISORY COASTAL WATERS...WEST ENTRANCE STRAIT.
.AIR STAGNATION ADVISORY INTERIOR LOWLANDS THROUGH TUE MORNING.
$$
WEATHER.GOV/SEATTLE.