Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
251 AM EST Thu Dec 08 2016

Valid 12Z Thu Dec 08 2016 - 12Z Sat Dec 10 2016

...Heavy snow and rain possible over the Sierras...

...Heavy snow possible in favored areas downwind from the Great
Lakes...

...Areas of rain and freezing rain possible over interior portions
of the Pacific Northwest...

...Temperatures will be 15 to 35 degrees below average over the
Rockies and High Plains...

A front off the West Coast will move onshore overnight Thursday
moving into the Pacific Northwest, Great Basin, and Central
California by Friday evening.  The storm will produce rain and
higher elevation snow over Northern/Central California that will
expand into parts of the Great Basin and the Pacific Northwest on
Thursday.  Overnight Thursday, the snow will expand into parts of
the Northern/Central Rockies into Friday evening.  The snow levels
will rise over California overnight Thursday as well.  In
addition, there will be pockets of rain/freezing rain over some of
the interior portions of the Pacific Northwest. 

Meanwhile, upper-level energy and favorable upper-level flow will
aid in producing lake effect snow downwind from the Great Lakes
into parts of Northern New England through Friday evening. 
Additionally, upper-level energy moving over the Western and
Central Gulf Coast States will aid in producing rain over parts of
the Southern Plains and the Lower Mississippi Valley through
Friday morning.  Rain and embedded thunderstorms will also develop
over the southern portion of Florida through Friday evening.


Ziegenfelder


Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 AM EST THU DEC 08 2016

VALID 12Z SUN DEC 11 2016 - 12Z THU DEC 15 2016

...ARCTIC AIR TO SURGE INTO THE LOWER 48 NEXT WEEK...


...PATTERN OVERVIEW...

A MIDDLE/UPPER-TROPOSPHERIC CLOSED LOW REMAINS FORECAST TO DROP
SOUTHWARD FROM NUNAVUT THIS WEEKEND AND THEN TURN EASTWARD THROUGH
SOUTHERN CANADA DURING THE MIDDLE OF THE NEXT WEEK.
UNDERNEATH...UNCERTAIN NORTHERN PACIFIC SHORTWAVE ENERGIES
PROGRESS FROM THE NWRN US/CA THROUGH THE INTERMOUNTAIN W/ROCKIES
SUN INTO MON IN GENERAL LOWER 48 ZONAL FLOW LEADING TO SOME
CENTRAL US AMPLIFICATION AHEAD OF THE NRN STREAM CANADIAN UPPER
LOW. A BROAD CYCLONIC CIRCULATION WITH UNCERTAIN NRN STREAM
INFLUENCE ALOFT SHOULD THEN ENCOMPASS THE EASTERN HALF OF THE
LOWER 48 INTO NEXT WED/THU AS ADDITIONAL PACIFIC IMPULSES WORK
BACK TO THE WRN STATES.

...GUIDANCE PREFERENCES...

GUIDANCE QUESTIONS ARISE WITH HOW PACIFIC SHORTWAVES ZIP THROUGH
THE FLOW ACROSS THE CONUS NEXT SUN-MON AHEAD OF THE INTENSE COLD
SURGE FROM THE NORTH. BIGGER QUESTIONS INTO MIDWEEK CONCERN THE
EXTENT OF NRN STREAM HEIGHT FALLS WORKING INTO THE NWRN US ALONG
WITH POTENTIALLY MORE ERNEST NRN AND SRN STREAM TROUGH HEIGHT
FALLS/PHASING DOWNSTREAM OVER THE E-CENTRAL US. GUIDANCE HAS NOT
BEEN VERY CONSISTENT WITH EMBEDDED IMPULSE TIMING/SFC DEFINITION
OUT FROM SHORT RANGE TIME SCALES INTO EARLY NEXT WEEK LENDING A
COMPOSITE SOLUTION. HOWEVER...CAN THE ARCTIC SURGE SPIN UP
DEEPENING LOW PRESSURE ALONG THIS LEADING FRONT TO SLOW ITS
PROGRESSION EASTWARD NEXT TUE/WED AS CHAMPIONED BY RECENT GFS
RUNS? WPC PROGS DO NOT EMPHASIZE THIS HEAVIER RAIN AND NORTHWARD
WINTER WEATHER THREAT AT THIS POINT...BUT IT REMAINS POSSIBLE
CONSIDERING NRN STREAM AMPLITUDE EXTENDING THROUGH ALASKA.


...WEATHER HIGHLIGHTS/THREATS...

PERSISTENT WEST TO EAST MID-LEVEL FLOW WILL KEEP THE WESTERN
REGION ACTIVE, ESPECIALLY OVER NORTHERN CALIFORNIA NORTHWARD ALONG
THE COASTAL RANGE AND CASCADES. ADDITIONAL UPLIFT VIA THE ARCTIC
BOUNDARY MOVING OUT OF MONTANA WILL PROVIDE ANOTHER MECHANISM FOR
SNOWFALL OVER THE BITTERROOTS AND SAWTOOTH RANGE AND BROAD
VICINITY. GENERALLY ABOVE AVERAGE TEMPERATURES WILL CONTINUE FOR
THE SOUTHWESTERN FIFTH OF THE CONUS (CA/NV/UT/AZ AND WESTERN
CO/NM).

WITH THE FORECAST ARCTIC SURGE COMING OUT OF SOUTHWEST CANADA INTO
THE N-CENTRAL US...AN IMPRESSIVE AREA OF WELL BELOW AVERAGE
TEMPERATURES WILL RUSH SOUTHWARD AND EASTWARD FROM THE NORTHERN
HIGH PLAINS THROUGH THE MIDWEST AND EVENTUALLY TO THE EAST COAST
BY WED/THU NEXT WEEK. TEMPERATURES MAY BE 20-30 DEGREES BELOW
AVERAGE AND MAY FLIRT WITH SOME RECORDS (PERHAPS RECORD LOW
MAXIMA) THOUGH THE LONGER PERIOD STATIONS GENERALLY HAVE SOME VERY
COLD RECORDS BY NOW (MID-DECEMBER).

NW FLOW AND COLD AIR OVER THE GREAT LAKES SHOULD SUPPORT A
MULTI-DAY LAKE EFFECT EVENT FROM MICHIGAN EASTWARD THROUGH NE
OHIO/NW PA INTO WESTERN/CENTRAL NY INCLUDING THE TUG HILL PLATEAU.
TRACK OF THE EXITING SFC LOW AND INCOMING SFC HIGH WILL DETERMINE
WHO SEES THE MOST SNOW...BUT SETUP LOOKS GOOD PROVIDED ENOUGH
MOISTURE CAN BE WRUNG OUT IN THE OVERALL DRY/COLD AIRMASS. GLOBAL
MODELS/ENSEMBLES GENERALLY HAVE A GREEN LIGHT FOR AT LEAST
LIGHT-MODERATE SNOW NEXT TUE-THU (AND PERHAPS BEYOND).


SCHICHTEL

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
321 AM EST THU DEC 08 2016


FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION
VALID DEC 08/1200 UTC THRU DEC 11/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1 UPDATE...

NO SIGNIFICANT CHANGES WERE MADE TO THE PRELIM DAY 1...JUST MINOR
ADJUSTMENTS BASED IN LARGE PART ON THE 00 UTC SSEO MEAN.

DAY 1...

...PACIFIC NORTHWEST/CALIFORNIA TO THE NORTHERN ROCKIES... 
 
A LOW-AMPLITUDE SHORTWAVE RIDGE CENTERED ALONG THE PACIFIC
NORTHWEST/NORTHERN CA COASTS EARLY THU IS EXPECTED TO SHIFT EAST
INTO THE INTERMOUNTAIN WEST BY EARLY FRI...GIVING WAY TO AN
APPROACHING SHORTWAVE TROUGH...WITH A MID LEVEL CENTER CLOSING OFF
WEST OF VANCOUVER ISLAND.  WARM ADVECTION PRECIPITATION CENTERED
ACROSS NORTHERN CA THU MORNING IS FORECAST TO LIFT NORTH AND EAST
AHEAD OF THE APPROACHING SYSTEM...WITH LIGHT TO MODERATE AMOUNTS
SPREADING INTO THE NORTHERN INTERMOUNTAIN WEST/ROCKIES. 
INCREASING ONSHORE FLOW/UPPER FORCING AHEAD OF THE APPROACHING LOW
WILL AFFORD AN INCREASE IN COVERAGE/AMOUNTS ACROSS WESTERN
ORE/SOUTHWESTERN WA LATE THU INTO FRI...WITH LOCALLY HEAVY AMOUNTS
POSSIBLE ALONG THE FAVORED TERRAIN.  AS WARM MOIST AIR FROM THE
PACIFIC MOVES ACROSS THE TOP OF DRY LOW LEVEL COLD AIR SUPPORTED
BY EASTERLY FLOW...THIS SYSTEM IS EXPECTED TO PRODUCE A VARIETY OF
PRECIPITATION TYPES ACROSS WESTERN WA/ORE...INCLUDING
SLEET/FREEZING RAIN ACROSS THE VALLEYS AND LOWLANDS OF REGION. 
HEAVY SNOWS WILL BE POSSIBLE IN HIER ELEVATIONS OF THE CASCADES. 
REFER TO THE WINTER WEATHER SUITE OF PRODUCTS FOR FURTHER DETAILS
ON THE POTENTIAL HEAVY SNOW AND ACCUMULATING ICE ACROSS THIS
REGION.
 
FURTHER TO THE SOUTH...A PLUME OF RELATIVELY ANOMALOUS MOISTURE
EXTENDING FROM THE PACIFIC INTO CENTRAL CA INTERACTING WITH ENERGY
ALOFT IS EXPECTED TO FUEL PERIODS OF LIGHT TO MODERATE
PRECIPITATION ALONG THE CENTRAL CA COASTAL RANGES INTO THE
INTERIOR VALLEYS AND SIERRA.

WITH THE GUIDANCE IN OVERALL GOOD AGREEMENT WPC QPF ACROSS MOST
AREAS FOLLOWED A BLEND OF THE GFS/ECMWF AND AN ENSEMBLE OF THE
HI-RES GUIDANCE...INCLUDING THE HRW-ARW/NMMB AND THE NSSL-WRF. 
 
...GREAT LAKES... 
 
STRONG COLD AIR ADVECTION AND DEEP CYCLONIC FLOW IN THE WAKE OF A
LOW MOVING ACROSS SOUTHERN QUE INTO ATLANTIC CANADA WILL SUPPORT
LAKE EFFECT ACTIVITY WITH LOCALLY HEAVY ACCUMULATIONS POSSIBLE IN
THE LEE OF THE GREAT LAKES.  HEAVY ACCUMULATIONS ARE LIKELY IN LEE
OF THE LOWER LAKES AS SOUTHWESTERLY-WESTERLY FLOW PROMOTES SINGLE
BAND SNOWS INTO NORTHEAST PA/WESTERN NY AND THE TUG HILL REGION OF
NY.  REFER TO THE WPC WINTER WEATHER SUITE OF PRODUCTS FOR FURTHER
DETAILS.


DAYS 2 AND 3...

...PACIFIC NORTHWEST/CALIFORNIA/GREAT BASIN/INTERMOUNTAIN
WEST/NORTHERN TO CENTRAL ROCKIES...

THE PERSISTENT UPPER TROUGH ACROSS THE NORTHEAST PACIFIC IS
FORECAST TO HAVE PERTURBATIONS ROTATING AROUND IT WITH A FEW
DEFINED LOW PRESSURE SYSTEMS COMING INTO VANCOUVER ISLAND THAT
WILL ENHANCE PRECIPITATION IN THE PACIFIC NORTHWEST. FURTHER
SOUTHERN...ON DAY 2 THE GFS FCST SHOWS THE STRONGEST 700 MB JET
COMING ONSHORE FROM THE PACIFIC INTO NORTHWEST CA.  THE STRONGEST
MOISTURE FLUXES COME INTO NORTHERN CA AND NV SO THE LATTER HALF OF
DAY 2 THROUGH DAY 3 WILL SEE EXTENSIVE PRECIPITATION ACROSS THE
RANGES OF NORTHERN CA...SPREADING INTO THE RANGES OF NORTHERN NV
AND UT AS THE MOISTURE FLUXES PERSIST FOR AN EXTENDED PERIOD.

OROGRAPHIC FORCING ENHANCES RESPONSES TO THE FLOW ACROSS THE WA/OR
CASCADES AS WELL AS THE NORTHERN ROCKIES THROUGH THE PERIOD.  LIFT
IN WESTERN MT TO NORTHERN ID AND NORTHEAST WA IS AIDED BY LOW-MID
LEVEL FRONTOGENESIS. 

MANUAL WPC LIQUID EQUIVALENTS ARE CLOSE TO THE
MULTI-MODEL/ENSEMBLE MEAN CONSENSUS THROUGH THE FORECAST...WHICH
SLIGHTLY INCREASED PRIOR FORECASTS. THIS IS PARTLY DUE TO THE
PERSISTENCE OF MULTIPLE UPPER JET MAXIMA AN ASSOCIATED UPPER
DIVERGENCE THAT STREAM ONSHORE AND WEST TO EAST ACROSS THE PACIFIC
NORTHWEST INTO THE NORTHERN ROCKIES AND A SEPARATE MAXIMA CROSSING
NORTHERN CA/NV/UT/WY.
ONCE THE MAXIMA REACH AND PERSIST OVER WY...SNOW IN UT EXTENDS
INTO THE RANGES OF NORTHERN CO...WITH HIGH AMOUNTS IN NORTHERN CO
THAN SOUTHERN DUE TO CLOSER PROXIMITY TO THE UPPER JET IN WY
ACROSS NORTHERN CO.


...NORTHERN TO CENTRAL PLAINS/UPPER MS VALLEY/UPPER GREAT LAKES
DAY 3...

THE MODELS DIFFER ON THE AMPLITUDE AND STRENGTH OF AN 850-700 MB
WAVE AND ATTENDANT SURFACE LOW PRESSURE...FLANKED ON THE WEAK END
BY THE ECMWF AND ON THE STRONG END WITH THE STRONGER NAM
SOLUTION...WHICH ALSO PRODUCES PRECIP FURTHER NORTH THAN OTHER
SOLUTIONS.  MANUAL PROGS USED THE 00Z GFS/UKMET AND 18Z-0Z GEFS
MEAN AS A MIDDLE OF THE ROAD APPROACH TO THE AMOUNTS AND TIMING OF
PRECIP...MINUS THE END OF DAY 3...WHEN THE UKMET KEEPS PRECIP
GOING IN NORTHWEST IA/SOUTHWEST MN IN RESPONSE TO LOW PRESSURE
DEVELOPING FURTHER SOUTHWEST IN THE CENTRAL PLAINS.  MORE
WEIGHTING WAS GIVEN TO THE 12Z UKMET/00Z ECMWF INSTEAD WITH LOW
CONFIDENCE ON THE CHANGE ON THE 00Z UKMET RUN (AT LEAST UNTIL
BETTER RUN TO RUN CONTINUITY DEVELOPS AND SUPPORT FROM OTHER
MODELS DEVELOPS) .  STRONG 850-700 MB THETA-E ADVECTION AND
CONVERGENCE DRIVE THE STRIPE OF PRECIP...IN CONJUNCTION WITH 300
MB DIVERGENCE MAXIMA IN A WEAKLY COUPLED UPPER JET PATTERN.  SEE
THE WINTER WEATHER PROGS AND DISCUSSION FOR DETAILS ON THE
RESULTANT WINTER ACCUMULATIONS/PROBABILITIES.


...GREAT LAKES DAY 2 INTO EARLY DAY 3...

COLD AIR ADVECTION AND NORTHWESTERLY FLOW IN THE GREAT LAKES EARLY
ON DAY 2 GRADUALLY GIVES WAY TO WEAKENING AND BACKING FLOW IN THE
DIRECTION OF A MORE WESTERLY FLOW IN THE UPPER LAKES BY FRI
MORNING.  PERSISTENT NEAR SHORE CONVERGENCE AND LOW LEVEL ASCENT
MAXIMA SPUR LAKE EFFECT SNOW MAXIMA NEAR THE EASTERN SHORE OF LK
SUPERIOR...IN NORTHWEST LOWER MI DOWNSTREAM FROM TRAVERSE
BAY...SOUTHWEST LOWER MI DOWNSTREAM OF THE WIDE CROSS LK MI
TRAJECTORIES...DOWNSTREAM FROM LK ERIE WHERE CROSS LAKE HURON AND
LK ERIE TRAJECTORIES PERSIST...AND FINALLY NEAR THE SOUTHEAST
SHORE OF LK ONTARIO.
MANUAL PROGS USED AMOUNTS CLOSER TO THE HIGHER RES NAM AND
PARALLEL CONUS NESTED NAM DUE TO FAVORABLE HIGH LAPSE RATES DUE TO
THE COMBINED WARM WATER AND COLD TEMPS ALOFT.

ON DAY 3...ACTIVITY DIMINISHES AS DRIER AIR ALOFT MOVES IN FROM
THE UPPER MS VALLEY EARLY IN THE PERIOD...THEN CROSSING FURTHER
DOWNSTREAM ACROSS LAKE ERIE AND THEN ONTARIO. 
THE BRIEF RESPITE DOESN'T LAST LONG AS LARGER SCALE MOISTURE
ADVECTION OCCURS FROM THE SYSTEM MOVING FROM THE PLAINS ACROSS THE
UPPER MS VALLEY AS DESCRIBED ABOVE.

REFER TO THE WPC WINTER WEATHER SUITE OF PRODUCTS FOR FURTHER
DETAILS.

GRAPHICS AVAILABLE ON THE WEB AT
WWW.WPC.NCEP.NOAA.GOV/QPF/QPF2.SHTML

PEREIRA/PETERSEN

24HR QP VT 09/12Z
 0.01 497294 499285 501277 500262 499250 499242 500234 501226
      498221 497217 497212 498203 499200 497192 495189 490187
      486188 482185 479170 479144 474121 470109 469106 468100
      466095 461086 456081 452078 445073 443070 441072 444076
      448080 451083 452086 448092 444093 438092 435090 431091
      426088 424087 422089 422091 425097 426100 424101 420102
      417105 413103 406095 403098 401104 395105 393109 385114
      381117 378121 375125 376130 384127 389128 393127 397129
      402131 408132 414132 416132 415135 411139 402141 397140
      393141 384145 384148 388151 391153 391156 392161 388166
      385172 385175 388177 392179 395180 397182 398187 399193
      397196 395196 390194 386191 381188 377184 374181 369180
      359179 354180 350182 349187 353190 358192 362195 362197
      363201 361202 355201 346195 345193 343194 341197 341208
      344218 344224 346230 349237 353240 356239 362241 366240
      369240 371243 369258 371263 375263 383260 389255 392254
      394256 398260 407263 413263 418263 429267 439270 439285
      443292 450300 456307 467311 475304 478299 482301 491302
      494301 495299 497294
 0.01 492661 492656 490656 486655 480668 477679 472690 471693
      468694 460695 457693 454695 452696 451700 448707 444709
      440713 439719 437724 431728 430730 432731 438732 441734
      440737 438740 436741 429747 427755 425756 422754 421761
      415771 414778 411783 410786 407787 402790 396791 389794
      384797 383801 383804 389801 393801 395803 399800 402797
      405799 408805 410811 411821 413826 417828 419823 422818
      424816 426817 431823 438831 441833 443835 443839 439845
      438847 435848 425843 421843 419841 416837 413833 408831
      410840 412857 413863 417867 421870 427871 431871 439871
      448871 453873 456880 455889 451901 450908 449910 448913
      447911 445913 445919 446921 450920 451925 459932 462939
      464945 466952 467957 467962 468967 471967 474964 478967
      481967 482965 486962 489956 491950 491947 489944 489941
      485911 483899 480899 478901 477907 474915 471915 471909
      475897 478891 482887 484885 488885 487883 483878 483872
      481865 479861 475853 472849 465839 463832 463824 465809
      466801 465794 462788 457783 454784 451782 448780 445785
      442792 439785 438780 439777 441770 446759 452751 455745
      454738 453731 457726 461723 464719 476715 479714 475711
      479701 485687 488681 490675 492668 492661
 0.01 460639 457632 454628 451628 449630 445635 442641 439646
      435650 432652 430654 426659 423664 422670 423679 426684
      430687 434689 439685 441679 444672 451662 455658 458652
      459647 460639
 0.01 424065 425060 423055 424048 420048 416055 412056 408054
      404053 401055 396059 384070 377073 376076 375082 376087
      376092 376098 379099 379091 379085 384083 388082 392083
      394092 396094 396089 397080 400078 405078 408080 412080
      415072 417069 421066 424065
 0.01 388758 387751 385749 383750 376753 369752 365753 364755
      364760 365764 366766 371770 376770 383768 386763 388758
 0.01 231975 236988 238993 242998 251006 261015 266018 269019
      273020 278022 286023 298027 306039 310044 312047 315048
      322049 326047 319037 319031 321025 323018 325013 326003
      323989 323980 323976 322973 322961 323954 323949 322946
      320943 318944 316948 314955 310990 311997 310008 309014
      308018 304019 300018 298016 293012 284001 282994 281991
      282986 284980 288976 292971 295966 301954 307939 307931
      307923 306914 304908 302901 298893 295888 291883 286884
      283885 282888 280894 278897 276895 273892 270891 263890
      257891 253892 250894 245897 242901 238907 238914 235931
      233938 230944
 0.01 281794 280784 277777 272762 266748 263741 256741 252747
      250753 247768 245776 243781 236793 232806 230812 229820
      230825 231828 235833 237834 239833 243825 248814 250812
      253813 255815 256820 254826 254835 256842 258850 260853
      264855 265856 269856 278846 281838 282831 281823 280815
      279808 280804 280797 281794
 0.25 484268 485256 485245 481232 477227 474224 476220 483218
      486217 487214 483209 479207 476207 471205 465204 460200
      456195 455192 456187 458181 458176 454169 453159 451153
      447148 442144 435142 426143 424146 425148 430154 433161
      434167 433170 434174 434179 432183 431186 434188 439204
      435210 432210 428209 422207 419214 415210 410209 404207
      396201 373186 365183 359183 355183 353185 355187 360189
      366192 371199 378208 381215 378217 374214 366210 361208
      354205 349204 348210 350217 353223 357225 360226 369228
      379231 401247 430250 445250 452251 458254 463256 466256
      469257 473267 477273 484268
 0.25 474882 473876 472872 470863 468859 465857 462859 460863
      461871 463881 465890 463898 463903 465905 467903 468893
      471887 474882
 0.25 455859 455856 454852 452850 449850 448851 444853 443854
      441856 439858 440861 443863 445864 448864 452863 453862
      455859
 0.25 449811 449807 447805 443805 440808 438809 435811 434814
      433816 434819 436821 439821 442821 446819 447817 448814
      449811
 0.25 444749 443747 439747 436746 434749 433752 432756 433761
      433766 434770 436770 438768 439765 439762 441758 442755
      443752 444749
 0.25 443108 439104 436103 433104 431108 430109 426108 423110
      422112 420114 417115 411113 408107 407105 405106 404108
      398110 393112 389116 401121 407122 414123 420123 423124
      425120 427115 433112 438111 441110 443108
 0.25 421228 421227 420226 420224 418223 418222 418223 416225
      416227 417228 419229 421229 421228
 0.25 428788 427784 422783 419787 418792 417797 417802 416809
      418814 420811 422806 424801 425798 427793 428788
 0.25 419161 421157 420152 419150 415149 412149 408149 406149
      404151 403155 404159 406161 408162 412163 413165 415165
      417163 419161
 0.25 428862 428860 427859 427857 425856 425855 424854 423853
      422852 420851 419853 419856 420858 420859 421860 422862
      424864 426864 428862 428862
 0.25 396219 395219 394219 393218 392218 390219 388219 388217
      387216 385216 385219 386220 388220 390221 391222 393222
      394221 395221 396219
 0.25 283952 281946 279943 275940 272935 268925 264917 259907
      257905 253908 248917 247922 246929 246935 244939 237947
      233955 232960 232965 234971 237974 244981 246987 248990
      252994 257995 261992 261987 260981 263977 271972 277966
      281959 283952
 0.25 272799 272792 270787 267783 264780 255777 251779 249784
      244793 241802 239806 239813 242814 243812 245808 249805
      252804 255806 259808 264809 271804 272799
 0.50 477240 478238 478235 477235 476234 474233 473233 471233
      471235 470235 470237 470238 472240 473241 475242 477241
      477240
 0.50 467240 467235 466233 462228 466224 469218 468214 465212
      460208 456205 452205 451207 447211 442213 431216 428219
      426222 427225 436233 434239 436242 440243 451241 457243
      460243 463241 467240
 0.50 429245 431242 429239 426237 421234 415232 413231 413227
      415221 415218 413215 407214 393200 386195 376190 367187
      361185 355184 360188 363188 365187 368189 370193 383207
      390213 399219 404221 405227 401230 397231 396235 397237
      399241 403243 408243 419246 424247 429245 429245
 0.50 441154 441153 440151 438150 437151 437153 437155 439156
      441155 441154
 0.50 439758 439755 439753 438751 436751 435753 435754 435756
      435758 435761 436762 436763 438764 438763 438760 439758
      439758
 0.50 425791 425789 424789 423788 422789 421791 421792 420794
      420796 419797 419799 419801 420803 421801 422800 422799
      423797 424796 425794 425793 425791
 0.50 408119 409117 408116 407114 406114 405112 403112 401112
      399113 398115 399116 401117 403118 404118 404119 406119
      408119 408119
 0.50 375225 375221 372216 370215 368216 365215 362212 358210
      353209 354215 355219 360221 365223 369225 374226 375225
 0.50 276960 275954 272947 269943 267937 262927 257924 255925
      254929 252935 250940 247945 243949 239951 235955 233961
      235967 239971 244972 251973 257971 268967 273964 276960
 0.50 269798 269794 267790 263787 258786 254786 252788 249792
      246798 248801 253800 257803 261805 265802 269798
 1.00 461223 461217 456215 451215 447215 444216 440218 437221
      437224 439225 444226 448225 451222 455222 460223 461223
 1.00 425242 424240 423239 421238 419237 418237 416237 416239
      417240 419241 420242 422243 424243 425242
 1.00 411223 412221 412219 412218 410217 408218 408220 408222
      409225 411224 411223
 1.00 402216 400211 398208 395205 391202 387199 384197 379197
      382200 385204 388208 391211 394214 398216 402216
 1.00 364218 363217 362215 362214 360213 358213 358214 358215
      359217 361219 363219 364218
 1.00 260962 260956 257952 254951 250953 246954 243956 239959
      241965 243968 248969 254968 257966 259963 260962
 1.50 448221 447219 445219 443219 441220 443222 445223 446223
      448221
 1.50 400213 399211 398210 397208 395206 394205 393205 392204
      390203 389204 390206 392208 392209 393210 395212 396213
      398214 400213
 2.00 397210 395208 395207 394207 393207 393208 394209 395210
      397211 397210 

24HR QP VT 10/12Z
 0.01 516259 518246 519241 518237 518220 516206 512189 510184
      507180 500172 498167 497161 495155 495146 492111 489092
      487078 481053 472033 458010 451000 447999 445997 439997
      436995 431994 428994 427996 425002 423009 426014 432023
      439034 437037 434037 436043 439045 441038 451049 455060
      453067 453070 451072 447072 445070 442067 439068 438071
      445075 448080 450083 449088 445090 435089 431088 429086
      425085 422086 420088 420092 420097 419101 415104 412101
      409097 404097 403103 397102 395102 394105 395108 391111
      387116 388123 392124 397128 406136 407141 406145 402148
      399153 397158 399164 401170 401178 401188 396191 393192
      389191 383189 374182 368179 362181 359184 358187 361190
      365197 364200 362201 359202 356200 349194 343190 341190
      342194 344200 344207 341213 341219 345234 350242 353246
      355251 357263 363270 366270 368272 372278 377279 380278
      384279 391271 395266 397264 401264 405267 411269 417271
      423271 434274 442279 451292 458301 462307 468306 473305
      477302 486301 494298 502294 509286 516259
 0.01 486864 487861 486859 485857 482854 477848 473842 466838
      461832 457825 454808 448798 444793 440789 438784 437781
      437775 437766 438761 439758 440754 443752 447746 446738
      447733 452727 459722 465715 468714 470711 471706 469701
      467699 462700 460699 446708 442712 440716 439725 436727
      435731 438733 438737 434743 433745 431747 429745 426742
      422740 419743 418747 417752 417757 417763 413767 410773
      408780 396788 389793 383799 381802 381805 383806 386807
      389804 394801 400800 405804 406810 407815 408823 409827
      412830 414833 421832 424828 429826 431825 434828 436837
      438840 439846 436853 431852 428849 424842 423836 419837
      414840 411838 409838 409843 410846 415863 417868 421870
      429871 436871 445870 452868 456867 459869 461873 462878
      459886 458892 459897 460901 462905 467912 469912 471907
      477892 481886 483879 484874 484869 486864
 0.01 426063 426058 425051 424047 422046 420048 420053 421059
      419064 416061 411059 404057 398056 395057 389061 385064
      382065 379068 377071 374080 375082 379083 382083 384086
      385090 385093 387091 391087 394091 398088 400083 402080
      411081 416088 420083 424065 426063
 0.01 290795 289787 282784 276782 272780 263770 255762 250763
      248766 245772 242783 233793 226802 222817 222824 223829
      227837 229839 232838 235834 238828 243823 248820 251814
      254810 262807 261815 259820 259824 258828 260832 264833
      266835 271834 273831 273826 272816 277811 280809 285805
      287801 290795
 0.01 231973 239979 252979 261979 272976 279972 278968 276964
      268959 266961 263961 259959 252953 241951 237953 234957
      231961
 0.25 499282 501277 502272 502265 502251 501223 499214 495206
      487201 482199 477199 467202 459200 457198 457195 459189
      461185 464181 466178 470176 477174 480170 483167 484162
      484157 480145 477134 472131 467130 461128 455131 449137
      445135 442132 440129 440122 443117 448115 450110 452105
      453102 450097 439095 434094 431092 426090 426095 427101
      423103 418109 412108 409105 407104 405105 402108 398109
      396115 399120 403123 415133 415140 414145 408150 406152
      405156 407160 411170 413174 416177 425176 439170 442171
      442173 440179 438183 439188 442193 447196 450200 450204
      449206 445208 441210 437211 431211 426210 424207 423202
      421199 417198 413199 410202 406205 386194 378189 372188
      369191 377209 375212 370213 363215 361218 362221 365225
      371232 378238 387245 394249 404253 420253 432255 441254
      451254 456254 461257 466262 470271 471275 474279 479280
      482280 489281 494283 499282
 0.25 470895 470893 470890 470889 469890 468892 468893 467895
      468898 470896 470895
 0.25 469856 468854 468853 467852 465853 465854 464856 465858
      467860 468858 468857 469856
 0.25 454855 454852 454850 454847 453846 451845 450845 449845
      447846 446848 445851 445853 445855 446857 447858 448858
      450858 451858 452857 453856 454855
 0.25 433771 433768 433766 431764 430764 430766 430769 431771
      431773 432774 433773 433771
 0.25 423796 423794 423792 421789 419789 417789 416790 416791
      415793 415795 415797 415800 416802 417804 419806 420805
      422803 423801 423799 423797 423796
 0.25 427862 426860 426859 424858 424857 422858 423860 424861
      425862 426863 427862
 0.25 411068 410066 409065 407064 405065 404065 403065 402067
      403069 403070 405071 406072 408072 410070 411068
 0.25 258972 258968 257967 254965 250963 246962 241961 237962
      234965 235971 238973 243975 248975 253974 257972 258972
 0.25 247806 248802 244802 241801 237804 236806 235808 234811
      235813 237815 240814 244813 245811 247809 247806
 0.50 493269 495259 494252 493246 490241 483234 479232 475230
      471229 471226 475222 479221 485224 488226 493228 495223
      495218 493210 489207 482204 477204 469207 461208 452211
      443213 433214 426217 423225 420228 419224 419220 417215
      410210 401205 382193 377191 375191 374194 376199 378202
      386210 394217 398220 399226 391226 385226 382227 381231
      388240 395246 400248 405250 426249 432248 434250 441248
      452248 463249 472256 477262 481267 486270 491271 493269
 0.50 471158 472153 471150 469145 465140 460140 454149 449149
      445146 439138 436138 434140 432145 431149 432154 434158
      438163 441166 450171 451175 452177 455174 457165 460163
      469160 471158
 0.50 446106 446104 443101 439100 435100 433096 429094 431099
      430104 425105 422109 419112 412112 409109 405111 402116
      406120 409122 421126 426123 429120 437114 442113 445109
      446106
 0.50 252970 252969 251968 250967 248967 246967 244966 243966
      241966 239967 238967 238969 239971 241971 241972 243972
      244972 246972 248972 250971 252970 252970
 1.00 486251 484246 483242 480237 477235 474235 470236 467238
      466242 469245 474249 477251 482253 485252 486251
 1.00 488216 485209 481208 470213 460214 449215 438218 436219
      435223 439227 445228 449226 455223 460223 469219 474215
      479215 485214 488216
 1.00 447160 448158 448157 446156 446155 445153 443152 442152
      441151 439152 439153 439155 439156 440159 441159 442160
      444160 446161 447160 447160
 1.00 423241 421237 416234 413232 410229 408232 403233 400237
      402242 406244 411246 414245 419245 422243 423241
 1.00 413221 414217 412215 407212 402208 397205 393202 389200
      386199 384203 385205 390210 394213 399216 405216 410220
      411223 413221
 1.50 451220 450219 449218 447217 445218 443220 442222 443223
      444223 445223 446223 448222 449222 450220 451220
 1.50 400213 401211 400210 399208 397207 396206 395205 394204
      392204 390203 389203 390205 390206 392208 392209 393210
      395212 396213 398213 400213 400213 

24HR QP VT 11/12Z
 0.01 512250 513245 512240 510235 509230 506222 506214 505209
      501199 502193 506192 511197 515200 516196 517189 517185
      516182 511171 509167 506162 500156 498150 497145 491140
      489134 489125 488111 486087 487073 486068 486061 484032
      481020 482005 479992 474980 468958 466945 467931 470920
      474912 477904 480892 480879 479868 475840 470816 461797
      453773 451769 450765 451762 456752 456744 453740 451738
      445738 441739 436740 430746 425752 419759 414767 411776
      409783 408789 404798 403808 399820 396832 391842 387849
      383857 378866 373873 363887 358894 353899 342913 334920
      327926 320931 312937 306941 301945 296947 285957 281961
      277964 274966 270969 260969 254968 253972 255976 258977
      262978 266978 277976 286979 295983 303983 336971 343964
      348956 354947 359937 368923 373916 378911 395902 406900
      407905 408912 412925 415937 419947 419958 422979 424985
      426989 430999 438015 442024 444032 447042 447050 445056
      433071 440077 443079 443082 443086 441088 436090 432087
      425081 424075 425067 428058 425049 424046 418045 413040
      407039 404040 399040 397039 391038 388039 381047 376048
      372050 370052 372055 378056 381060 379062 376061 371061
      368062 366064 367070 366077 368083 373093 376096 382097
      386100 387107 381115 375119 373124 373129 379133 384134
      387134 388138 390150 388166 386173 386175 389178 388182
      383182 377180 366177 356176 350182 353222 357230 365236
 0.01 365236 377245 383249 392251 409257 424264 441269 447269
      455271 458270 463271 468273 484279 488280 491280 498279
      503278 507277 507274 507268 508262 511252 512250
 0.01 442200 441195 439190 435187 433186 430188 428189 425193
      424200 426205 429209 432211 436211 439207 440202 442200
 0.01 270798 270789 269785 266783 253781 245782 239785 235788
      232794 230808 229824 230833 231838 233840 239840 244836
      249824 251818 255813 263804 268800 270798
 0.25 495254 497247 497242 495235 495230 496224 497218 498212
      496208 489202 480203 464209 455211 447212 438215 430217
      426218 422221 419220 417216 415205 411202 406201 372182
      367181 363182 359186 361191 366198 372206 378214 380217
      379220 377219 372216 368216 367220 370224 377230 381232
      387234 400244 441254 450253 459252 465252 469253 478256
      488258 493257 495254
 0.25 486167 487161 487156 484148 482140 475139 467139 460139
      447145 442147 436150 435155 437160 442164 445166 448169
      448180 449188 453189 456188 462185 467179 472176 478173
      483171 486167
 0.25 448111 449106 448101 439099 433095 430093 428096 428101
      424102 416102 413101 410099 408098 406100 395109 389113
      384117 384122 387124 397124 405128 408129 411129 417127
      423124 428118 434116 441115 448111
 0.25 454979 454970 452963 449955 448947 446940 447934 443918
      441900 440890 438882 438873 438869 440866 440862 439859
      436852 434847 430841 427839 423841 420844 416849 416859
      415867 416875 417883 418893 422908 427922 428930 429940
      429949 430957 434973 436979 440985 443991 446998 449001
      451000 453995 453984 454979
 0.25 419168 420157 419149 415141 413139 410136 405142 400148
      397154 396163 397169 398173 403178 405180 409180 412179
      414177 418170 419168
 0.25 415073 416067 415062 412059 407056 402057 398059 391062
      387063 384067 381069 379074 381078 384079 388078 390082
      392083 393080 397079 404076 409076 413075 415073
 0.25 396226 396224 395223 393221 392221 392220 390219 388219
      386219 384219 383221 383223 384224 384225 385227 386228
      386229 388229 389229 390229 392228 393228 394227 396226
 0.25 257799 258795 256792 251792 246794 242799 240803 238809
      237815 237820 239822 243821 246817 248812 251808 254803
      257799
 0.50 492219 492214 490208 485205 481206 464211 456214 447215
      440218 432222 430225 433229 436233 438238 440241 445243
      455244 463243 468242 471244 476246 481247 484243 482238
      479234 476232 468230 469225 473222 476220 481219 488222
      492219
 0.50 473163 474161 475159 475156 474155 473153 472153 471152
      469152 467152 465154 465157 466159 468161 469162 469163
      471163 473163 473163
 0.50 417239 417234 415231 413227 414224 415220 413217 411213
      408211 396201 385193 378189 371185 367184 365186 365192
      366195 371200 377205 390213 397217 402223 403226 403230
      401234 401238 404240 407242 411242 415241 417239
 0.50 413118 412114 410110 409108 407106 404107 402108 400110
      398111 397115 399117 401118 404119 408120 410119 413118
 0.50 410070 410068 410067 410066 409064 407063 405063 403064
      403065 402067 403068 405069 406070 408071 410070 410070
 0.50 250800 248800 247800 246801 245803 244803 243805 242807
      242809 243811 244812 245811 246811 247809 247808 248806
      249806 249804 250802 250801 250800
 1.00 454221 455218 454218 452217 451217 450218 449218 447219
      445220 443220 442222 443224 444224 446223 448223 450223
      451222 452222 453221 454221
 1.00 395207 392202 389200 386197 382195 378192 374191 371192
      373196 376200 380203 383206 388208 391209 395207
 1.50 391204 390204 389203 388201 387201 386200 384198 382197
      381196 379196 378196 379198 379199 380200 381202 382202
      383203 385204 387205 389204 390204 391204 

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
833 AM EST THU DEC 08 2016

...VALID 15Z THU DEC 08 2016 - 12Z FRI DEC 09 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...



THE PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE IS LESS
THAN 2 PERCENT.

ORAVEC

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
352 AM EST THU DEC 08 2016

VALID 12Z THU DEC 08 2016 - 12Z SUN DEC 11 2016


DAYS 1-3...


...PACIFIC NORTHWEST AND NORTHERN CALIFORNIA TO THE NORTHERN AND
CENTRAL ROCKIES...

A WIDESPREAD WINTER WEATHER EVENT IS EXPECTED TO IMPACT LOCATIONS
FROM THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA TO THE NORTHERN
AND CENTRAL ROCKIES THU INTO THE WEEKEND. ARCTIC AIR CURRENTLY
ENTRENCHED ACROSS THE WESTERN U.S. WILL BE SLOW TO SCOUR OUT OVER
THE NEXT FEW DAYS...WHILE WARM MOISTURE AIR ADVANCING OUT AHEAD OF
AN APPROACHING PACIFIC SYSTEM WILL OVERRIDE THE TRAPPED COLD AIR
AND PRODUCE WINTRY PRECIPITATION DOWN TO TO NEAR SEA OVER THE
PACIFIC NORTHWEST THURSDAY AND THURSDAY NIGHT. ACCUMULATING SNOW
AND PATCHES OF FREEZING RAIN WILL SPREAD NORTHEASTWARD FROM
NORTHERN CALIFORNIA INTO THE PACIFIC NORTHWEST AND INTERMOUNTAIN
WEST BEFORE SOUTHWESTERLY WINDS DEEPEN DOWN TO THE SURFACE AND
KEEP SNOW CONFINED TO THE HIGHER ELEVATIONS OF THE SIERRA NEVADA
AND CASCADES. PRECIPITATION WILL CONTINUE TO EXPAND
EAST-NORTHEASTWARD FRIDAY IN TO THE WEEKEND... SHIFTING THE FOCUS
FOR WINTER WEATHER INTO THE NORTHERN/CENTRAL ROCKIES.
MEANWHILE...CONTINUED WAVES OF LOW PRESSURE ALOFT ALONG WITH DEEP
WESTERLY (ONSHORE) MOIST FLOW WILL SUPPORT ADDITIONAL PERIODS OF
HEAVY SNOW ALONG THE WASHINGTON AND OREGON CASCADES OVER THE
WEEKEND.


...NORTHERN PLAINS/UPPER MISSISSIPPI VALLEY...

THE INITIAL BATCH OF UPPER LEVEL SHORTWAVE ENERGY RESPONSIBLE FOR
THE WINTER WEATHER LATE THIS WEEK ACROSS THE WESTERN U.S. WILL
MOVE QUICKLY INTO THE THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY OVER THE WEEKEND. THIS SYSTEM WILL BE ACCOMPANIED BY A
RELATIVELY NARROW STRIPE OF DEEP MOISTURE...WHICH WILL IN TURN
GENERATE AN ELONGATED AREA OF LIGHT TO MODERATE SNOW FROM THE
DAKOTAS EAST-SOUTHEAST THROUGH THE UPPER MIDWEST. THE HEAVIEST
SNOW...I.E. PROBABILITIES OF 40-60 PERCENT OF AT LEAST 4
INCHES...IS ANTICIPATED ALONG A NARROW AXIS CORRESPONDING TO THE
STRONGEST DEEP-LAYER FRONTOGENESIS...WHICH AT THIS POINT REMAINS
TOUGH TO PINPOINT (LOW FORECAST CONFIDENCE) GIVEN THE CONTINUED
LATITUDINAL SPREAD AMONG THE 00Z GUIDANCE WITH RESPECT TO THE
WHERE THE MORE FAVORABLE UPPER JET FORCING WILL SET UP ALONG WITH
TIMING/AMPLITUDE DIFFERENCES WITH THE SHORTWAVE AND EVENTUAL
(ALBEIT WEAK) SURFACE REFLECTION. THE LATEST WPC ENSEMBLE BLEND
FOR DAY 3 (12Z SAT-12Z SUN) ESSENTIALLY SPLITS THE DIFFERENCE
BETWEEN THE GFS AND ECMWF...AS THE 00Z ECMWF FINALLY DEPICTS A
SHORTWAVE MOVING INTO THE CENTRAL U.S. (TRENDING TOWARD THE GFS IN
THAT RESPECT)...THOUGH THE ECMWF REMAINS ONE OF THE MORE LIGHTER
RUNS (AMONG BOTH OPERATIONAL AND ENSEMBLE GUIDANCE) WITH RESPECT
TO THE QPF. A PSEUDO-BLEND OF THE GFS-ECMWF-UKMET WAS
UTILIZED...WHICH WAS CLOSE TO THE GFS AS THE WETTER UKMET TENDED
TO OFFSET THE DRIER ECMWF. PLEASE REFER TO WPC'S MODEL DIAGNOSTIC
DISCUSSION (PMDHMD) FOR MORE DETAILS ON MODEL SPREAD.


...GREAT LAKES...

SNOW SHOWERS ARE EXPECTED DOWNWIND OF THE GREAT LAKES OVER THE
NEXT COUPLE OF DAYS AS WINDS INCREASE AND TEMPERATURES DECREASE
WITH AN UPPER TROUGH PROGRESSING FROM THE NORTH CENTRAL TO
NORTHEASTERN U.S..  THE HIGHEST SNOWFALL TOTALS SHOULD BE OVER THE
FAVORED NNW SNOWBELTS IN WESTERN-CENTRAL UPPER MI AND NORTHWEST
LOWER MI...AS WELL AS THE WESTERLY FLOW SNOWBELTS DOWNWIND OF
LAKES ERIE AND ONTARIO.  ACTIVITY SHOULD DECREASE A BIT ON
SATURDAY WHILE THE UPPER TROUGH MOVES OFF THE ATLANTIC COAST AND A
SHORTWAVE RIDGE BRIEFLY BUILDS IN ALOFT.    

HURLEY

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 AM EST THU DEC 08 2016

VALID 12Z SUN DEC 11 2016 - 12Z THU DEC 15 2016

...ARCTIC AIR TO SURGE INTO THE LOWER 48 NEXT WEEK...


...PATTERN OVERVIEW...

A MIDDLE/UPPER-TROPOSPHERIC CLOSED LOW REMAINS FORECAST TO DROP
SOUTHWARD FROM NUNAVUT THIS WEEKEND AND THEN TURN EASTWARD THROUGH
SOUTHERN CANADA DURING THE MIDDLE OF THE NEXT WEEK.
UNDERNEATH...UNCERTAIN NORTHERN PACIFIC SHORTWAVE ENERGIES
PROGRESS FROM THE NWRN US/CA THROUGH THE INTERMOUNTAIN W/ROCKIES
SUN INTO MON IN GENERAL LOWER 48 ZONAL FLOW LEADING TO SOME
CENTRAL US AMPLIFICATION AHEAD OF THE NRN STREAM CANADIAN UPPER
LOW. A BROAD CYCLONIC CIRCULATION WITH UNCERTAIN NRN STREAM
INFLUENCE ALOFT SHOULD THEN ENCOMPASS THE EASTERN HALF OF THE
LOWER 48 INTO NEXT WED/THU AS ADDITIONAL PACIFIC IMPULSES WORK
BACK TO THE WRN STATES.

...GUIDANCE PREFERENCES...

GUIDANCE QUESTIONS ARISE WITH HOW PACIFIC SHORTWAVES ZIP THROUGH
THE FLOW ACROSS THE CONUS NEXT SUN-MON AHEAD OF THE INTENSE COLD
SURGE FROM THE NORTH. BIGGER QUESTIONS INTO MIDWEEK CONCERN THE
EXTENT OF NRN STREAM HEIGHT FALLS WORKING INTO THE NWRN US ALONG
WITH POTENTIALLY MORE ERNEST NRN AND SRN STREAM TROUGH HEIGHT
FALLS/PHASING DOWNSTREAM OVER THE E-CENTRAL US. GUIDANCE HAS NOT
BEEN VERY CONSISTENT WITH EMBEDDED IMPULSE TIMING/SFC DEFINITION
OUT FROM SHORT RANGE TIME SCALES INTO EARLY NEXT WEEK LENDING A
COMPOSITE SOLUTION. HOWEVER...CAN THE ARCTIC SURGE SPIN UP
DEEPENING LOW PRESSURE ALONG THIS LEADING FRONT TO SLOW ITS
PROGRESSION EASTWARD NEXT TUE/WED AS CHAMPIONED BY RECENT GFS
RUNS? WPC PROGS DO NOT EMPHASIZE THIS HEAVIER RAIN AND NORTHWARD
WINTER WEATHER THREAT AT THIS POINT...BUT IT REMAINS POSSIBLE
CONSIDERING NRN STREAM AMPLITUDE EXTENDING THROUGH ALASKA.


...WEATHER HIGHLIGHTS/THREATS...

PERSISTENT WEST TO EAST MID-LEVEL FLOW WILL KEEP THE WESTERN
REGION ACTIVE, ESPECIALLY OVER NORTHERN CALIFORNIA NORTHWARD ALONG
THE COASTAL RANGE AND CASCADES. ADDITIONAL UPLIFT VIA THE ARCTIC
BOUNDARY MOVING OUT OF MONTANA WILL PROVIDE ANOTHER MECHANISM FOR
SNOWFALL OVER THE BITTERROOTS AND SAWTOOTH RANGE AND BROAD
VICINITY. GENERALLY ABOVE AVERAGE TEMPERATURES WILL CONTINUE FOR
THE SOUTHWESTERN FIFTH OF THE CONUS (CA/NV/UT/AZ AND WESTERN
CO/NM).

WITH THE FORECAST ARCTIC SURGE COMING OUT OF SOUTHWEST CANADA INTO
THE N-CENTRAL US...AN IMPRESSIVE AREA OF WELL BELOW AVERAGE
TEMPERATURES WILL RUSH SOUTHWARD AND EASTWARD FROM THE NORTHERN
HIGH PLAINS THROUGH THE MIDWEST AND EVENTUALLY TO THE EAST COAST
BY WED/THU NEXT WEEK. TEMPERATURES MAY BE 20-30 DEGREES BELOW
AVERAGE AND MAY FLIRT WITH SOME RECORDS (PERHAPS RECORD LOW
MAXIMA) THOUGH THE LONGER PERIOD STATIONS GENERALLY HAVE SOME VERY
COLD RECORDS BY NOW (MID-DECEMBER).

NW FLOW AND COLD AIR OVER THE GREAT LAKES SHOULD SUPPORT A
MULTI-DAY LAKE EFFECT EVENT FROM MICHIGAN EASTWARD THROUGH NE
OHIO/NW PA INTO WESTERN/CENTRAL NY INCLUDING THE TUG HILL PLATEAU.
TRACK OF THE EXITING SFC LOW AND INCOMING SFC HIGH WILL DETERMINE
WHO SEES THE MOST SNOW...BUT SETUP LOOKS GOOD PROVIDED ENOUGH
MOISTURE CAN BE WRUNG OUT IN THE OVERALL DRY/COLD AIRMASS. GLOBAL
MODELS/ENSEMBLES GENERALLY HAVE A GREEN LIGHT FOR AT LEAST
LIGHT-MODERATE SNOW NEXT TUE-THU (AND PERHAPS BEYOND).


SCHICHTEL