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Area Forecast Discussion
Issued by NWS Boston, MA
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FXUS61 KBOX 010421
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1121 PM EST Tue Jan 31 2017

.SYNOPSIS...
Low pressure will bring a widespread accumulating snowfall to the
region this evening into early Wednesday. The remainder of the
week will trend colder with blustery conditions at times. Another
shot of snow is possible sometime late Sunday into Monday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...

1050 PM Update...

First batch of steady light snow has been shifting slowly NE off
the Mass coast over the last couple of hours. However, still
noting light snow being reported at most stations across the
region at 03Z, though cloud bases and visibilities have improved.
This lull should last through around 1 AM.

The next short wave will work eastward through the overnight out
of the eastern Great Lakes as seen on latest water vapor satellite
imagery. Organized area of snow associated with this wave will
steadily shift out of central NY into central and N Mass, mainly
near and N of the Mass Pike. May see pockets of briefly moderate
snow as this next area moves through. Could see another inch or
so with this system.

Have kept previous forecast of 2-4" snow total by the time this
event winds down. Expect back edge of the snow to push NE around
of after 3 AM.

Kept the winter weather advisory intact due to continued slippery
roadways especially on secondary roads.

Remainder of forecast looks good. Noting temps remaining steady or
slowly rising through the night. Readings in the mid 30s on the
outer Cape and the islands, with a report of light rain at KCQX at
04Z.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Tomorrow...

Surface low will move northward tomorrow pushing any remaining snow
showers with it. Zonal flow will dominate across the region with mid-
level dry air aloft. Appears that there is some low level moisture,
combined with steep lapse rates may result in some snow showers
across the western half of the region. But the potential for
accumulating snowfall with these showers appears low at this time.
Aside from a passing snow shower, anticipate a mainly dry day as
temperatures will rebound in the upper 30s to low 40s.

Biggest issue tomorrow will be the gusty winds. 925 mb jet increases
to 30 kts. This mixing down could result in some gusts between 20-30
mph.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Highlights...

* Trending colder and blustery at times Thursday into Saturday
* Chance of snow sometime Sun-Mon, but confidence in the details
  remains low

Overview...

As noted by previous forecaster, mid level pattern through the
extended still has an anomalous ridge over Alaska, with a polar
vortex over Hudson Bay slowly drifting east across Canada. The
resulting broad longwave trough will change its angle of approach to
southern New England at times. The exact angle of this steering flow
will have a significant effect on precipitation type, or if we see
storms at all.

Most of this period looks dry. A couple of storms may impact our
region, one on Sunday, and one toward the middle of next week.
ensemble spreads are large with both of these storms, so very little
confidence in the details.

Wednesday night through Saturday...

Our region should remain beneath the mid level trough, with limited
moisture. Depending upon the wind direction, there could be enough
Great Lakes moisture to result in some flurries/light snow showers.
Otherwise, just expecting scattered clouds at times, more likely
toward the Berkshires. Temperatures become closer to normals, or
perhaps slightly below.

Sunday into Monday...

Lots of spread in the ensemble members, and differences persist in
the deterministic solutions, too. General theme is for a low
pressure to pass south of our region. Will likely need to wait a
couple more days for the energy that will become this low pressure
to become better sampled over western North America, before we get
more clarity on the details. Ensemble probabilities still indicate a
low risk for significant precipitation. Will just need to watch this
closely later this week.

Tuesday...

Unlike the potential Sunday storm, this storm appears to be passing
by to our north. So, not looking like a snow storm at this time.
Same uncertainty limitations discussed above apply here, too.

&&

.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Overnight...Moderate confidence, mainly due to timing issues.
Mainly MVFR-IFR CIGS across most of the region with a variety of
VSBYS, ranging from VFR along the S coast to MVFR-IFR across N
central and E Mass from KOWD northward. Conditions will lower
again across central and N Mass as another area of -SN moves
across from 05Z-09Z. Low chance for LIFR conditions at times with
this precip. Conditions should slowly improve to VFR from south
to north between 09Z-12Z.

Wednesday...Moderate confidence.
Leftover -SN and MVFR CIGS through late morning across N central
and NE Mass. Otherwise mainly VFR, except MVFR conditions may
linger across the E slopes of the Berkshires through the day in
scattered snow showers. W winds gusting up to 30 kt along S coast,
Cape Cod and the islands.

KBOS TAF...Moderate confidence. MVFR/IFR with -SN this evening.
Could see LIFR during the overnight hours. Conditions should
improve by Wednesday morning.

KBDL TAF...Moderate confidence. IFR and occasionally LIFR in
heavy snow bands will continue over the next few hours. Conditions
will improve closer to 3-6z.

Outlook /Wednesday Night through Sunday/...Moderate confidence.

Mostly VFR cigs with areas of MVFR at times, especially across the
higher terrain of central and western MA. Gusty NW winds to 25 kt
at times, mainly from mid morning into late afternoon, each day.

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Overnight...High confidence. Low pressure moves out of Mass Bay to
the western Gulf of Maine. Expect E-SE winds to shift to W and
increase on the southern waters, with light E-NE winds over the
eastern waters to shift to W after 08Z-09Z. Snow will continue
over the waters tonight. Closer to daybreak, west winds will
begin to increase as stronger low level winds move across the
waters.

Wednesday...Moderate to high confidence. Westerly winds will
continue through the day as stronger low level winds continue to
increase Wednesday morning. Have issued a gale warning across the
southern waters where gusts between 35-40 kts are possible per
BUFKIT soundings. SCA will continue elsewhere.

Outlook /Wednesday Night through Sunday/...Moderate confidence.

W/NW flow through the period with gusts to 20-30 kt at times.
Anticipating a long period of small craft advisories due to winds
and/or seas, especially across the outermost coastal waters.
Strongest gusts expected Saturday, with a low risk for gales. Winds
expected to turn more SW Sunday.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory until 4 AM EST Wednesday for
     CTZ002>004.
MA...Winter Weather Advisory until 4 AM EST Wednesday for
     MAZ002>022-026.
RI...Winter Weather Advisory until 4 AM EST Wednesday for
     RIZ001>007.
MARINE...Gale Warning from 10 AM to 3 PM EST Wednesday for ANZ232>234.
     Small Craft Advisory from 1 PM to 7 PM EST Wednesday for
     ANZ230.
     Small Craft Advisory from 7 AM to 7 PM EST Wednesday for
     ANZ231-250-251.
     Small Craft Advisory from 5 AM to 7 PM EST Wednesday for
     ANZ236.
     Gale Warning from 5 AM to 3 PM EST Wednesday for ANZ235-237-
     256.
     Gale Warning from 5 AM to 7 PM EST Wednesday for ANZ254-255.

&&

$$
SYNOPSIS...Belk/Dunten/EVT
NEAR TERM...Belk/EVT
SHORT TERM...Dunten
LONG TERM...Belk
AVIATION...Belk/Dunten/EVT
MARINE...Belk/Dunten/EVT
National Weather Service Regional Headquarters
