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Area forecast discussion 
National Weather Service Taunton Massachusetts
547 am EST Sat Jan 31 2015

Synopsis...
blustery and very cold conditions continue through the weekend. A
major winter storm will affect the region Sunday night into
Monday evening with potentially heavy snow accumulation and gusty
winds. A frigid airmass will follow Monday night with dangerously
cold wind chills. Moderating temperatures Wednesday then very cold
conditions will return toward the end of the week. A coastal storm
will pass well south of New England late in the week but will
have to be monitored.

&&

Near term /through tonight/...
middle level low closing off near Cape Cod with bands of light
snow rotating back across east Massachusetts. Higher reflectivities are
developing on radar across east coastal Massachusetts and the adjacent waters
indicating steadier snow. Model guidance suggest some quantitative precipitation forecast
enhancement over the Outer Cape through the morning within the
developing comma head. Main focus for minor accumulate through middle
morning will be across Cape Ann and the Outer Cape where 1-2
inches is possible. Low probability for isolated 3 inch amounts Outer Cape.
Elsewhere across east Massachusetts...mainly a coating to one half inch.

Areas of light snow will linger across east Massachusetts into the
morning...exiting the Outer Cape by midday. Clearing skies
develop across east new eng later this morning into the
afternoon...with full sunshine across the west.

Strong northwest winds will continue today. Gusts 35-45 miles per hour expected with
a few gusts near 50 miles per hour near the coast.

Bitter cold wind chills down to -10 to -20 this morning across
central and west new eng and -5 to -10 in the coastal plain.
Afternoon high temperatures only in the teens most locations but with the
strong winds...wind chills will only recover to -5 to +5.

&&

Short term /Sunday/...
tonight...

Weak surface ridge moves into the region ahead of Arctic front
dropping into north new eng. This will result in gradual diminishing
winds tonight...but remaining rather gusty over the cape/islands
through the night. Min temperatures will drop into the single numbers
with teens along the immediate coast and cape/islands.

Sunday...

Arctic front will push S into southern New England reaching the S coast by evening.
Sunshine will give way to increasing clouds in the afternoon as
overrunning middle/high clouds move into the region...along with
development of some lower clouds as low level moisture increases.
But remaining dry through the day. High temperatures mostly in the
middle/upper 20s but dropping back into the teens toward evening
across north zones as Arctic air begins to drain south.

&&

Long term /Sunday night through Friday/...

Highlights...

* low pressure passes S of New England Sun night and Monday...cold air in
place signals plowable snowfall for the region
* Winter Storm Watch extended to cover entire region
* as low exits Monday night...more Arctic air and strong winds move
in...wind chill headlines likely
* record lows possible Tuesday morning with high pressure
* another low possible Wednesday or Thursday...low confidence continues

Overview...

Models and ensembles continue to signal progressive pattern but
general long wave troughing across the eastern U.S. Through most of
the long term period. Several 500 mb short waves in northern stream flow
during this timeframe. Very cold air will remain across the region
through Tuesday...then temperatures will rise closer to seasonal normals
around middle week. Another Arctic front and possible low pressure may
bring another round of wintry precipitation around Wednesday or Thursday.

Details...

Sunday night through Monday night...
vigorous 500 mb short wave and associated surface low pressure move out
of the Ohio Valley to the middle Atlantic coast by 12z Monday. By then...
though...excellent overrunning in place with deep moisture feed
working into the region. With cold air already in place...and high
pressure moving in tandem across southern Canada... will not be
displaced. Expect light snow to spread across the region Sunday
night.

As the low moves off the middle Atlantic coast...will see strong
intensification of the system as it moves along 40n latitude
before turning NE near the 40n/70w benchmark Monday evening.
Excellent dendritic growth with Arctic airmass...so expect periods
of moderate to heavy snowfall especially Monday morning through
midday as the low passes to the S. Looks like the heaviest
snowfall will occur S of the Mass Pike...but the entire region
will see a good amount of snowfall. Only question at this point
will be whether a piece of somewhat milder air aloft will work
into the Outer Cape and islands which could cause a brief mix with
sleet or even rain Monday morning or midday. Once the low
passes...though...will change quickly back to snow there during
the afternoon.

With the snow arriving Sunday night...can expect at least light
snow accumulations by the time of the start of the Monday morning
commute. Expect a rough commute if anyone even ventures out of
doors Monday morning. Visibilities will also be reduced as well.

With all models in very good agreement...and quantitative precipitation forecast totals on order
of 0.6 to 1.1 inches from north-S across the region and cold airmass
in place...will see snow to liquid ratios around 13:1 or so pretty
much everywhere except around 10:1 on the Outer Cape and the
islands. With this in mind...have updated the Winter Storm Watch
to include the entire region...adding northern Massachusetts and
the islands to the watch.

The low will intensify rapidly as it exits late Monday and Monday night.
Increasing pressure gradient will cause north-northwest winds to increase...with
gusts up to 30-40 miles per hour or higher especially along the East Coast.

As for coastal flooding...it appears that the stronger north-NE winds
will occur around the time of low tide Monday afternoon. Could see
up to one or two feet...but because the surge is not coinciding
with high tide...we do not expect issues at this time. Will
continue to monitor this aspect closely though.

Temperatures Monday night will plummet as another shot of Arctic
air works in. Expect overnight lows to come close to record lows
during the pre-dawn hours of Tuesday morning. Mainly locations will
likely see readings below zero...except along the immediate S
coast...Cape Cod and the islands. Please see the climate section
below for the records.

Tuesday...
high pressure ridge builds across. Will see blustery conditions early
Tuesday...but cold air remains in place. Expect highs only in the
teens...ranging to around 20 along the immediate S coast.

Wednesday-Thursday...
the high pushes offshore on Wednesday...with a return flow of milder
air. Temperatures Wednesday into Thursday may actually rebound close to seasonal
normals with light SW winds.

Big question at this point will be the approach of a cold front
out of central Canada along with the development of low pressure. Not
a lot of confidence at this point due to wide model variance. For
now...have mentioned chance of precipitation...mainly light snow...as
cold front passes around Wednesday night or early Thursday.

Friday...
another high looks to build east with more cold air...but timing is
uncertain.

&&

Aviation /12z Saturday through Wednesday/...
forecaster confidence levels...

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

Short term.../through Sunday/...high confidence.

Through today...N-S band of -sn with MVFR conditions will be
confined to east Massachusetts shifting to just Cape Cod after 12z before ending
by midday over the Outer Cape. Otherwise...VFR with clearing skies
in eastern new eng. Northwest gusts to 30-40 knots.

Tonight...VFR with gradual diminishing wind.

Sunday...mainly VFR...but low probability for areas of MVFR ceilings
developing in the afternoon.

Kbos taf...high confidence. MVFR visibilities due to light snow and
blowing snow early this morning. Improving conditions after 12z.

Kbdl taf...high confidence.

Outlook /Sunday night through Wednesday/...

Sunday night into Monday night...moderate confidence.

VFR to start...then quickly deteriorating conditions to IFR-
vlifr with snow moving in from W-E. Periods of heavy snow possible
Monday morning into midday. Blustery NE winds with gusts up to
around 30 knots starting Monday afternoon then veer to northwest but remain
gusty Monday night. Conditions improve from west-east Monday night...but lower
ceilings/visibilities may linger along East Coast through most of the night

Tuesday...moderate confidence. Mainly VFR. Northwest wind gusting to 25-30
knots early then should diminish.

Wednesday...moderate confidence. VFR through midday. May see MVFR
conditions move into north Massachusetts during the afternoon in snow showers.

&&

Marine...
forecaster confidence levels...

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

Short term /through Saturday night/...high confidence.

Today...gale center lifts into the Maritimes with northwest gales
continuing over the waters. Gusts to 40-45 knots likely with
moderate freezing spray likely. Snow showers reduce visibility over
eastern Massachusetts waters in the morning.

Tonight...gale center pulls farther away with winds diminishing
below gale 00-06z...but gusts 25-30 knots will continue overnight.
Moderate freezing spray likely continuing...especially east Massachusetts
coastal waters.

Sunday...winds and seas gradually diminish through the day. Sub
Small Craft Advisory conditions develop over the S coastal waters during the
morning...but Small Craft Advisory conditions will continue across the outer
eastern waters. Light freezing spray will persist.

Outlook /Sunday night through Wednesday/...

Sunday night...moderate confidence.
Winds back from northwest to north during the night...gusts increasing to
around 20 knots on the southern outer waters. Visibilities lower in
developing light snow from W-E.

Monday and Monday night...moderate confidence.
Expect increasing east-NE winds...gusting up to 35-40 knots late Monday
and Monday night. Seas building as high as 14-17 feet on the eastern
waters as low pressure intensifies as it passes S of the southern
waters. Winds shift to northwest but remain gusty Monday night. Reduced
visibilities in snow...falling heavily at times.

Tuesday...moderate confidence.
Northwest winds continue to gust close to gale force through the morning
then will diminish but remain at small craft criteria. Seas remain
high...up to 8-10 feet but will slowly subside. Winds may diminish
below small craft Tuesday night...but seas may linger around 5 feet.

Wednesday....moderate confidence.
Winds back to SW and increase...may see gusts up to 25-30 knots.
Seas also remain around 5 feet...mainly over the outer waters.

&&

Climate...
with extremely cold air moving in behind the departing low Monday
night...temperatures may fall back close to or surpassing record
levels early Tuesday morning. And that is not taking into account
the strong winds.

Here are the record lows for Tuesday 2/3...

Boston -5 set in 1881
Providence -6 set in 1961
Worcester -7 set in 1931, 1955 and 1971
Windsor Locks -3 set in 1955
Blue Hill observation -7 set in 1955

&&

Box watches/warnings/advisories...
CT...Winter Storm Watch from Sunday evening through late Monday
night for ctz002>004.
Wind Chill Advisory until 9 am EST this morning for ctz002-003.
Massachusetts...Wind Advisory until 9 PM EST this evening for maz022>024.
Winter Storm Watch from Sunday evening through late Monday
night for maz002>024-026.
Wind Advisory until 6 PM EST this evening for maz007-015-016-
019>021.
Wind Chill Advisory until 9 am EST this morning for maz003-004-
010-011.
Wind Chill Advisory until 11 am EST this morning for maz002-
008-009.
Rhode Island...Wind Advisory until 9 PM EST this evening for riz008.
Winter Storm Watch from Sunday evening through late Monday
night for riz001>008.
Wind Advisory until 6 PM EST this evening for riz005>007.
Marine...freezing spray advisory until 6 am EST Sunday for anz231-232-
250-251.
Gale Warning until 1 am EST Sunday for anz231-232-250-251-
254>256.
Freezing spray advisory until 6 PM EST this evening for
anz233>235-237.
Gale Warning until 10 PM EST this evening for anz233>235-237.
Gale Warning until 9 PM EST this evening for anz230.
Gale Warning until 6 PM EST this evening for anz236.

&&

$$
Synopsis...kjc
near term...kjc
short term...kjc
long term...evt
aviation...kjc/evt
marine...kjc/evt
climate...evt

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