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Area forecast discussion 
National Weather Service Taunton Massachusetts
700 am EST Sat Feb 13 2016

Synopsis...
an Arctic front will deliver dangerously cold wind chills of 20 to
35 below zero later today into Sunday morning. A period of
accumulating snow and ice is then likely for much of region
especially away from the coast Monday afternoon and evening. A
powerful storm system will likely track west of New England
Tuesday/Tuesday night bringing heavy rain...strong winds and warm
temperatures to the region. A trend toward drier and colder
weather follows next Wednesday and Thursday.

&&

Near term /until 6 PM this evening/...
*** Arctic cold front will bring strong wind gusts and a rapid fall
in temperatures this afternoon/early evening ***

7 am update...
Arctic front already moving across the region and approaching the
S coast this morning. A few isentropic enhancement shsn have
developed and are quickly making their exit. Just a very brief and
light snowfall expected...mainly a T of snow any given location.
Otherwise...forecast still on track so made no other adjustments
than to drop the Winter Weather Advisory for ack...as sig snowfalls are
now down there.

Previous discussion...

Distant ocean storm will continue to move further way from the
region early this morning. This will allow the steady snow to come
to an end across the cape/islands between 10 and 12z. Will allow
Winter Weather Advisory to expire at 7 am for Nantucket.

Otherwise...the main story will be the Arctic cold front that will
sweep across the region this morning. Not much low level moisture
available...so other than a brief passing flurry/snow shower it will
come through dry. However...a brutal surge of Arctic air
accompanied by strong wind gusts will result in a rapid fall in
temperatures through the afternoon. 850 temperatures crash to between -26
to -30c by 00z...which is very rare for southern New England
standards. Morning high temperatures mainly in the teens to lower 20s will
plummet through the afternoon/early evening. By early
evening...temperatures will already be below zero across the
interior and single digits along the coastal plain.

Wind gusts will likely over achieve today based on strong pressure
rises behind the front and excellent mixing with such cold air
moving in aloft. Expect northwest wind gusts of 35 to 45 miles per hour with a
few gusts to 50 miles per hour that will develop this afternoon. Wind
advisories were not issued since the strong wind gusts are covered
by the wind chill headlines. By early evening...wind chills will
already have fallen to between 10 and 25 below zero!

&&

Short term /6 PM this evening through 6 PM Sunday/...
*** dangerously cold wind chills of 20 to 35 below zero tonight
into Sunday morning ***

*** coldest low temperatures since January 2004 appear likely in
Boston and Worcester by early Sunday morning ***

Tonight...

Brutal surge of Arctic air will continue to work into the region
tonight. 850 temperatures are expected to be around -30c by 6z
which is extremely rare for this part of the country.
Northwest wind gusts of 35 to 45 miles per hour with a few gusts near 50 miles per hour
will continue tonight. Strongest of those winds will occur during
the first part of the night. The result of the strong winds and
extreme cold will result in wind chill values dropping to between 20
and 35 below zero tonight into Sunday morning.

850 temperatures near -30c will support low temperatures below zero
for all locations except portions of the Outer-Cape cod and
Nantucket. Much of the interior should see low temperatures between 10 and
15 below zero. It is appearing more likely that both Boston and
Worcester will record their lowest temperature in more than a
decade. We are going with a low of 6 below zero in Boston and 12
below in Worcester...both of which would be the coldest since
January of 2004!

Will discuss the concern for another round of accumulating snow
for the Outer-Cape tonight/Sunday morning in our mesoscale section.

Mesoscale setup for the Outer-Cape tonight/Sunday morning...

A rather interesting setup tonight into Sunday morning for the Outer-
Cape. A middle level trough and Arctic shortwave slide south
in southern New England. This will allow for deepening low
level moisture across eastern New England. At the same
time...very extreme instability will develop over the ocean. Delta T
values from the ocean to the top of the mixed layer are near 35c
resulting in ocean induced convective available potential energy near 1500 j/kg. The big limiting
factor will be the wind direction of 300 to 310 degrees...which
normally is too short a fetch for ocean effect. However...this is a
rare case and we should be able to compensate for it with the extreme
instability. In addition...seeder feeder processes with deepening middle
level moisture and synoptic forcing from middle level shortwave. Will
go for 1 to 3 inches of snow tonight into Sunday morning for the
Outer-Cape with a low risk for 4 inches. We will re-issue the
Special Weather Statement to wrap up the early morning snow across
Cape Cod and highlight concerns for tonight/Sunday morning.

There also is low risk for even a few snow showers/flurries
across eastern Massachusetts with middle level shortwave. Some minor accums can
not be ruled out across Cape Ann/upper cape and Nantucket...but main
focus will be across the Outer-Cape.

Sunday...

Dangerously cold wind chills of 20 to 35 below zero will be the main
story through middle morning on Sunday. While it will remain breezy
later Sunday morning and into the afternoon...winds will diminish
some allowing wind chills to improve. Nonetheless...they will
remain below zero all day. High temperatures on Sunday will only
recover into the single digits and lower teens despite plenty of
sunshine. Ocean effect snow showers Sunday morning across the Outer-
Cape will diminish to flurries Sunday afternoon...but clouds may
persist.

&&

Long term /Sunday night through Friday/...
*** dangerously cold wind chills Sunday morning ***

Highlights...

* some accumulating snow and ice likely Monday afternoon/evening
* temperatures in the 50s Tuesday-Tuesday night west/heavy rain and strong winds

Overview and model preferences...

A changeable pattern through the week is expected as the initial
Arctic outbreak from the weekend dissipates and gives way to the
southern stream briefly. However...this is not long lived as a
persistent vortex near baffin island will lead to another
/although not nearly as robust/ Arctic influence as strong riding
amplifies over the western half of the Continental U.S.. this ridging will keep
the Arctic influence short lived as it once again allows for southern
stream dominance by the end of the week. So...in other words...a
bit of a roller coaster with temperatures during the week.

There is reasonable agreement between operational models through
the period...such that a blend of these sources should suffice as
baseline for most of the period. However...will continue with an
ensemble blend for the low pressure passage late Monday into Tuesday...this
is due to its more persistent suggestion of a westerly track when
compared with particularly the GFS operational solution.

Details...

Sun night into Monday...
good setup for radiational cooling Sun night...so thankfully not
as much wind to yield the bitter wind chills of Sat night.
However...with a snowpack and cold h92 temperatures...inversions will
still allow several locations across the interior to drop below
0f... with only single digits near the coast Monday morning. The cold
start...and cresting high pressure will mean temperatures are not going to
rebound as well as they could given the h92 temperatures approach -8c by
afternoon. Increasing clouds Monday with highs in the 20s and low
30s.

Monday evening into Tuesday night...
southern stream low pressure is currently prognosticated to pass west of New England
during the day on Tuesday. Given this has southern stream influence and
Gulf of Mexico moisture...precipitation production will be relatively
efficient with precipitable waters 2 Standard deviations above normal and a 40-50 knots
low level jet. The initial isentropic lift is likely to be snow thanks to a
leftover dome of cold air in advance of the warm advection. Quantitative precipitation forecast
prior to the changeover supports anywhere from 1-4 in of
snowfall..but as mentioned be the previous forecaster...this is
only an initial look until track/thermal profiles are better
resolved. The snowfall could actually increase the risk for some
freezing rain/ice development initially as the changeover to rain occurs
and surface temperatures remain near freezing. However...expect all rain by
about sunrise on Tuesday due to influence of the low level jet. Periods of heavy
rain possible at times Tuesday...with final liquid totals of an inch
or more possible. Moderating temperatures suggest lows near normal but
highs above normal and in the 40s to even near 50 by Tuesday
afternoon.

Wednesday and Wednesday night...
Arctic shortwave will rotate through the much suppressed longwave
trough associated with baffin low cutoff. At this point...it/S
likely this will pass with little fanfare except maybe a few -shsn
thanks to cold advective driven instability. Will need to watch
some offshore wave development...but this appears to be too
progressive for a normal hit...hence the lower end probability of precipitation. Highs in
the 30s and 40s due to the late passage Wednesday evening...overnight
lows in the teens and 20s.

Thursday and Friday...
high pressure associated with cold airmass expected Thursday. 850 mb temperatures
only drop to around -18c as compared to the -30c expected this
weekend. But this is still enough to keep highs Thursday in the 20s and
low 30s and overnight mins in the low teens with a few single
digits. Some warming expected Friday as the high shifts east and allows
modest return flow. Expect highs back in the 30s to around 40 but
mainly dry weather to prevail.

Next weekend...
although there is some uncertainty following the ridging...W-E
traversing wave will approach and currently looks to be yet
another inside runner based on the sharpening trough. Still lot/S
of time here...but conditions look to be more active following the
late week high pressure.

&&

Aviation /11z 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/...

Today...high confidence.
Mainly VFR now...although very brief MVFR possible in a spot -shsn
this morning. Increasing risk for MVFR ceilings later in the day
across the outer arm of Cape Cod and ack. Otherwise...winds
increase through the day...reaching 15-25 knots this afternoon then
25-35 knots by this evening.

Tonight...high confidence. Northwest wind gusts of 30 to 40
knots...strongest of which will occur during the first part of the
night. Mainly VFR except cape/Nantucket where MVFR conditions are
expected in ocean effect clouds/scattered snow showers. Bulk of the
scattered snow showers will be found across the Outer-Cape. Low risk
that a period of MVFR ceilings work into eastern Massachusetts for a time late
tonight.

Sunday...high confidence. Mainly VFR with northwest wind gusts of
20 to 25 knots. The exception will be portions of cape/Nantucket
where MVFR ceilings may persist into the afternoon. Ocean effect snow
showers mainly across Outer-Cape should wind down Sunday afternoon.

Kbos terminal...moderate to high confidence in taf.

Kbdl terminal...moderate to high confidence in taf.

Outlook /Sunday night through Wednesday/...

Sun night into Monday...high confidence.
High pressure yields a period of mainly VFR conditions.

Monday evening into Tuesday night...moderate confidence.
Mix of IFR/MVFR...first as snowfall overspreads the region Monday
night...changing to a mix of rain and possible brief period of
freezing rain. All rain expected on Tuesday. Winds will be shifting
but gusts to 20-30 knots possible mainly during the day Tuesday. Low level wind shear
possible Tuesday as well.

Wednesday...moderate confidence.
Mainly VFR...but brief rain showers/shsn possible.

&&

Marine...
forecaster confidence levels...

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

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

*** Gale force wind gusts and heavy freezing spray expected this
afternoon into Sunday morning ***

Today through Sunday...high confidence. Main story is the
incredibly strong Arctic cold front that will cross the region this
morning. 850 temperatures dropping to between -25 and -30c over the
relatively mild ocean will result in northwest gale force wind gusts
this afternoon into Sunday morning. Extremely cold air/strong winds
will result in areas of heavy freezing spray and Arctic sea smoke.
Gale/freezing spray headlines are in effect into Sunday morning.
Finally...ocean effect snow showers will result in poor visibility
at times.

Outlook /Sunday night through Wednesday/...

Sun night into Monday...high confidence.
Winds and seas will dissipate as high pressure moves over the region.
A period of mainly quiet boating weather is expected after the
winds subside and freezing spray subsides.

Tuesday night into Wednesday...moderate confidence.
A period of at least Small Craft Advisory conditions are expected
as low pressure moves inland. Gusts could reach gale force during the
day on Tuesday...but strong small crafts are expected at least. Waves
reach 8-10ft but then dissipate.

&&

Climate...
bitterly cold temperatures are expected this weekend. Record cold
high and low temperatures may be tied or broken. Here are the
current records for the weekend.

Record cold highs for Feb 13th - 14th...

Boston.......15/1979 - 14/1916
Hartford.....11/1979 - 11/1979
Providence...10/1979 - 10/1979
Worcester.... 8/1899 - 7/1979
Blue Hill.... 9/1899 - 10/1979

Record cold lows for Feb 13th - 14th - 15th...

Boston...... -3/1967 - -3/1934 - -14/1943
Hartford.... -7/1967 - -9/1979 - -18/1943
Providence.. -5/1967 - -7/1979 - -14/1943
Worcester...-12/1967 - -11/1979 - -19/1943
Blue Hill...-10/1967 - -9/1979 - -18/1943

&&

Box watches/warnings/advisories...
CT...wind chill warning from 4 PM this afternoon to noon EST Sunday
for ctz002>004.
Massachusetts...Wind Chill Advisory from 6 PM this evening to noon EST Sunday
for maz022>024.
Wind chill warning from 4 PM this afternoon to noon EST Sunday
for maz002>019-026.
Wind chill warning from 1 PM this afternoon to noon EST Sunday
for maz020-021.
Rhode Island...Wind Chill Advisory from 6 PM this evening to noon EST Sunday
for riz008.
Wind chill warning from 4 PM this afternoon to noon EST Sunday
for riz001>004.
Wind chill warning from 1 PM this afternoon to noon EST Sunday
for riz005>007.
Marine...heavy freezing spray warning from 4 PM this afternoon to 10 am
EST Sunday for anz231>235-237-250-251-254>256.
Gale Warning from 11 am this morning to 10 am EST Sunday for
anz231>235-237-250-251-254>256.
Gale Warning from 11 am this morning to 7 am EST Sunday for
anz230-236.

&&

$$
Synopsis...Frank/doody
near term...Frank/doody
short term...Frank
long term...doody
aviation...Frank/doody
marine...Frank/doody
climate...

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