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Area forecast discussion 
National Weather Service Taunton Massachusetts
403 PM EST Friday Feb 5 2016

Synopsis...
strong low pressure center offshore moves east of the region
allowing winds and snows to end this evening everywhere. Colder
weather follows tonight into tomorrow. High pressure brings dry
weather this weekend with above normal temperatures by Sunday. A
period or two of accumulating snow is likely Monday into Wednesday
especially across eastern Massachusetts...but its uncertain if this will
mainly be a nuisance event or a significant winter storm.



&&

Near term /until 6 am Saturday morning/...

*** warnings and advisories drop this evening ***
*** cold air will allow untreated surfaces to freeze overnight ***

Best f-general band around h6 coincident with heavy banded snow now
oriented over cape/islands. Ack was the final pin to fall into all
snow over the last hour. This feature continues to drop about 2-3
inch/hour snowfall rates along with areas to the west still
receiving around an inch/hour. Noting a stronger westerly
component to the flow thanks to stronger isallobaric winds with
the low pressure making its closest pass to the east. This is allowing
for more dry air to wedge into the lower levels. Its all ended for
areas west of Worcester and Tolland counties.

The snows will continue to push offshore and end from west-east over the
next 3-4 hours...possibly about 6 hours for ack. This suggests an
additional 1-4 inches of localized snowfall left for those still
receiving snow. The dry air is associated with very low surface dewpoints
in the teens...which will help allowing temperatures to cool with rapidly
clearing skies across the region through the evening. Will allow
the current warnings/advisories to continue. Including the Wind
Advisory for the cape and islands with very strong pressure change
couplet noted on msas/laps through the evening just offshore. This
will gradually end this evening though...with winds dying off at
the surface.

So...combining the clearing skies...ending snows and weakening
pressure gradient...good setup for rapid cooling overnight thanks to
dewpoints falling into the low teens. So a very cold night ahead
behind this storm. Given the very wet nature of the snowfall and
cleanup efforts today...untreated sfcs will likely become very
slippery overnight where the leftover breezes are unable to dry.
Patchy black ice possible. Will be issuing an Special Weather Statement for this risk
for the overnight hours. Expect mins mainly in the teens and low
20s.

&&

Short term /6 am Saturday morning through 6 PM Saturday/...
nose of high pressure builds over from the west. The combination of cold
advection aloft and slight increase in low-middle level moisture
suggests some afternoon cloud development...but little else.
Dropped highs a little bit from current forecasts as the added
snowpack will likely keep 2m temperatures a bit lower than some of the
guidance is currently suggesting. Expect highs mainly in the 30s.

&&

Long term /Saturday night through Thursday/...
highlights...

* dry with relatively mild temperatures sun
* period or two of accumulating snow likely Monday-Wednesday especially coast
* uncertain if Monday-Wednesday is nuisance snow or significant winter storm

Details...

Saturday night and Sunday...

Weak ridge of high pressure will result in dry weather. Low temperatures
Sat night mainly in the 20s...but some upper teens possible across
the normally colder outlying locations. Plenty of sunshine on
Sunday and westerly flow should allow much of the region to see
highs well into the 40s.

Late Sunday night through Wednesday...

Extremely complex and difficult forecast over this time period. A
couple of potent shortwaves will carve out a deep East Coast trough.
There is so much energy in the flow that the models are going to
have a tough time on resolving what exactly unfolds.

First thing is first...an initial shortwave will emerge off the
southeast coast and rapidly intensify as it moves northeast. Current
indications take the storm southeast of the benchmark. Now of
course that is 72+ hours out...so a track closer to the coast is
certainly possible and will need to be watched. However...even if
the storm passes well southeast of the benchmark...may still end up
with a light to moderate snow event especially on the coast. This
storm looks to have a fairly broad circulation with 35 to 50 knots
of east-northeast flow at 850 mb...so accumulating snow is likely for at least
the coastal plain. Also...some land/sea interface and ocean
enhancement may occur in eastern Massachusetts.

A second potent shortwave will drop down from the Great Lakes. This
will allow low pressure to develop off the middle Atlantic coast and
track northeast Tuesday into early Wednesday. A lot of what happens with this
system will be affected by the strength/track of the first system on
Monday. There are a wide range of possibilities...from a glancing
blow...to a strong noreaster and even an inverted trough setup.

To sum up...the main idea is that we are likely to receive at least
some snow at times Monday into Wednesday. Whether or not we see a
significant winter storm remains to be seen...but as mentioned in
the previous paragraphs all options are on The Table. We are likely
to see at least some accumulating snow especially along the coast.

Thursday and Friday...

Lots of uncertainty over this time frame. Will have to watch a wave
or two of low pressure that may end up bringing a bit more
snow...but much of this period may end up dry. Given low
confidence...will keep probability of precipitation at slight chance for now.

&&

Aviation /20z Friday through Wednesday/...
forecaster confidence levels...

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

Short term /through Saturday/...

Through 00z...high confidence in trends...timing may be off a bit.
Areas of LIFR/IFR in heavy snow and low ceilings continue through
about 20z everywhere...then give way to VFR from west-east through 00z.
Strong north winds with gusts 20-30 knots over the interior and 30-40 knots
along the Cape/Island.

Tonight...high confidence.
Mainly VFR. Any untreated and wet runways will freeze as
temperatures drop rapidly. Wind gusts remain north-northwest but diminish
through the overnight hours.

Tomorrow...high confidence.
Mainly VFR. Winds shift to the SW...but should remain around 10 knots
or less.

Kbos terminal...high confidence in trends...timing may be off a
bit.

Kbdl terminal...high confidence in trends....timing may be off a
bit.

Outlook /Saturday night through Wednesday/...

Saturday night and Sunday...high confidence in VFR conditions.

Monday through Wednesday...low confidence especially on timing.
Period or two of snow likely in this time frame...so will probably
see some IFR conditions especially along the coast on Monday. Northeast
wind gusts of 30 to 40 knots likely on Monday along the coast.

&&

Marine...
forecaster confidence levels...

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

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

Strong northerly winds will dissipate through the late evening
hours such that most gale warnings can be dropped by about
midnight. Small craft advisories will have to follow...because
even though winds will drop below thresholds...high seas of 10-12
feet have developed and will linger well into the day tomorrow.
So...expect Small Craft Advisory...mainly for hazardous seas to
follow.

Areas of snow/rain/fog reducing visibilities will come to an end between
6pm and 10pm local.

Outlook /Saturday night through Wednesday/...

Saturday night and Sunday...high confidence. Left over 5 foot swell
may linger into early Sunday morning across our eastern outer-
waters. Otherwise...winds/seas will be below Small Craft Advisory
thresholds with a weak ridge of high pressure in control.

Monday...moderate confidence. Gale force northeast wind gusts
likely as a rapidly deepening low pressure system likely tracks
southeast of the benchmark. There is a low probability for a period
of storm force wind gusts if that system tracks closer to the coast
than currently expected. Seas likely build to at least 15 feet
across our eastern outer-waters with long northeast fetch and good
mixing.

Tuesday and Wednesday...low confidence. At the very least northeast
small craft wind gusts and high seas will continue into Tuesday evening.
However...potential for stronger wind gusts depending on strength
and location of another low pressure system. By Wednesday wind
gusts and seas are quite uncertain...depending on what happens with
that second low pressure system.

&&

Tides/coastal flooding...
Monday...

There is a fairly high astro tide of 11.2 in Boston late Monday
morning. Northeast wind gusts of 30 to 40 knots from large
circulation of the intensifying ocean storm will likely result in a
1 to 1.5 surge. Seas should be built up to between 10 and 15 feet
by then...so feel there is a decent shot for pockets of minor
coastal flooding along eastern Massachusetts coast. There is a low risk for
pockets of moderate coastal flooding...if the storms ends up a bit
faster and tracking further west than current guidance indicates.

Monday night and Tuesday...

Main concern is if we end up with a second area of strong low
pressure tracking up the coast...which could impact additional high
tide cycles. Large spread in the guidance on whether or not this
happens. If so...will have to watch the Tuesday noon high tide
cycle across eastern Massachusetts as Boston has an 11.5 astro tide.

&&

Box watches/warnings/advisories...
CT...Winter Storm Warning until 5 PM EST this afternoon for ctz003-
004.
Massachusetts...Winter Weather Advisory until 6 PM EST this evening for maz022-
023.
Winter Storm Warning until 6 PM EST this evening for
maz019>021.
Winter Storm Warning until 5 PM EST this afternoon for
maz004>007-012>018-026.
Wind Advisory until 7 PM EST this evening for maz022>024.
Rhode Island...Winter Weather Advisory until 6 PM EST this evening for riz008.
Winter Storm Warning until 6 PM EST this evening for riz007.
Winter Storm Warning until 5 PM EST this afternoon for
riz001>006.
Marine...Gale Warning until 10 PM EST this evening for anz231>234-250-
254>256.
Small Craft Advisory until 4 am EST Saturday for anz230.
Small Craft Advisory until 10 PM EST this evening for anz236.
Gale Warning until 7 PM EST this evening for anz235-237.
Small Craft Advisory until 7 am EST Saturday for anz251.

&&

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

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