Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 140546

Area Forecast Discussion
National Weather Service Taunton MA
146 AM EDT Wed Mar 14 2018

The strong coastal storm will move to Nova Scotia late tonight and
into the Maritimes Wednesday. An upper level disturbance will bring
potential for snow showers and localized snow squalls Wednesday
afternoon and night. Otherwise, mostly dry weather with below normal
temperatures prevail into the weekend and early next week. Another
coastal storm may impact the region sometime next Tuesday or


10pm update...
Watching BUOY Obs and MSAS suggests the sfc low pres is
starting to fill and rising by a few hPa. This has led to rising
heights across interior New England and the implied subsidence
continues to yield dry spots and the bands continue to diminish
in intensity. Dry air will also continue to replace the moisture
in the DGZ with time. Still a couple of minor bands to watch,
one on the periphery of peak deformation as the upper lvl vortex
continues to rotate ESE from W NY. The other is more of a
weakened typical F-gen band across the E coast. Given these will
linger for a couple of hours, will hoist an SPS everywhere
through the early AM, and continue the Winter Storm Warnings for
NE MA, including the city of Boston through 06Z (2AM local).

Otherwise, timed POPs a little bit slower with this update to
account for the leftover light snows. Will highlight the risk
for a coating to a couple inches before things fully come to an
end, and lead into the SHSN/SHRA risk during the daylight hours

Will drop the High Wind Warning for ACK to a Wind Advisory as
gusts should be below criteria for warning from now on. Will
keep the advisory out through tomorrow evening however as
sustained winds and gusts will remain elevated through the day

Previous discussion...

The center of the strong storm system impacting our area will be
tracking away/northeastward tonight, moving to Nova Scotia.
Based on latest radar and surface observations, the snowfall
rates have diminished notably across western MA/CT. However a
sizable mesoscale band covered much of eastern MA and RI as of
430 pm, and this band will probably take a few more hours yet to
diminish/move east. Hence snowfall rates of 1- 2"/hr, possibly
3"/hr remain possible in that band in the short term. Headlines
continue as is, Blizzard Warning east coastal MA until 8 pm,
with NW wind gusts up to 50-60 mph. Winter Storm Warning until 8
pm for points west with gradually diminishing but still gusty
winds, with the exception of Nantucket.

High Wind Warning continues for Nantucket until 8 pm this evening,
with gusts up to 55-65 mph. Rain has been reported mixing in with
the snow at times, Nantucket`s precip should flip over to all snow
early this evening.

After 8 pm we should start to see a marked decrease in snowfall,
with the heavier snow bands ending/moving east. Generally have
chance pops for light snow south of the Mass Pike, with likely pops
for light snow lingering along/north of the Pike until around

While winds will continue to diminish after midnight, NW gusts of 30-
40 mph will remain possible over the Cape and Islands during the
overnight before picking up again on Wednesday.


During Wednesday while the coastal storm moves into the
Canadian Maritimes, southern New England continues to be in a
tight pressure gradient with the upper low situated overhead.
Moderately steep low level lapse rates indicate the potential
for scattered snow/rain showers, and W/WSW gusts of to 30 to 40
mph anticipated.

On the Cape and Islands stronger wind gusts of 40 to 50 mph are
possible and a Wind Advisory may be needed during the day.
Across the interior, especially the east slopes of the
Berkshires, scattered snow squalls are possible which could
produce a quick inch of snowfall where they track.



* Snow showers and localized squalls possible Wed night
* Mainly dry with below normal temps into early next week
* Watching another coastal storm for next Tue/Wed


High amplitude -NAO pattern will persist through the extended period
leading to a persistent mid level low across SE Canada and the
Maritimes. The result will be below normal temps through the period.
Dry weather is expected much of the time into early next week,
although can`t rule out a few rain/snow showers Thu/Fri as shortwave
energy swings through. A pattern shift to a +NAO phase expected
around the middle of next week. This transition may lead to yet
another coastal storm sometime next Tue/Wed.

Wednesday night into Friday...

Mid level low over SNE Wed evening will lift into the Maritimes
Thu/Fri as series of shortwaves move into the region. Expect lots of
clouds for much of the period but breaks of sunshine are likely at
times during the day.

Wednesday night could be interesting as scattered snow showers and
isolated squalls may impact the region given steep low level lapse
rates and sfc trough moving through. The WRF-NMM/ARW and 3km NAM all
suggest localized heavier squalls which have the potential to
produce localized accumulations of an inch or 2, especially interior
locations with a focus over the Berkshires as upslope snow spills
over into the east slopes. In fact, localized amounts up to 4 inches
possible across far western Franklin county.

Much of the day Thu/Fri should be dry, although still can`t rule out
a few snow showers especially higher terrain. Temps cooling to well
below normal by Fri as ensemble mean 850T drops to -12 to -14C.
Highs only upper 20s to mid 30s Fri. Blustery W/NW winds with gusts
to 30 mph at times Thu/Fri will make it feel much colder.

Saturday into Monday...

Mainly dry weather with below normal temps expected with NW flow
persisting. Some moderation Sunday ahead of a mid level shortwave
and cold front then colder again for Monday. Coldest days of the
period will be Saturday and Monday.


Complex set up with split flow pattern. Potent system moving out of
Plains with northern stream trough over the NE. Models indicate a
storm emerging off the mid Atlc coast but how far north it tracks
will depend on how quickly confluent flow over New Eng can lift to
the north. 12z guidance trended south but this is day 7-8 and spread
is high and confidence is low. Something worth watching.


Forecaster Confidence Levels...

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

Short Term /through Thursday/...High confidence.

Through 21Z today...
Mainly VFR. Occasional MVFR CIGS lingering early this morning,
but these too lift out. Some BKN-OVC MVFR CIGS mainly in the
Worcester Hills and Berkshires throughout the day, but VFR
dominates. Breezy with W winds 10-20 kt sustained and gusts
25-35 kt.

21Z Today Through 09Z Thu...
Mixed MVFR/VFR conditions in lower CIGS and brief SHSN. These
SHSN could lead to a localized snowfall 1-3inches along with
reductions in vsby to IFR/LIFR at times. These will be hit or
miss, so not all sites see these heavier SHSN.

09Z Thu through the rest of Thu...
Mainly VFR. Blustery conditions continue, but weaker winds
thank previous days.

KBOS Terminal...Mainly VFR until this evening during which a few
SHSN with brief heavy bursts of SN possible. This would yield
MVFR/IFR conditions at times. Otherwise, windy with gusts 25-30
kt at times through the day.

KBDL Terminal...High confidence in TAF. Occasional late
afternoon/evening SHSN.

Outlook /Thursday Night through Sunday/...

Wednesday Night: Mainly VFR, with areas MVFR possible. Windy
with gusts to 35 kt. Scattered SHSN. Localized +SHSN.

Thursday: Mainly VFR, with local MVFR possible. Windy with
gusts to 35 kt.

Thursday Night through Friday Night: VFR. Windy with local
gusts to 30 kt.

Saturday through Sunday: VFR. Breezy.


Forecaster Confidence Levels...

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

Short Term /through Thursday/...High confidence.

Storm Warnings continue into this evening for much of the waters,
with gusts of 50-60 kts possible on the outer southeast coastal
waters. Gale Warning in effect for Narragansett Bay thru 8 pm, then
Gale Warnings posted for Boston Harbor and BI/RI Sounds thru Wed.
After the storm force gusts subside, gale force winds will likely
persist thru Wed across much of the coastal waters.

Seas 15 to 25 feet to start across the outer Coastal Waters,
diminishing to 10-15 feet for Wednesday.

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

Wednesday Night: Moderate risk for gale force winds with gusts
up to 40 kt. Rough seas up to 14 ft. Scattered snow showers,
isolated rain showers.

Thursday: Low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 14 ft.

Thursday Night through Friday: Moderate risk for Small Craft
Advisory winds with local gusts up to 30 kt. Areas of rough

Friday Night: Strong winds with gusts up to 30 kt. Rough seas
up to 9 ft.

Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.

Saturday Night through Sunday: Winds less than 25 kt. Areas of
seas approaching 5 ft.


MA...Winter Storm Warning until 2 AM EDT early this morning for
     Wind Advisory until 5 PM EDT this afternoon for MAZ024.
MARINE...Gale Warning until 8 PM EDT this evening for ANZ231>235-237-
     Gale Warning until 6 PM EDT this evening for ANZ230.
     Small Craft Advisory until 8 PM EDT this evening for ANZ236.
     Gale Warning until 5 PM EDT this afternoon for ANZ254-255.


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