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Area forecast discussion
National Weather Service Taunton Massachusetts
1044 PM EST Thu Jan 18 2018

Synopsis...
dry and seasonably cold conditions into Friday, then a warming
trend this weekend with continued dry weather. A storm system
will affect the region sometime late Monday into Tuesday with
mostly rain and coastal wind, but there is a risk of some wintry
mix/ice across the interior. Warm weather Tuesday is replaced
by blustery, dry and seasonably cold weather Wednesday and
Thursday.

&&

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

1020 PM update...

Still noting low clouds lingering along east coastal areas
including Cape Cod and the islands as intensifying low pres
continues to move offshore. Another area of low clouds will push
across central and northern portions of the CT valley as seen
on GOES-16 nighttime microphysics channel as well as hourly
obs. This area is associated with quickly passing 500 mb short wave
in the fast northern stream flow aloft, then should lift
further into northern New England overnight. Will watch this
closely, as short range models showing this feature pushing a
bit further S than previous forecast runs. Noting northwest wind gusts
across the nearshore waters at 15-20 kt.

Overall forecast in pretty good shape but did refresh to bring
near term conditions current. Temps were a couple of degrees
either side of forecast which were adjusted.

Previous discussion...

Deamplifying 500 mb impulse sweeping across the region overnight.
Accompanying ascent with differential vorticity advection and
parent jet streak. Overrunning response but atmosphere rather
void of moisture given precipitable waters up around 0.2
inches. Green's and white's likely to see some snow potentially
extending as far S as the Berkshires as flurries. Otherwise
scattered to broken cloud decks while monitoring low-level
stratus lingering along the high terrain and along the Outer
Cape. With clouds anticipated, leaning away from coldest of
guidance, that being met/mav.

&&

Short term /6 am Friday morning through Friday night/...

Friday...

Departing 500 mb vort Max with accompanying enhancement to the low-
level wind profile. Mixing out to around h9 through the day,
there's the possibility of some breezy west winds during the
morning, otherwise relaxing through the remainder of the day
beneath a follow-up brief, weak ridge of high pressure. Boundary
layer lapse rates remaining well mixed, beneath a dry inversion,
and anticipating temperatures to warm into the mid and upper 30s,
with snow melt, can't rule out some few to scattered pancake
cumulus.

Friday night...

Continued energy and moisture accelerating through the pseudo-
zonal flow, sagging S into the Great Lakes region. Up against
high pressure over the southeast conus, an amplified gradient wind
response with accompanying speed Max at h925. Warmer, dry air
pushing out of the SW, warming within h9-7 apparent within model
forecast soundings, limitations on mixing down to the surface.
Thus expecting a gradient wind response with strongest winds
potentially in excess of 30 mph along the S-coast, across the
cape and islands. Keep it dry but also mild with the winds. Lows
down in the 20s for most locations.

&&

Long term /Saturday through Thursday/...
340 PM update...

Highlights...

* dry and mild this weekend, possibly low 50s Saturday!

* Another storm will bring mostly rain and gusty coastal winds
late Mon into Tue with a risk of some interior mixed
precip/ice

This weekend...

Confluent flow aloft across New England provides dry weather to
the region this weekend. Low pres tracking across southeast
Canada combined with high pres over the southeast states yields
a tight westerly pgrad over the area. Warm air just above the
surface with 925 mb temps +2c to +4c. However model soundings
indicate a Stout subsidence inversion limiting blyr mixing. Thus
how much warm air aloft mixes down to the surface? Given the
tight westerly pgradient and associated downsloping
winds/adiabatic warming looks to be an overachieving temp setup.
Model 2-meter temps and MOS guid continue to trend warmer with
each run. European model (ecmwf) MOS and GFS MOS are the warmest guidance sources
and will lean in this direction. Thus will go warmer than guid
Sat with highs in the upper 40s to lower 50s, warmest in the
coastal plain of Rhode Island and southeast Massachusetts. Although cooler along the
immediate South Coast and islands given west-southwest winds coming off the
chilly near shore waters.

Regarding winds Sat, GFS model soundings suggest g35 kt
possible. Pgrad supports a windy so could see a few g40 mph but
gusts 15 to 30 mph more common. Another nice day Sunday however
winds will be much less along with temps not quite as mild,
45-50. Still 10-15 degs above normal. Turning colder Sunday
night as a backdoor front slips across the area as 1037 mb high
builds southeast into Ontario and Quebec.

Monday/Tuesday...

Pacific short wave marches across the country with an influx of
Gulf and Atlantic moisture as it approaches from the southwest
with pwats surging up to +2 South Dakota Tue morning across southern New
England. Fairly robust wind anomalies within this moisture plume
with gefs ensembles offering +2 South Dakota 850 mb and 925 mb winds.
European model (ecmwf) more amplified than the GFS but the gefs lends some
support toward the stronger European model (ecmwf). Thus will base this portion
of the forecast toward a European model (ecmwf)/gefs blend.

Meanwhile, shallow cold air bleeds southward into southern New
England Monday behind the backdoor cold front and 1038 mb high
pressure builds from Quebec into Maine and New Brunswick. This
will provide a cold air damming (cad) setup for especially
northern Massachusetts later Monday and possibly lingering into early Tue
morning. Thus potential for a period of mixed precip/ice across
this region.

Elsewhere expecting a chilly windswept rain Monday night into
Tue morning with increasing east-southeast winds off the cool near shore
waters ahead of a strong cold front and possible triple pt low.
European model (ecmwf) and GFS both have 925 mb southerly jet up to 65-70 kt
crossing southern New England Tue. In addition, it's aways out
but some of the deterministic guid has mid level lapse rates up
to 6-7c/km along and ahead of the frontal boundary. Thus could
be some elevated convection which would enhance the threats of
strong winds aloft reaching the surface and locally heavy rain.
Both ensembles and deterministic guid have 1+ of rainfall
possible. As for temps, possibly another 50+ day especially in
the coastal plain where warm sector has best chance of advancing
but also temps may jump into the 50s behind the front as Post
frontal winds scour out any leftover shallow cold air from Mon
night/Tue morning.

Wednesday/Thursday...

Post frontal airmass is colder with 850 mb temps around -8c on
both gefs and ecens ensembles, which is seasonably cool for this
time of year. So expecting highs at or slightly above normal.
Although it will probably feel a bit colder given gusty west-northwest Post
frontal winds. Dry weather expected Wed and Thu.

&&

Aviation /04z Friday through Tuesday/...
forecaster confidence levels...

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

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

Overnight...mainly VFR. MVFR ceilings will likely hang close to east
coastal MA, but impact the cape and islands with a more north/NE
onshore flow. Expect winds to become more northerly towards
daybreak Fri. Broken-overcast MVFR along the slopes of the Berkshires.
Otherwise mostly clear skies. West-northwest winds prevail.

Friday...
VFR. Brief period of breezy west winds as scattered-broken high clouds
erode. Few-scattered around 3500 ft possible during at times around
midday.

Friday night...
VFR. West winds on the increase towards Saturday morning. Mainly a
gradient wind with the potential of sustained values up to 25
kts, gusts up to 30 kts.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Saturday through Tuesday/...

Saturday: VFR. Windy with gusts to 30 kt.

Saturday night: VFR. Breezy.

Sunday through Sunday night: VFR.

Monday: MVFR/IFR conditions possible. Chance ra, chance sn,
freezing rain likely.

Monday night: mainly MVFR, with areas IFR possible. Breezy. Ra,
freezing rain likely, snow likely.

Tuesday: mainly MVFR, with local IFR possible. Breezy. Rain showers.

&&

Marine...
forecaster confidence levels...

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

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

1030 PM update...

Small craft advisories remain in effect over the open waters east
and S of Cape Cod and the southern outer waters. Winds gusting
to around 20 kt there with seas remaining around 5 ft.

Seas will hold at around 5 ft through the night, then should
subside briefly on Friday. Continued west winds through Friday.

Greater concern is on the Friday night into Saturday morning
period with increasing sustained winds potentially up to 25 kts,
gusts up to 30 kts. Small craft headlines may need to be
renewed. There is also a low risk of low end gales.

Outlook /Saturday through Tuesday/...

Saturday: low risk for gale force winds with gusts up to 35 kt.
Areas of rough seas.

Saturday night: low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas.

Sunday: winds less than 25 kt. Seas locally approaching 5 ft.

Sunday night: winds less than 25 kt.

Monday: winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain.

Monday night: low risk for Small Craft Advisory winds with
gusts up to 30 kt. Local rough seas. Rain likely.

Tuesday: moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 9 ft. Rain showers.

&&

Hydrology...

A Flood Warning remains in effect for the Connecticut River at
Middle Haddam, where ice jams are causing river fluctuations.

For details on specific area rivers, including observed and
forecast river stages, please visit the advanced hydrologic
prediction service (ahps) graphs on our website.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory for hazardous seas until 6 am EST Friday
for anz254>256.

&&

$$
Synopsis...nocera/sipprell
near term...evt/gaf

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