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

Synopsis...

Dry and seasonably cold conditions today and Friday, then a
warming trend this weekend with continued dry weather. A storm
system will affect the region sometime Monday night into Tuesday
with mostly rain and coastal wind, but there is a risk of some
mix/ice across the interior. Blustery and colder weather follows
next Wednesday.

&&

Near term /through tonight/...

1 PM update...

Storm digging off the mid-Atlantic coast, trowaling back along
290-300k isentropic surfaces but running up against subsidence,
drier air from the northwest as discerned from latest satellite, the
cloud shield eroding. But watching low level stratus off the
lakes and over the Gulf of Maine. Mesoscale processes occurring
as boundary layer mixes out, becoming trapped beneath the dry
subsidence inversion as discerned from 12z soundings from
Buffalo New York to Portland ME.

So the biggest forecast nuisance as of present: stratus decks
over the Berkshires, downsloping and eroding S/east with the northwest
flow, and marine stratus over the Gulf of Maine and Nantucket
clearly seen via satellite. Expecting the marine stratus to push
south-southeast with time while eroding, clipping the Outer Cape and Nantucket
with low cloud decks.

Otherwise high pressure in control well short wave over the southeast Continental U.S.
As energy continues to stream to our north over S Canada. Subsequent
westerly gradient lending to winds around 10 mph with gusts up
to 20 mph especially over the high terrain. Temperatures are
over-achieving where snow pack is less, warmer with highs in the
low to mid 30s. Colder to the north/west with deeper snow pack as well
as some scattered to broken cloud decks, highs upper 20s to low
30s.

Tonight...

Deamplifying 500 mb impulse sweeping across the region overnight.
Accompanying ascent with differential vorticity advection and
parent jet streak. Over-running response but atmosphere fairly
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 /Friday through Friday night/...

Friday...

Departing 500 mb vortmax 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 Wednesday/...

Highlights...

* dry and mild this weekend
* another storm will bring mostly rain and gusty coastal winds
Mon night/Tue with a risk of some interior mixed precip/ice

Mild and dry conditions expected this weekend under zonal flow
and rising heights. Temps should reach well into the 40s both
days with the chance of a few 50 degree readings Sat. It will
be a bit breezy Sat with potential for 25-35 mph SW gusts near
the coast which will temper the milder temps but less wind
Sunday.

Some light precip in the form of rain/snow showers possible Mon
in the developing warm advection pattern, but models have
trended a bit slower with timing of next storm, with greatest
impact likely sometime late Mon night into Tue. Deep mid level
trough/low approaching from the west is expected to lift NE
across the gt lakes and into southeast Canada. A robust pre-frontal low
level jet will likely bring a decent slug of rain to southern New England with
potential for heavy rainfall and strong coastal wind. Precipitable water and
low level wind anomalies are 2+ South Dakota which is pretty good for a
day 5-6 forecast. Exact timing of the rain and wind is uncertain
and there also remains enough uncertainty with thermal profile
that some interior mix/ice possible at the onset. European model (ecmwf) is more
robust with the colder air but it will take awhile for these
finer details to be resolved.

As storm exits, blustery and colder weather will likely follow
next Wednesday.

&&

Aviation /18z Thursday 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.

Rest of today into tonight...
VFR. Monitoring MVFR marine stratus over the Gulf of ME and
across ack. Anticipating low cigs to remain immediately off-
shore. West winds continue around 10 kts. Scattered-broken high clouds
towards evening, eroding into Friday morning.

Friday...
VFR. Brief period of breezy west winds as scattered-broken high clouds
erode. Few-scattered 035 possible during the day.

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 Monday/...

Saturday: VFR. Windy with gusts to 30 kt.

Saturday night: VFR. Breezy.

Sunday through Sunday night: VFR.

Monday: MVFR/IFR conditions possible. Chance 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.

Small craft advisories trimmed as west winds remain around 10 kts
which have allowed seas to diminish. Expect lower sea trends and
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.
Headlines may need to be renewed and there is a low risk of
gales.

Outlook /Saturday through Monday/...

Saturday: low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 11 ft.

Saturday night: low risk for Small Craft Advisory winds with
gusts up to 30 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.

&&

Hydrology...

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

Cold conditions will persist through Thursday which will limit
additional runoff. Continued ice jams will remain on some of the
rivers. There will be some increase of snow pack across
interior southern New England as well.

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...kjc/sipprell
near term...kjc/sipprell

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