FXUS61 KBOX 231946

Area Forecast Discussion
National Weather Service Boston/Norton MA
346 PM EDT Fri Mar 23 2018

A series of upper level disturbances impact the region over the
weekend with occasional rain and snow showers, but these will
be hit and miss. Conditions improve with high pressure on
Monday, then a warming trend is expected through the middle of
the week. The chance for rain then increases towards the end of
the next workweek.


Broad trough over the Northeast USA and Maritimes. One shortwave
from NY state sweeps through the trough tonight. This brings
cold advection aloft which brings vertical lapse rates of 6 to
6.5C/Km. Total-totals are forecast to reach 50 near NYC with 40s
over Southern New England.

Cross sections of RH show high values from surface to 700 mb.
This along with the decreased stability and increased lift
suggest lots of clouds and at least widely scattered showers in
Western Mass and Western CT where the southwave approaches.

Clouds will restrict cooling, especially where winds keep the
air stirred. Temperatures upstream early this morning were in
the 20s. Min temps tonight should be similar, although we will
show coastal lows around 30 or the low 30s due to effects of the


Upper trough remains over New England Saturday and Saturday
night. The shortwave moving through that trough moves off to the
east Saturday. But another shortwave from Hudsons Bay drops
south tonight and moves across New England Saturday and Saturday
night. A pocket of colder air aloft moves through with this
second trough, and moisture cross sections continue to show high
values to at least 700 mb. Lapse rates 925 to 700 mb are forecast
to reach 7C/KM. Lift will also be stronger, roughly 20 mb/hr
rather than the 10 mb/hr forecast for tonight. Best forcing
looks to be along/east of the Worcester Hills, covering Eastern
Mass and RI.

Considering all of this, we will bring chance pops to these
eastern areas and slight chance pops to Western Mass and
Northern CT. Temperature profiles favor light rain during the
day Saturday and snow for Saturday night. Snow accumulation
potential looks around an inch, possibly two inches in spots.
Best chance for accums would be over Northeast Mass, where the
forcing is strongest.

Mixing reaches to 850 mb with winds in that layer at about 15
knots and temperatures at the top of the layer -8C to -9C. Thus
expect north winds to gust 15-20 mph and max sfc temps in the
upper 30s to mid 40s.





Upper low centered over and to the east of southern New England
moves southeastward, while strong 1040 mb high centered over
Quebec shifts to the St. Lawrence River Valley to northern New
England. The high pressure keeps a low level NE onshore flow in
place over our area, which will keep temps well below seasonal
normals. Thinking highs will be in the mid 30s to around 40.

A tightening pressure gradient is expected as low pressure moves off
the Carolina coastline and tracks eastward. So expect some increase
in NE winds, with gusts up to 25-35 mph along E coastal areas as
well as on the islands. Models indicate a short wave rotating into
our area during the day. This should yield more clouds than sun and
isolated to scattered snow/rain showers. Looking at Bufkit model
soundings, the better chance for showery weather is over central and
eastern MA/northeast CT/RI, where onshore flow keeps low levels
moist. However further west into the CT Valley region of MA/CT, the
chance for measurable precipitation is diminished and hence it
should be drier there.

Sunday night through Monday night...

Cool Canadian high pressure sinks southward into New England,
yielding dry conditions with a continuation of somewhat below normal
temperatures thanks in part to a continued onshore breeze.
Quite dry air in place thanks in part to subsidence inversion,
so mostly clear/mostly sunny skies forecast for this timeframe.
The exception to this will probably be over the Cape and
Islands, where just enough low leve moisture may linger to keep
skies partly to mostly cloudy at least into Sunday night. Lows
in the 20s to around 30, and highs Monday in the mid 30s to mid


Models show mid level ridging and surface high pressure over our
area, yielding dry conditions with a warmup. This dry/warm region
narrows during Tuesday night, with a low pressure system passing
thru the Great Lakes Region, and an offshore low pressure
retrograding somewhat to the west. Thus we may see an increase in
clouds Tuesday night.

Wednesday through Friday...

Model spread brings uncertainties on timing of different features,
but overall expecting an increase in moisture with the potential for
rain and snow showers. For Wednesday low pressure lifting well
northeast of the Great Lakes Region, associated cold front may bring
showers to southern New England. However mid level ridging
could persist and keep the day dry. At this time limiting pops
slight chance.

During Thursday-Friday, mid level ridging is replaced with a broad
trough placing the east coastal US in SW flow. Should see an
increase in southern stream moisture heading out way as a low
pressure system moving towards and into our area, bringing a chance
for rain.


Forecaster Confidence Levels...

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

Short Term /through Saturday Night/...

Tonight...High confidence.

VFR, with ceilings 4000-6000 feet. Isolated rain/snow showers
with little/no effect on aviation conditions.

Saturday and Saturday night...High confidence.

VFR. Small potential for MVFR cigs/vsbys in rain showers
Saturday and snow showers Saturday night. North winds during the
day will turn out of the northeast later Saturday night.

KBOS Terminal. High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Sunday through Wednesday/...Moderate Confidence.

Sunday: Mainly VFR, with areas MVFR possible. Windy with gusts
to 30 kt. Slight chance SHSN.

Sunday Night: VFR. Windy with areas gusts to 30 kt.

Monday: VFR. Windy with local gusts to 30 kt.

Monday Night through Tuesday Night: VFR. Breezy.

Wednesday: Breezy. Slight chance SHRA.


Short Term /through Saturday Night/...High confidence.

Tonight...High confidence.

Quiet tonight with winds below 25 knots and seas below 5 feet.

Saturday...High confidence.

Quiet weather continues. Scattered rain showers in the
afternoon/evening may lower vsbys along the Eastern Mass

Saturday night...Moderate confidence.

A wind shift moves south across the waters after midnight. Snow
showers along this line may bring brief reductions in vsbys.
The wind shift will turn winds from the northeast and bring
building speeds. Gusts late at night will be between 25 and 30
knots. Seas will build after midnight, reaching heights of 5-7
feet on the eastern waters.

Outlook /Sunday through Wednesday/...Moderate Confidence.

Sunday: Low risk for gale force winds with gusts up to 35 kt.
Areas of rough seas. Slight chance of snow showers.

Sunday Night: Low risk for gale force winds with gusts up to
35 kt. Rough seas up to 12 ft.

Monday: Moderate risk for Small Craft Advisory winds with local
gusts up to 30 kt. Rough seas up to 11 ft.

Monday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 11 ft.

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 15 ft.

Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 15 ft.

Wednesday: Winds less than 25 kt. Rough seas up to 12 ft.


MARINE...Gale Watch from Sunday morning through Sunday evening for


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