Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 171946
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
346 PM EDT Sun Mar 17 2024

.SYNOPSIS...

Clear and cool tonight with steady west winds. Mainly sunny and
warm tomorrow with gusty west winds and elevated fire weather
concerns. Temperatures trending near to cooler than seasonable
for much of the upcoming week. Isolated showers possible each
day, especially Wednesday along with gusty winds. Dry by Friday
then uncertainty increases for when wet weather may return for
the weekend.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...

Tonight:

Winds turn WNW this evening as the low pressure over Quebec
continues to pull away to the east. Not expecting winds to go
completely calm overnight with 15-20 knot winds at 925mb and
some CAA promoting mixing. However, the 20-30 mph gusts from
this afternoon should diminish overnight. Even with clear skies,
steady winds should keep overnight lows from bottoming out,
only dropping into the low to mid 30s.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Key Points

* Elevated Fire Weather Concerns Tomorrow

* Gusty WNW Winds 20-30 mph

Tomorrow:

Upper level trough and associated cold pool aloft begins to
move into the region. With a strong WNW pressure gradient and
good boundary layer mixing up to 700mb, winds will become gusty
again up to 20-30 mph. High temps tomorrow should top out in
the low to mid 50s before colder air works in with the cold pool
aloft. Dewpoints tomorrow will be dropping into the teens which
will bring minRH values down below 30%. In collaboration with
our fire weather partners, we have opted to issue a SPS due to
elevated fire weather concerns for tomorrow afternoon in CT and
RI. There is a low chance for isolated pop up rain/snow showers
across western MA where the cold pool may be able to work in
before the loss of daytime heating. Otherwise mainly dry
tomorrow with diurnal cumulus in the afternoon again.

Tomorrow night:

The core of the 500mb cold pool works in overhead with temperatures
of -35 aloft. Strong CAA along with clear skies and diminishing winds
will allow for overnight temps to drop below freezing with mid to
upper 20s across the high terrain in northern MA. Any showers that
do form tomorrow afternoon will quickly come to an end with the loss
of daytime heating.


&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...

Key Points...

* Temperatures seasonable this week with highs in the 40s.
* Spotty showers possible Tue and more widespread on Wednesday,
  possibly lingering into Thursday for some; not a washout.
* Dry on Friday before another system may arrive next weekend but
  confidence is low.

The forecast remains largely unchanged from what we`ve been looking
at for the past few days, with the exception of continued
uncertainty as to how/when the pattern may break down for unsettled
weather next weekend. In the mean time we`ll be under the influence
of broad cyclonic flow aloft with a series of shortwaves rotating
through the base of the trough before brief ridging arrives for
Friday. This means generally cool and cloudy weather for much of the
week.

The first of these disturbances moves overhead on Tuesday bringing
increased cloudiness at least, given an anomalously cold airmass
overhead. This, with diurnal heating will lead to low level lapse
rates of 6-8C. This may be enough to overcome limited moisture in
order to produce some spotty rain or even graupel showers; best shot
is in the orographically favored high terrain of western MA. As the
previous forecaster mentioned, though, temperatures will be cooler
thanks to cold advection aloft and the well mixed boundary layer
will lead to drying of the airmass on breezy west winds. Thus,
dewpoints have been lowered into the teens and low 20s.

Wednesday is the best shot of any particular location seeing a rain
or snow shower as another shortwave and stronger surface low passes
to our north, but meager moisture and dynamics will keep this from
being a widespread precipitation event. One thing to note will be
the ramping up of the winds in the afternoon as the pressure
gradient tightens with the passage of the low, gusting 20-30 mph in
the afternoon. This is the start of the gusty winds, as Thursday
will be the windiest day. BUFKIT soundings indicate a very well
mixed boundary layer up to at least 850 mb where a 35-45kt LLJ
resides, mixing down gusts as high as 35 to 45 mph Thursday morning.
Winds will then decrease, but remain breezy all day. Friday will be
the quietest day of the week with a dry forecast and little wind
thanks to a transient high pressure. As for the weekend, we continue
to track a potential storm system around Saturday or Sunday, but the
GFS and ECMWF guidance remain in different camps as to the strength
and track of the low. For now have stuck to ensemble guidance
indicating increasing POPs starting Saturday.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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

Tonight...High Confidence.

VFR. W winds diminishing to 5-10 knots higher near the coasts.

Monday...High Confidence.

VFR. W winds increasing to between 10 and 15 knots. Should see
those gusts picking up to 20-25 kts by roughly 14-18Z

Monday Night: VFR. West winds diminish to 10-15 knots .

KBOS TAF...High confidence in TAF.

VFR, gusty WNW winds at 20-25 knots.

KBDL TAF...High confidence in TAF.

VFR, gusty WNW winds at 15-20 knots.

Outlook /Tuesday through Friday/...

Tuesday through Tuesday Night: VFR. Breezy.

Wednesday: VFR. Windy with local gusts up to 30 kt. Slight
chance RA.

Wednesday Night: VFR. Windy with gusts up to 30 kt. Slight
chance RA.

Thursday: VFR. Windy with gusts up to 35 kt.

Thursday Night: VFR. Windy with areas of gusts up to 30 kt.

Friday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight...

Decreasing westerly winds across the southern waters of 10
knots or less, while the northern waters could see continued
gusts of 15-25 knots. Seas slowly diminish to 3-4 feet, with
lingering 5 footers in the far outer waters.

Tomorrow...

Winds become gusty out of the west again at 15-25 knots. This
results in increasing sea back to 4-5 feet esspically for the
southern waters.

Tomorrow night.

Winds remain out the west, but continue to gust 10-20 knots.
Seas diminish to 3-4 feet.

Outlook /Tuesday through Friday/...

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

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Areas of seas approaching 5 ft. Slight chance of
rain.

Wednesday Night: Low risk for gale force winds with gusts up to
35 kt. Local rough seas. Slight chance of rain.

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

Thursday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Local rough seas.

Friday: Winds less than 25 kt. Seas locally approaching 5 ft.

&&

.FIRE WEATHER...
Monday and Tuesday...

There are some fire weather concerns for Monday and Tuesday. We
expect afternoon westerly wind gusts of 20 to 25 mph with
minimum relative humidity values between 20 to 30 percent Monday
and 25 to 35 percent Tuesday. Would not be surprised if RH
values ended up on the lower side of those numbers given very
dry air aloft. In coordination with our fire weather partners,
we opted to issue a SPS for CT and RI due to elevated fire
weather concerns Monday and possibly again on Tuesday.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 5 PM EDT this afternoon for ANZ230-
     231-236-251.
     Small Craft Advisory until 8 PM EDT this evening for
     ANZ232>235-237.
     Small Craft Advisory until 8 PM EDT Monday for ANZ250.
     Small Craft Advisory until 2 AM EDT Tuesday for ANZ254>256.

&&

$$

SYNOPSIS...BW/KP
NEAR TERM...KP
SHORT TERM...KP
LONG TERM...BW
AVIATION...BW/KP
MARINE...BW/KP
FIRE WEATHER...KP


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