Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 281948
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
348 PM EDT Thu Mar 28 2024

.SYNOPSIS...

Rain will persist tonight with the heaviest across eastern
Massachusetts and Rhode Island. The rain will come to an end across
western Massachusetts and Connecticut after midnight...but persist
into Friday morning along the coastal plain perhaps even mixing with
wet snow before ending. Partial sunshine should develop away from
the Cape and Islands Friday afternoon. Sunny, but windy Saturday
with a chance for a few showers Saturday night. Mix of clouds
and sun on Sunday and Monday with near to above normal
temperatures. Very unsettled mid next week perhaps a few chances
for some accumulating snow!

&&

.NEAR TERM /THROUGH FRIDAY MORNING/...

345 PM Update...

Key Points into Friday morning...

* Rain persists through much of tonight...heaviest eastern MA
* Rain ends from west to east in most locations Fri morning
* Rain may briefly mix with snow before ending...but no impacts

Details...

The mid level trough axis coupled with a moist PWAT plume will allow
widespread rain to continue for most of the region. Our far western
zones...mainly the east slopes of the Berks to near the CT River
Valley are right on the sharp QPF/forcing cutoff so just periods of
spotty light rain are expected.

The upper trough will gradually shift east tonight as low pressure
off the mid-Atlantic coast lifts northeast and intensifies as it
passes east of the Benchmark Friday morning. This shifts the focus
of the heaviest rain/strongest forcing to central sections and
especially eastern New England. The Flood Watch continues overnight
for central and eastern New England...but this is mainly for River
and Small Stream flooding given all the rain we have had this month.

We do expect the rain to push east of western MA/CT not too long
after midnight...but the coastal low pressure system will keep rain
going along the coastal plain into Friday morning. The rain will be
heavy at times across eastern New England. As the coastal low
pressure system intensifies it will draw down colder air with it as
well. Some of the guidance indicates that some locations may briefly
mix with wet snow before the rain ends Friday morning in most
locations. However...raw model 2 meter guidance on the high
resolution guidance keeps temps a few degrees above freezing. So
thinking is that even if there is a bit of wet snow at the
end...no accumulations are expected. If somehow the models are
under- estimating the dynamic cooling process...there would be a
low risk for some very minor accumulations on grassy surfaces.
This is a fairly low probability at this point...but some wet
snow flakes may mix in at the end. Greatest risk might be in
eastern MA where the heaviest precipitation will linger into
Friday morning.

Overnight low temps will bottom out in the middle to upper 30s in
most locations by daybreak. North to northwest winds will increase
after midnight with some 20-25 mph gusts developing. In fact...by
Friday morning gusts may reach 30+ mph in some spots.

&&

.SHORT TERM /FRIDAY AFTERNOON & NIGHT/...

Key Messages Friday afternoon and night...

* Partial clearing Fri afternoon away from the Cape/Islands
* Windy Fri with highs in the upper 40s to the middle 50s
* Still quite breezy Fri night with lows in the 30s

Details...

Friday afternoon...

The intensifying coastal low pressure system will be headed north
towards the Canadian Maritimes Friday afternoon. The pressure
gradient will be increasing as a result...yielding windy conditions
especially Friday afternoon. Bufkit soundings indicate northwest
wind gusts of 25 to 35 mph with even a few gusts near 40 mph with a
modest LLJ. Partial sunshine will develop from west to east through
Friday afternoon away from the Cape/Islands. Rain may linger
into mid afternoon across parts of the Cape and Islands..but
ending there as well. Good mixing should allow for highs to
recover into the upper 40s to the middle 50s in most spots given
partial sunshine. Coolest of those readings will be in the high
terrain and especially the Cape/Islands where skies will remain
rather cloudy through the afternoon.

Friday night...

Sub 980 mb low pressure system lifts north through the Canadian
Maritimes Friday night. This will continue to result in quite breezy
conditions to persist with gusts in the 20 to 30 mph range and up to
35 mph or so in spots during the evening. Since the atmosphere will
not decouple...overnight low temps will only bottom out in the 30s.
However...Wind Chills will be in the 20s by daybreak Sat.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...

* Gusty winds persist into Saturday

* Chance for a spot shower Saturday night and Sunday but generally
  dry through Monday with near to slightly above normal temperatures

* Very unsettled mid week with the potential for two low pressure
  systems impacting the region Tuesday thru Thursday.


Saturday through Monday...

Low pressure stalls over the Gulf of Maine as ridge builds in from
the west, resulting in a rather tight pressure gradient and
northwest flow; which generally mixes quite efficiently in a drying
column. Fortunately, resulting 925mb LLJ appears to be about 10kt
weaker compared to this time yesterday, maxing out between 30-40kt
early Saturday, so while blustery conditions will persist into the
first half of the weekend, expecting max gusts in the 30 to 35kt
range across the highest terrain; below advisory level criteria.

As mentioned, the column dries with PWATS between 0.2-0.25" on
Saturday yielding sunny skies. Weak shortwave approaches from the
west Saturday evening, resulting in increasing cloud cover and
increasing moisture, as PWATs climb to ~0.8" across CT and RI
between 00-12Z. This shortwave may result in some light rain and
snow shower activity, particularly south of the I-90 corridor, but
current guidance shows the precip shield being "sheared apart" as it
dives south of the region. Overall, not expecting a high impact
event, but perhaps a couple hundredths of an inch of QPF will fall;
certainly not enough to snarl weekend plans.

Mid level ridging continues to build into SNE late Sunday and Monday
with decreasing cloud cover, particularly across eastern MA and RI.
Temps will rebound into the 50s, and perhaps mid 50s, on Monday.

Tuesday and Beyond...

The middle of next week looks quite unsettled with the potential for
not one but two low pressure systems to impact southern New England.
The first comes Tuesday and Wednesday as low pressure moves
northeast into SNE. With little to no time between the first and
second system, impacts will persist through the day Wednesday into
much of the day Thursday as a second low strengthens off the coast
of Maine Wednesday night. At present, temperatures look seasonably
cold, with highs in the 30s to near 40F, which could support mixed
precipitation or even snow north of the Route 2 corridor through the
period, acknowledging the forecast will rely heavily on the track of
the lows. In any case, with marginal temperatures, 10:1 snow maps
will far overestimate the potential for accumulating snow; with the
12Z Canadian`s 3 feet across north-central MA being completely out
of the question. With that said, ensemble probabilities and positive
snow depth change forecasts do paint a picture of accumulating snow
as far south as the MA/RI and MA/CT border over the 48 hour period.
Only time will tell if Boston sees more accumulating snow in the
month of April than March, oof!

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...

Forecast Confidence Levels:

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

18z TAF Update...

This afternoon & tonight...High Confidence.

IFR-LIFR conditions persist east of the CT River Valley well
into the overnight hours with widespread rain. Mainly IFR to
low end MVFR west of the CT River will improve to MVFR with even
VFR in spots after midnight and especially by daybreak.
Widespread rain with the heaviest across central & eastern
sections overnight. Rain may briefly mix with wet snow before it
ends from west to east in the 6z to 15z timeframe...but even if
that happens runways will remain wet. Light N winds shift to
mainly NNW and increase to between 10 and 15 knots with gusts of
20 to 25 knots developing after midnight.

Friday...High Confidence.

Lingering MVFR-IFR conditions Friday morning along the coastal
plain will improve to VFR in most spots by lunchtime...but
probably will take until mid-late afternoon for improvement to
VFR on the Cape and Islands. So in a nutshell...most locations
outside the Cape/Islands will be VFR by Friday afternoon. NW
wind gusts of 25 to 35 knots expected.

Friday night...High Confidence.

VFR. NW wind gusts of 20 to 30 knots persist with even a few
gusts up to 35 knots possible during the evening.

KBOS TAF...High confidence in trends, some uncertainty in exact
timing of details. Rain may briefly mix with some wet snow
09z-15z Fri before ending...but no accumulations expected.

KBDL TAF...High confidence in trends, some uncertainty in exact
timing of details.

Outlook /Saturday through Tuesday/...

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

Saturday Night: VFR. Breezy. Slight chance RA.

Sunday: VFR. Windy with gusts up to 30 kt.

Sunday Night: VFR. Windy with local gusts up to 30 kt.

Monday: VFR. Slight chance RA.

Monday Night: VFR. Chance RA.

Tuesday: Mainly MVFR, with local IFR possible. Breezy. RA
likely.

&&

.MARINE...
Forecaster Confidence Levels:

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

* NW Gales Friday/Fri night

Tonight through Friday night...High Confidence.

Low pressure off the mid-Atlantic coast will intensify as it moves
northeast passing east of the Benchmark Friday morning. As this low
pressure system intensifies...N winds will shift to the NW with
gusts of 30 to 35 knots by daybreak Friday. NW winds should gust up
to 35 knots through Friday night. We have gone with Gale Warnings
for most of our waters with strong small craft headlines for Boston
Harbor and Narragansett Bay.

Outlook /Saturday through Tuesday/...

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

Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain.

Sunday: Winds less than 25 kt.

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

Monday: Winds less than 25 kt.

Monday Night: Winds less than 25 kt. Chance of rain.

Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas locally approaching 5 ft. Rain likely.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch through late tonight for CTZ004.
MA...Flood Watch through late tonight for MAZ004>007-012>024-026.
RI...Flood Watch through late tonight for RIZ001>007.
MARINE...Small Craft Advisory from 4 AM Friday to 8 AM EDT Saturday for
     ANZ230-236.
     Gale Warning from 6 AM Friday to 11 AM EDT Saturday for ANZ231-
     250-251-254>256.
     Gale Warning from 8 AM Friday to 11 AM EDT Saturday for
     ANZ232>235-237.

&&

$$

SYNOPSIS...Frank/KS
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...KS
AVIATION...Frank/KS
MARINE...Frank/KS


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