BOX issues Area Forecast Discussion (AFD) at Mar 13, 7:27 AM EDT
306
FXUS61 KBOX 131127
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
727 AM EDT Thu Mar 13 2025
.SYNOPSIS...
Seasonably cool today. Trending milder Friday into this weekend,
especially away from the south coast. Sunday is looking windy
with above normal temperatures. A period of heavy rain and
potentially strong to damaging southerly wind gusts are
possible Sunday night into Monday. Drier weather returns by
Tuesday, with relatively mild temperatures.
&&
.NEAR TERM /THROUGH TONIGHT/...
A sheared mid level shortwave moves offshore early this morning,
taking the last of the showers across southern New England with
it. Dew point depressions shrank dramatically after midnight,
increasing the chances for some light showers to finally reach
the ground before daybreak. Not expecting much accumulation on
paved surfaces.
Otherwise, high pressure moves east across northern New England
into the Maritimes today. This places our region on the
periphery, with enough subsidence to maintain dry conditions,
but not quite enough to completely clear out our clouds. Onshore
easterly flow should continue. Expecting high temperatures to be
near to slightly above normal for mid March.
&&
.SHORT TERM /FRIDAY/...
Weak high pressure across southern New England should be just
strong enough to shunt a weak low pressure to our south. With no
strong forcing, not expecting the weather pattern to change
much. East to northeast winds continue into Friday with periods
of clouds overnight. Clearing from west to east Friday
afternoon. Temperatures trending above normal into Friday.
Mainly dry, but cannot rule out a stray shower or two towards
Nantucket tonight as this weak low pressure passes by.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Key Messages:
* Unseasonably mild Saturday and Sunday
* Heavy rain and strong to damaging winds possible Sunday
evening into Monday
* Drying out Tuesday, calmer conditions going into Wednesday
Details...
Ridging persists over the region for Friday night into Saturday
while a potent upper level trough digs through the Plains and
continues its progression eastward. Southerly flow advects in
warmer air that will bring temperatures to unseasonably mild
values for both Saturday and Sunday. Ensemble probabilities
remain high for highs over 60F Sunday over urban centers and
quite low for Saturday. However, highs Saturday are still
expected to be in the upper 50s, and some spots could hit the
60F mark. A significant LLJ also moves over the region Sunday
that when diurnal mixing kicks in could lead to some strong to
damaging wind gusts across southern New England. Ensemble
guidance has continued to indicate a 60 to 75 kt LLJ. Winds at
this speed will likely not reach the surface, but gusts to
45 mph over the higher terrain are possible, with most other
parts of the region (especially east of the I-95 corridor)
experiencing 35-40 mph gusts.
Aside from the winds, a period of heavy rain Sunday night into
Monday is expected. The shortwave energy associated with the
upper level trough moves into southern New England. Anomalously
strong southerly flow continues to advect significant moisture
into the region, elevating PWAT values. NAEFS guidance has PWAT
values at 1.25" and even higher across parts of CT into RI. In
terms of PWATs exceeding 1.25", ensemble probabilities of 50
percent and higher are prevalent in these same areas into SE MA
and the Cape within the timeframe for the heaviest rain in these
areas. Rainfall totals could be in the 1.5" to 2" range with
the GEPS and ECMWF ENS indicating a 20 percent chance that 24
hour rainfall may exceed 2" in CT, RI and parts of SE MA. The
GEFS, much like the deterministic GFS, continues to run slightly
drier than other guidance; probs for exceeding 2" over 24 hours
only reach around 10 to 15 percent for these areas. Another
thing to monitor with the possibility of this heavy rain is
snowmelt in some parts of southern New England, which may
encourage some river rises along the larger rivers of the
region.
Once this system exits the region, we dry out for Tuesday into
Wednesday as mid to upper level ridging builds back in behind
the shortwave. Winds will briefly shift to the WNW before
southerly flow returns with the ridging. Mild temperatures will
likely continue into Wednesday as a result.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Today...High Confidence.
VFR with E winds around 10 kt. Gusts to 20 kt possible along
the south coast, the Cape and the Islands, but the chance is low.
Tonight...High Confidence.
VFR for most with MVFR cigs possible for more eastern terminals
after midnight. Some IFR cigs over the Cape and Islands cannot
be ruled out. Winds remain around 3-7 kt overnight from the
east, shifting more NE in the early morning hours Friday.
Friday...High Confidence.
VFR with some MVFR to IFR towards the Cape and Islands. Light
winds starting from the E and NE then shifting more to the SE as
the day progresses, particularly over the interior terminals.
KBOS TAF...High Confidence in TAF.
KBDL TAF...High Confidence in TAF.
Outlook /Friday Night through Monday/...
Friday Night: Mainly VFR, with local IFR possible.
Saturday: Mainly VFR, with local IFR possible. Breezy. Slight
chance RA.
Saturday Night: Mainly VFR, with areas IFR possible. Breezy.
Slight chance RA.
Sunday: MVFR/IFR conditions possible. Windy with gusts up to
35 kt. Chance RA.
Sunday Night: Mainly MVFR, with areas IFR possible. Windy with
gusts up to 35 kt. RA.
Monday: Mainly VFR, with areas MVFR possible. Breezy. Chance
RA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Friday...High confidence.
High pressure passes by to the north of the waters today. A low
pressure passes by to the south of waters tonight into Friday.
Marginally rough seas across the southern outer coastal waters,
so will continue the Small Craft Advisories into Friday. Decided
to cancel the advisory for the outer coastal waters east of
Boston. No longer expecting winds to be strong enough to
generate high enough wave heights.
Outlook /Friday Night through Monday/...
Friday Night: Winds less than 25 kt. Areas of seas approaching
5 ft.
Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain.
Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain.
Sunday: Low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 10 ft. Slight chance of rain.
Sunday Night: Strong winds with gusts up to 35 kt. Rough seas
up to 13 ft. Rain.
Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Rough seas up to 12 ft. Rain likely.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 PM EDT Friday for ANZ254-255.
Small Craft Advisory until 1 PM EDT Friday for ANZ256.
&&
$$
SYNOPSIS...Belk/Hrencecin
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...Hrencecin
AVIATION...Belk/Hrencecin
MARINE...Belk/Hrencecin
Source: BOX issues Area Forecast Discussion (AFD) at Mar 13, 7:27 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202503131127-KBOX-FXUS61-AFDBOX)
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