BOX issues Area Forecast Discussion (AFD) at Sep 23, 7:44 AM EDT455
FXUS61 KBOX 231144
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
744 AM EDT Tue Sep 23 2025
.SYNOPSIS...
Warm and humid conditions today with scattered showers and a few
thunderstorms developing this afternoon into tonight as a front
moves into the region. Much cooler Wednesday with risk of showers
continuing, then another period of widespread showers and a few
thunderstorms Thursday into Thursday night as a frontal system moves
into the region. Unsettled weather pattern may linger into Friday,
then gradual improvement this weekend. Above normal temperatures and
increasing humidity return Thursday night into the weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
Key Messages:
* Warm and humid today with scattered afternoon showers and t-storms
developing in the interior
* More showers and a few t-storms moving across SNE tonight
Pre-frontal SW flow will bring a warm and increasingly humid airmass
into SNE today. Any morning stratus or patchy fog will quickly burn
off leading to partly to mostly sunny skies into early afternoon
before clouds increase from the north and west. 925 mb temps 18-20C
will support highs upper 70s to lower 80s away from the south coast.
This coupled with dewpoints climbing into the mid 60s will make it
feel like a summer day with warm and humid conditions.
There is a weak cold front which drops south into SNE this afternoon
which will serve as a focus for scattered showers and t-storms,
mainly in the interior after 2 pm. Instability is marginal with
CAPES 500-1000 J/kg and effective shear 25-30 kt across northern MA
so can't rule out an isolated strong storm with gusty wind but
severe probs are quite low. Locally heavy rainfall will be the
primary threat as PWATs increase to 1.75 inches. HREF indicating up
to 50 percent probs of greater than 1" QPF in 3 hours in northern MA
21-00z.
Threat for showers and t-storms will continue into the evening as
activity moves to the coast. The cold front is expected to stall
near the south coast tonight with plume of deep moisture persisting
across the region. Additional showers and a few t-storms will be
possible through the night as a shortwave moves into the region,
with activity eventually moving offshore toward daybreak as the
shortwave moves to the east with decreasing moisture. Given high
PWAT airmass, localized 1-2 inch rainfall amounts will be possible
through tonight, especially northern MA where highest 1 inch probs
are focused.
&&
.SHORT TERM /WEDNESDAY/...
Key Messages:
* Much cooler Wed. Risk for showers continues with low prob for
thunder across CT and SW MA
Cold front will settle south of New Eng as high pres builds south
from the Maritimes into the Gulf of Maine. This will set up a cool
and moist NE flow across SNE resulting in lots of low clouds. The
risk for showers will continue as additional shortwave energy
approaches from the west and there may be some drizzle also. There
is some marginal elevated instability across SW portion of SNE so
can't rule out a rumble of thunder from CT into SW MA. Temps will
remain nearly steady in the 60s, with some lower 70s possible from
Springfield to Hartford.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Key Messages:
* Another round of more widespread showers and a few thunderstorms
Thu into Thu night
* Warm weather Fri through the weekend, but unsettled Fri and
possibly Sat
Robust mid level trough moves slowly east from the Gt Lakes into New
Eng Thu into Fri. Ahead of the trough a modest low level jet will
advect anomalous moisture northward into New Eng with PWATs
increasing to near 2 inches. Increasing forcing for ascent acting on
this moisture will bring potential for widespread showers and a few
t-storms Thu into Thu night. The exact timing for best chance of
rainfall is uncertain but it will likely be sometime Thu into Thu
night assocd with low level jet Thu and approaching cold front and
shortwave Thu night. Also uncertain is when the showers exit but it
will likely linger into Fri as mid level trough is hanging back to
the west with additional shortwave energy moving through. There is
not much surface instability, but elevated instability increases
with the low level jet later Thu into Thu night so a few t-storms
are expected although severe threat appears low given lack of
instability. NBM indicating 40-60 percent probs of rainfall greater
than 1 inch Thu-Thu night and 15-30 percent probs for 2 inches.
Preliminary estimate is for 0.50 to 1.50 inches of rain which would
be much needed. It will become humid Thu and especially Thu night as
the elevated PWAT plume moves in. Expect dewpoints climbing well
into the 60s leading to a mild night Thu night and a warm and
humid day on Fri.
Looking ahead to next weekend, there is still uncertainty for Sat.
While deterministic guidance is dry, GEFS and EPS guidance still
showing moderate probs for light showers. But it is looking like a
warm day with above normal temps. Then next robust northern stream
shortwave tracks to the north on Sunday bringing a cold front
southward into the region. There is not much moisture so the front
may come through dry with warm conditions Sun and likely into
Mon as well with high pres in control.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF update...
Today...High confidence. Moderate for TSRA chances.
Any stratus/FG will burn off 12-14z with VFR for much of the
day. Scattered SHRA and isolated TSRA developing after 19z in
the interior. Brief heavy rain and lower cigs/vsbys with any
t-storms. SW wind 10-15 kt with gusts to 20 kt Cape/Islands.
Tonight and Wednesday...Moderate confidence.
Cigs lowering to MVFR-IFR tonight, LIFR possible after
midnight. Scattered showers and a few t-storms tonight. Chance
of showers or patchy drizzle Wed with MVFR/IFR cigs. Winds
shifting to light N tonight north of the south coast, with NE
wind 10-15 kt Wed.
KBOS Terminal...Moderate confidence in TAF. Low risk for TSRA
late afternoon and evening (22-01Z), but confidence not high
enough to include in TAF.
KBDL Terminal...Moderate confidence in TAF. Risk of t-storms
20-00z.
Outlook /Wednesday Night through Saturday/...
Wednesday: MVFR/IFR conditions possible. Chance SHRA.
Wednesday Night: MVFR/IFR conditions possible. SHRA likely.
Thursday: Mainly MVFR, with areas IFR possible. Breezy. SHRA
likely, slight chance TSRA.
Thursday Night: Mainly MVFR, with areas IFR possible. SHRA
likely, slight chance TSRA.
Friday: Mainly VFR, with local IFR possible. Chance SHRA.
Friday Night: VFR. Chance SHRA.
Saturday: VFR. Slight chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Wednesday...High Confidence.
SCA for outer waters into Wed for marginal seas. Winds expected
to remain below SCA. SW gusts to 20 kt today, then shifting to
E-NE 10- 20 kt Wed.
Outlook /Wednesday Night through Saturday/...
Wednesday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers.
Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Chance of rain showers.
Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Rain showers likely.
Thursday Night through Friday: Winds less than 25 kt. Seas
locally approaching 5 ft. Rain showers likely, slight chance of
thunderstorms.
Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers.
Saturday: Winds less than 25 kt. Chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from noon today to 2 AM EDT Wednesday for
ANZ235-237.
Small Craft Advisory until 8 PM EDT Wednesday for ANZ250.
Small Craft Advisory until 2 PM EDT Wednesday for ANZ254>256.
&&
$$
SYNOPSIS...KJC
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...KJC
AVIATION...KJC/Mensch
MARINE...KJC
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 23, 7:44 AM EDT----------------
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