BOX issues Area Forecast Discussion (AFD) at Sep 25, 12:41 PM EDT086
FXUS61 KBOX 251641
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1241 PM EDT Thu Sep 25 2025
.SYNOPSIS...
Widespread showers and a few thunderstorms are expected into this
evening as a frontal system moves into the region. Locally heavy
rainfall may produce street flooding, and can't rule out an isolated
strong to severe storm in western New Eng. Improving conditions
Friday with increasing sunshine and warm conditions. The weather
pattern is mostly dry this weekend into next week, but watching
showers to the south may impact the region Saturday night into
Sunday. Mostly warm conditions expected into early next week, then a
strong cold front will deliver a fall airmass by next Wednesday
with temperatures well below normal.
&&
.NEAR TERM /THROUGH TONIGHT/...
1050 AM Update:
Key Messages:
* Stay weather aware through this evening.
* Low risk of additional urban flash flooding.
* Continued low risk of severe weather, including a tornado,
mainly across western MA/CT.
No significant changes from our thinking earlier this morning.
Heaviest rainfall that prompted Flash Flood Warnings in RI and
SE MA this morning was moving offshore and we are starting to
see showers/storms initiate to our west across PA/NY, while more
hit/miss type activity forms in the humid airmass in place
across SNE.
Front is located near South Coast and will make slow progress
northward through afternoon, which will allow airmass to
destabilize in warm sector, especially in western MA/CT where
there is strong model consensus on more widespread
showers/storms into the evening. Environment should feature
limited instability but decent shear so where storms are able to
develop we need to watch for localized wind damage or even a
tornado given sufficient low level helicity along with warm
front being nearby. This is reflected in tornado probs shown by
both Nadocast and CSU ML guidance.
We currently don't anticipate this being a widespread severe
weather event but certainly we may need to issue a few SVRs
(perhaps a TOR?) or FFWs.
&&
.SHORT TERM /FRIDAY/...
Key Messages:
* Improving conditions with increasing sunshine developing
* Warm and humid
Bulk of rainfall will be offshore by early Fri, but can't rule out a
few lingering showers across SE New Eng in the morning as weak front
moves through. Otherwise, expect improving conditions with clouds
giving way to increasing sunshine as drier air moves in from the
west. Mid level shortwave moves in from the west late in the day
which could trigger an isolated shower in the interior, but risk is
low. It will be a warm day as 925 mb temps are quite mild, 18-19C,
with W-NW flow developing. Highs should reach upper 70s to lower
80s. Dewpoints will be in the 60s so it will be a summer feel to the
airmass.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Key Messages:
* Above normal temps this weekend into Monday, then turning much
cooler by Wed with a touch of fall
* Dry for much of the period, but northern extent of tropical
moisture may bring a chance of showers Sat night into Sun
* Humberto expected to remain offshore next week
Warm and dry Sat, then will be watching tropical moisture plume lift
northward. GFS is most aggressive and bring a period of showers into
the region Sat night into Sun. Confluent flow is present over
northern New Eng so expect a sharp moisture gradient on the northern
edge which results in a low confidence forecast at this range. Based
on ensemble probs of 0.1" QPF, we have chance showers south of the
MA Pike Sat night into Sun. If showers do develop temps will be
several degrees cooler than current forecast with 60s, but 70s if it
remains dry. Warm weather continues into Monday with potential for
80+, then cold front pushes southward on Tue which will bring a fall
airmass by Wed as strong high pres builds to the north.
The strong front early next week should keep Humberto offshore.
Latest global ensemble tracks are in agreement that Humberto will
remain well to the south before curving offshore.
&&
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF Update: Low confidence due to uncertainty in timing.
Widespread IFR/LIFR in showers and fog through tonight. Main
area of concern for TS through the evening in western MA and CT
with much lower chances farther east. Slow improvement to MVFR
and eventually VFR Fri with VFR persisting into Fri night.
Winds veer to S through late afternoon and to SW and W tonight.
Strong 40-45 SW low level jet will cause LLWS most of tonight,
especially for coastal airports.
KBOS Terminal...Low confidence in TAF. IFR cigs should prevail
but there could be periods where cigs lift higher than forecast
through this evening, possibly to MVFR at times.
KBDL Terminal...Moderate confidence in TAF. Cigs could end up
being slightly higher than forecast, reaching MVFR at times
through tonight.
Outlook /Friday Night through Monday/...
Friday Night through Saturday: VFR.
Saturday Night through Sunday: VFR. Slight chance SHRA.
Sunday Night through Monday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Friday...Moderate Confidence.
As low level jet moves into the region, expect increasing S winds
this afternoon becoming SW this evening. Marginal gusts to 25 kt
possible across the waters with building seas to 5 ft over outer
waters. As a result we issued a SCA for this afternoon into tonight.
Winds and seas subside Fri. Expect poor vsbys into tonight with
showers and fog and a few embedded t-storms possible.
Outlook /Friday Night through Monday/...
Friday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers, patchy fog. Local visibility
1 to 3 nm.
Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Saturday: Winds less than 25 kt.
Saturday Night: Winds less than 25 kt. Chance of rain showers.
Sunday through Sunday Night: Winds less than 25 kt. Slight
chance of rain showers.
Monday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 2 AM EDT Friday for ANZ231-251.
Small Craft Advisory until 6 AM EDT Friday for ANZ232>234.
Small Craft Advisory until 8 AM EDT Friday for ANZ250-254.
Small Craft Advisory from 8 PM this evening to noon EDT Friday
for ANZ255-256.
&&
$$
SYNOPSIS...KJC
NEAR TERM...JWD
SHORT TERM...KJC
LONG TERM...KJC
AVIATION...JWD
MARINE...KJC
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 25, 12:41 PM EDT----------------
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