BOX issues Area Forecast Discussion (AFD) at Sep 30, 7:54 PM EDT
942
FXUS61 KBOX 302354
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
754 PM EDT Wed Sep 30 2026
.WHAT HAS CHANGED...
No significant changes.
&&
.KEY MESSAGES...
- Warm and pleasant stretch of weather arrives later this afternoon
through Friday evening.
- Next chance for showers arrives Friday evening along and ahead
of a rather strong cold front.
- Dry and seasonable this weekend, but with more clouds on Sunday.
- Much cooler autumn airmass settles over Southern New England early
to middle of next week.
&&
.DISCUSSION...
KEY MESSAGE 1...Warm and pleasant stretch of weather arrives later
this afternoon through Friday evening.
Still have high confidence in improving weather conditions this
afternoon through Friday as a mid-level ridge builds in over the
region. At present, lingering low clouds and drizzle persist across
eastern Massachusetts and Rhode Island. High res guidance shows this
stubborn low cloud/drizzle layer mixing out in the next several
hours and giving way to improving conditions. Could see some patchy
fog overnight in the interior given abundant moisture and weak winds
as the boundary layer decouples. Temps this afternoon will be quite
a bit warmer than they have been in recent days. Highs today rise
into the upper 60s to low 70s, then into the mid 70s and perhaps
lower 80s Thursday and Friday.
KEY MESSAGE 2...Next chance for showers arrives Friday evening along
and ahead of a rather strong cold front.
The next round of showers arrives after sunset Friday as a low
pressure system moves across Ontario and Quebec and a cold front
extends over the region. Guidance has trended later and weaker with
the precip with the highest POPs (30-50%) occurring after sunset
Friday. Regardless, not expecting much QPF out of this... less than
a quarter inch likely. Most guidance is showing the front stalling
out somewhere south of our waters,
Once the low moves through Quebec, a rather strong continental high
pressure system will build over Ontario, sinking those +4C to +6C
850mb temperatures down into New England and sharply dropping
surface temperatures through the weekend... overnight temps likely
drop into the upper 30s to low 40s and daytime highs in the mid
60s.
KEY MESSAGE 3...Dry and seasonable this weekend, but with more
clouds on Sunday.
Forecast outlook for this weekend now looks than it was looking 24
hours ago. The last couple cycles of deterministic and ensemble
guidance now conveys the idea that the strong high pressure which
builds in on Saturday remains strong enough through Sunday to
suppress rain showers lurching northward from the southern waters
away from land. Sunday still features a considerable amount of cloud
cover but dry weather looks to prevail, even as a pretty potent 500
mb shortwave in the northern stream treks eastward along the
US/Canada border Sunday night, draping a dry cold front southward
into the Sunday night/early Monday timeframe.
Saturday looks to be the pick of the weekend with mostly sunny skies
and highs in the mid to upper 60s, but lower 60s along the
eastern/southeast coast due to NEly onshore breezes. Highs Sunday
should be a couple degrees cooler with more cloud cover.
KEY MESSAGE 4...Much cooler autumn airmass settles over
Southern New England early to middle of next week.
Model guidance remains consistent on a dry, blustery and a much
cooler autumn airmass for early to mid next week. This occurs in
response to a strong upper trough establishing itself over the
Northeast, with a sfc 1030 mb anticyclone over the Gt Lakes settling
over New England by Tue night. Strong cold advection begins Monday
afternoon with 925 mb temps dropping to as low as -2C by 12z Tue!
Expect full sunshine and dry weather, but rather breezy on Monday
with a tight northwesterly pressure gradient, with highs in the low
to mid 60s and lows in the upper 30s to middle 40s. Even cooler
weather arrives by Tue, with highs only in the mid 50s. Depending on
how quickly winds slacken Tue night, some areas could have their
first frost since last Spring, with lows in the low to mid 30s
interior, upper 30s/mid 40s for the cities and low to mid 40s near
the eastern/southeast coast.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update:
Tonight: High confidence.
Mainly VFR. There is still a risk for patchy fog/mist at MVFR-
IFR levels across interior Southern New England airports, but
development is now more uncertain with a canopy of high clouds
much of the night. Light S winds through midnight, becoming SW
and increasing to around 5-8 kt.
Thursday: High confidence.
Multi-layered VFR decks. SW winds increase to around 8-12 kt
with gusts in the low 20s-kt range, perhaps mid 20s-kt range
over the Cape and Islands. Low level wind shear could develop
very late Thursday afternoon, but more likely after 00z Friday.
Thursday Night: High confidence.
Multi-layered VFR decks continue. SW winds decrease to around
5-10 kt, but SWly low-level jet of 35 kt could support low level
shear/turbulence for eastern TAFs.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...Moderate confidence in TAF. Fog development
overnight tonight is now more uncertain with canopy of high
clouds.
Outlook /Thursday Night through Monday/...
Friday through Friday Night: VFR. Breezy. Chance SHRA.
Saturday: VFR. Breezy.
Saturday Night through Sunday Night: VFR.
Monday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Overall high confidence.
Fairly tranquil conditions through Friday with light SW winds
and seas below 5 feet. Seas build towards 5 feet by late
Thursday/early Friday across the southern waters due to the
sustained southwest winds.
Outlook /Thursday Night through Monday/...
Friday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft.
Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers.
Saturday: Winds less than 25 kt. Seas up to 5 ft.
Saturday Night through Sunday: Winds less than 25 kt. Areas of
seas approaching 5 ft.
Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers.
Monday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
DISCUSSION...Loconto/FT
AVIATION...Loconto/Dooley/FT
MARINE...FT
Source: BOX issues Area Forecast Discussion (AFD) at Sep 30, 7:54 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202609302354-KBOX-FXUS61-AFDBOX)
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