BOX issues Area Forecast Discussion (AFD) at Oct 1, 7:32 PM EDT560
FXUS61 KBOX 012332
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
732 PM EDT Thu Oct 1 2026
.WHAT HAS CHANGED...
A Small Craft Advisory has been issued for gusty prefrontal winds
and elevated seas across the southern waters Friday into Friday
evening. Also introduced a low chance for an isolated thunderstorm
Friday afternoon/evening as a cold front pushes through southern New
England. Otherwise, there were no significant changes to the
forecast.
&&
.KEY MESSAGES...
- Late taste of summer Friday with highs around 80, followed by
showers and a few thunderstorms Friday night.
- Cooler and drier Saturday, followed by a chilly Saturday
night.
- Watching if a wave of low pressure tracks far enough north to
bring a period of showers sometime Sun into Sun night.
- Coolest air of the season works into the region Mon night-Wed.
Areas of frost expected Tue night/early Wed AM. Dry weather
for most if not all of the next work week.
&&
.DISCUSSION...
KEY MESSAGE 1...Late taste of summer Friday with highs around 80,
followed by showers and a few thunderstorms Friday night.
Mid-level flow remains generally zonal through Friday, while high
pressure remains anchored off the coast of the Carolinas, returning
the low-level flow out of the southwest.
Still a bit cloudy tonight with mild temperatures, as lows only fall
into the 60s. Brief clearing develops Friday, allowing temperatures
to quickly warm. 925mb temperatures rise to +20C to +23C Friday
afternoon, supporting highs in the lower 80s for much of the region.
Dewpoints also climb into the 60s, providing a late taste of summer
for the second day of October. For perspective, this falls near the
climatological last 80 degree day of the year for Boston, which is
September 30th. Winds will also be elevated Friday with southwest
flow and mixing up to around 925mb, where winds aloft are 20-30
knots. Thus, gusts of 20 to 25 mph are not unreasonable during the
afternoon.
High pressure drifts east as a cold front approaches from the west
late Friday into Friday evening. Timing-wise, the 12z high-res
guidance shows the cold front and associated showers/storms pushing
through from northwest to southeast between roughly 3/4 PM and 10/11
PM. Plenty of moisture accompanies the front, with PWATs nearing or
exceeding 2 inches, which is well outside of climatology for early
October. Given modest forcing along the front and lower values of
instability, with only a few hundred J/kg of CAPE, cannot rule out a
thunderstorm or two. Low-level lapse rates are fairly steep at 7-
8C/km, though mid-level lapse rates are less impressive around
5C/km. There could be a few stronger gusts with DCAPE values of 600-
800 J/kg, though currently feel sub-severe gusts are more probable
than severe gusts. In addition, locally heavy but brief downpours
are possible given the anomalously high PWATs.
KEY MESSAGE 2...Cooler and drier Saturday, followed by a chilly
Saturday night.
Behind the front, high pressure builds across the eastern Great
Lakes Saturday with the aforementioned cold front just offshore.
This may lead to a period of clouds and a few showers offshore early
Saturday. Otherwise, drier and cooler Saturday with 925mb
temperatures falling to around +10C, supporting highs generally in
the upper 60s to around 70 degrees. High pressure moves into
southern New England Saturday night into early Sunday, setting the
stage for good radiational cooling. Lows fall into the 40s for much
of the region, with the warmest readings in urban centers such as
Boston around 50F. The coldest locations, especially across the
higher terrain of western Massachusetts, could fall into the upper
30s.
KEY MESSAGE 3...Watching if a wave of low pressure tracks far
enough north to bring a period of showers sometime Sun into Sun
night.
There remains considerable disagreement on the northern extent of a
precipitation shield associated with a wave of low pressure on Sun-
Sun night. Seems like the majority of the 12z deterministic guidance
keeps the northern extent of the rain shield south of our
region...perhaps briefly flirting with the south coast.
However...the ECWMF as well as some individual GEFS/CMC ensemble
members are further north and indicate the potential for a period of
showers. Greatest risk for a period of showers seems to be south of
the MA turnpike...but it is too early to rule out some showers
reaching the NH border or on the flip side of the coin remaining
completely south of southern New England. Either way...not expecting
any significant impacts even if rain does impact part of our region
for a time Sun into Sun night. Given the uncertainty...mainly kept
pops in the chance levels for now with the highest of those near the
south coast. High temps should be in the 60s...but it could end up a
bit cooler depending on the northern extent of the rain shield.
KEY MESSAGE 4...Coolest air of the season works into the region
Mon night-Wed. Areas of frost expected Tue night/early Wed AM.
Dry weather for most if not all of the next work week.
A pleasant/seasonable day of weather is on tap for Mon with highs
well into the 60s...perhaps even flirting with 70 in a few spots.
However...it will be a bit breezy on Mon as a cold front crosses the
region. Low level moisture is lacking...so expecting mainly a dry
frontal passage or worst case being just a few brief showers. Either
way...the main impacts will be the coolest air of the fall season
working into southern New England Mon night through Wed. Highs may
struggle to break 60 on Tue along with a breezy northwest wind. High
pressure building overhead will allow for the coolest night of the
young fall season Tue night. Low temps by daybreak Wed should be
down into the 30s for many locations...perhaps flirting with the
freezing mark in some of the normally coolest outlying locations.
Frost is likely in many spots as well.
The large high pressure system shifts east of the region by Thu.
This should allow for a southwest flow of milder/seasonable
temperatures to return by Thu afternoon.
Dry weather should pretty much dominate most if not all of the
upcoming work week. There is little moisture/forcing to support
precipitation.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update...
Tonight...High confidence.
VFR with some mid level cloudiness especially the first half of
the night. S-SW winds generally 10 knots or less...But some LLWS
on the order of 30-40 knots with a modest LLJ.
Friday and Friday night...High confidence in trends but
moderate confidence in timing
VFR continues, but a cold front will be approaching between
18-00z and bring with it a risk for brief scattered showers,
possibly a rumble or two of thunder, but the exact timing is
still uncertain. A best estimate would be between 21-03z. SW
winds 7-15 knots with some gusts of 20-25 knots on Fri. Winds
shift to the NW Fri night behind the cold front generally at 5
to 10 knots.
Saturday...High confidence.
VFR. N winds becoming NE generally at speeds of 10 knots or
less.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...High confidence in TAF.
Outlook /Sunday through Tuesday/...
Sunday: VFR. Breezy. Slight chance SHRA.
Sunday Night: Mainly VFR, with local IFR possible. Chance SHRA.
Monday: VFR. Breezy. Slight chance SHRA.
Monday Night: VFR. Windy with local gusts up to 30 kt.
Tuesday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Sunday morning...High confidence.
Area of high pressure south of New England and off the coast of the
Carolinas will shift east as a cold front approaches the southern
New England coastal waters Friday evening. Ahead of the front,
southwest flow will bring gusts of 20-25 knots across the southern
nearshore waters, including Cape Cod Bay, with marginal seas of 5-6
feet across the southern outer waters. A few showers and an isolated
thunderstorm are possible with the frontal passage Friday evening.
High pressure briefly returns Saturday with tranquil boating
conditions.
Outlook /Sunday through Tuesday/...
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Chance of rain showers.
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.
Monday Night: Low risk for gale force winds with gusts up to
35 kt. Seas up to 5 ft.
Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Local rough seas.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 11 AM to 8 PM EDT Friday for
ANZ231>235-237.
Small Craft Advisory from 11 AM Friday to 2 AM EDT Saturday
for ANZ254>256.
&&
$$
DISCUSSION...Dooley/Frank
AVIATION...Frank
MARINE...Dooley/Frank
Source:
BOX issues Area Forecast Discussion (AFD) at Oct 1, 7:32 PM EDT----------------
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