071
FXUS61 KBOX 010658
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
258 AM EDT Mon Sep 1 2025

.SYNOPSIS...
High pressure remains in control through at least Thursday, bringing
an extended stretch of dry weather and seasonable temperatures.
Turns more humid by Friday, with an approaching cold front
bringing showers and a chance of thunderstorms. Humid conditions
and risk for showers may linger into Saturday ahead of the cold
front, then cooler and drier weather returns next Sunday as the
front moves off the coast.

&&

.NEAR TERM /THROUGH TONIGHT/...
240 AM Update:

Key Messages:

* Filtered sunshine today with canopy of high clouds, but dry
  weather prevails.

* Northeast winds near the coast keep temps along the eastern MA
  coast in the low 70s, with mid/upper 70s inland.

Details:

Good morning and welcome to the first day of meteorological autumn!
The past few nights have felt a lot like early autumn, and current
conditions are similar to those past few nights with temps in the
40s to lower/mid 50s. Broad high pressure centered in southern
Ontario continues to supply a dry, low-PWAT airmass for most of New
England. Meanwhile, considerable upper level moisture was being
advected northward from a midlevel closed low over the Delmarva
Peninsula, permitting an increasing cirrus canopy into Southern New
England. This upper level low is forecast to progress northward and
northwestward into NY through tonight, but high pressure will
continue to dominate our weather.

All that said, we`ll see a continued increasing canopy of mid to
high clouds for today, but dry weather will continue. Northeast
breezes to around 10 mph near the coast (up to around 15 mph Cape
and Islands) can be expected today, with lighter northeast winds
inland, and that onshore flow probably starts pretty early today. It
may be a struggle for eastern MA/Cape and Islands to reach the low
70s with filtered sun and the onshore winds; otherwise further
inland, highs in the mid to mid/upper 70s will again be the rule.

For tonight, mid to high clouds will initially be in place, while
gradually moving northeast through midnight. The only real question
mark is if we can see patchy fog develop as northeast winds ease and
better radiational cooling takes place. Still think it ends up being
pretty patchy and we haven`t had that much in terms of coverage the
last few days; dewpoints are a touch higher due to the onshore flow
so there might be a little more fog/mist overnight but nothing
widespread. Lows mainly in the lower to mid 50s, with upper 50s Cape
and Islands and towards Greater Boston.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
240 AM Update:

Key Messages:

* Mostly clear with onshore flow and temps in the 70s Tue,
  cooler near the coast.

* Modest warming trend Wed with a light southwest wind and
  highs well into the 70s to low 80s.

Details:

Tuesday and Wednesday:

Tranquil weather in this period as high pressure still remains in
control. We`ll see another day of northeast winds on Tue, so
temperatures on Tue should be similar to those today, maybe a degree
or two milder. It`s borderline and looking at the last 24 hrs worth
of wave height guidance I don`t think one is necessary, but later
shifts could consider a rip current statement for Tue for the east-
facing beaches over the Outer Cape and Nantucket with seas on the
outer waters around 5 ft. Rip current risk is in the Moderate range
for these beaches. Clear skies and light winds again favors strong
radiational cooling with patchy fog in the river valleys with lows
in the upper 40s to mid 50s.

More subtle changes to the theme as we move into Wed, as high
pressure will slip to our southeast and allow for a southerly flow
to develop. This will bring warmer low level temps (850 mb temps
around +10 to +11C) and mixed-out dewpoints in the mid 50s to near
60, so a touch more humid but still tolerable. But another high and
dry day with highs well into the 70s, with a few lower 80s in the CT
and Merrimack Valleys.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Key Messages:

* Warm and dry Thurs with temps mid 70s to lower 80s.

* A bit more humid on Fri as a frontal system moves through with
  showers and thunderstorms late Fri into early Sat.

* Still rather mild and somewhat humid Sat but becoming cooler
  than normal for Sun and Mon.

Details:

High pressure still is maintained early Thurs but weakens through
the day with increasing clouds ahead of a rather potent frontal
system. So we`ll have one more dry day on Thurs before this frontal
system moves through Southern New England on Fri. Rising humidity
levels on Fri as dewpoints climb into the mid 60s; this added
moisture combined with glancing QG dynamics favors wetting rains.
EPS Ensemble 24 hr rains probs show solid (40 to 60%) probs of rains
at or over a tenth of an inch, and lower (20-30%) probs of 24 hr
rains over a half-inch. It looks like the best chance is over the
interior higher terrain and less the further southeast one goes.

While the frontal systems clears our area on Sat with some residual
light showers over eastern New England, it looks like the post-
frontal airmass will be slower to cool off. Thus may have another
day of highs in the lower 80s with some humidity, before cooling off
toward more seasonable levels for Sun and Mon.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

06z TAF Update:

Through Today: High confidence.

VFR, just an increasing canopy of mid/high clouds. Winds become
NE around 5-10 kt, and around 10-15 kt near the
eastern/southeast coasts.

Tonight: High confidence, though moderate on patchy fog
coverage.

VFR. Patchy fog in at least the river valleys, but could also
develop at BED and near OWD. Light NE winds, calm at times.

Tuesday and Wednesday: High confidence.

VFR through this period. NE winds around 5-10 kt Tue, becoming
light Tue night, then becoming light SW on Wed.

KBOS TAF...High confidence in TAF. Winds become NE early (around
13-14z), but are expected to remain NE through the day.

KBDL TAF...High confidence in TAF.

Outlook /Wednesday Night through Friday/...

Wednesday Night: VFR.

Thursday: VFR. Breezy.

Thursday Night: Mainly VFR, with local MVFR possible. Breezy.
Chance SHRA, slight chance TSRA.

Friday: Mainly VFR, with local IFR possible. Breezy. Chance
SHRA, slight chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.

Overall high confidence.

NE winds increase today to around 10-15 kt, higher on the
southeast waters, which continue around 10-15 kt on Tue. Seas
will be slowly building on the southeast outer waters to around
5 ft by early Tue, which has prompted issuance of a small craft
advisory for Tue into 12z Wed for marginally high enough seas
for the waters off Nantucket and the Outer Cape.

Winds flip to SW around 10 kt on Wed, with seas less than 4 ft
all waters.

Outlook /Wednesday Night through Friday/...

Wednesday Night: Winds less than 25 kt. Seas locally
approaching 5 ft.

Thursday: Winds less than 25 kt.

Thursday Night: Winds less than 25 kt. Slight chance of rain
showers.

Friday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas locally approaching 5 ft. Chance of rain
showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 5 AM Tuesday to 8 AM EDT Wednesday
     for ANZ254-255.

&&

$$

SYNOPSIS...Loconto
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Loconto
AVIATION...Loconto
MARINE...Loconto