Plum Island, Massachusetts Weather Forecast Discussion

926
FXUS61 KBOX 190721
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
321 AM EDT Fri Sep 19 2025
.SYNOPSIS...
High pressure will bring dry conditions today, but temperatures
will trend cooler for the weekend behind a cold front with more
autumn-like temperatures. The dry weather pattern continues
into next week with a notable warming trend. Low chance for some
showers sometime midweek.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Key Messages:
* Warm today with dry, breezy conditions
Generally, no major changes to the forecast for today. A cold front
from the north drops down across southern New England today,
bringing with it a drier airmass and NW winds. Guidance remains
supportive of mixing today that will bring down some breezier winds,
so an occasional gust from 20 to 25 mph is not out of the question.
Low relative humidities will also aid in elevating fire weather
conditions, though they will remain below Red Flag criteria. Despite
the cold frontal passage, the cold air behind it will lag and not
reach southern New England until tonight. Highs will be able to rise
once again into the upper 70s and low 80s as temperatures aloft
remain warm and mix down.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Key Messages:
* Cooler tonight through tomorrow with dry conditions continuing and
  winds decreasing Saturday
No significant changes to the forecast in this period. The colder
airmass to our north makes its way down to southern New England by
tonight. With it, high pressure starts to make its return, allowing
skies to clear and winds to calm. This will set the stage for
radiational cooling as lows across the interior dip into the low to
mid 40s. Dry air continues to sit over the region, so the chance for
any patchy fog is very low. Winds may remain around 5 to 10 mph
across the coastal areas, so radiational cooling there is not
expected to be as strong; lows there expected to be in the 50s and
upper 40s.
Winds continue to diminish for Saturday as high pressure builds over
New England and Ontario/Quebec with strong ridging aloft over the
Great Lakes. Skies remain clear and the colder airmass exerts its
influence; 925 mb temperatures settle just under 15C in the
afternoon. Highs Saturday may struggle to reach 70F for most
locations and remain in the 60s, though they may get just over 70F
in the CT River Valley. Dew points continue to fall into the 30s for
much of the interior and PWATs fall to values below 0.5" which may
lead to more fire weather concerns to start the weekend even with
lighter winds.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Key Messages:
* The dry pattern continues aside from a low chance for some showers
  midweek
Strong radiational cooling is expected for Saturday night with winds
going calm, conditions remaining dry, and skies staying clear. Lows
may approach the 30s for some spots, especially across NW MA. This
cooler air is expected to stick around through the weekend before a
warming trend kicks off at the start of next week.
Upper level ridging begins to weaken and move off to the east with
the associated surface high pressure doing the same to start next
week. A trough over the Great Lakes moves towards the region as the
high makes its exit. With high pressure shifting offshore, southerly
to southwesterly flow kicks in Monday into Tuesday, increasing
temperatures and moisture which may peak Tuesday according to
ensemble guidance. Ensemble probs for temperatures 80F+ remain
relatively high across much of eastern MA and the CT River Valley,
though they have trended down slightly over the past few runs (not
by much, but notable enough to hint at temperatures just reaching
80F rather than exceeding it). Ensembles are in good agreement in
mean PWAT values ranging between 1.4-1.5" across the region by
Tuesday afternoon, and deterministic and ensemble guidance hints at
some instability that could support rain showers. However, given the
extended dry weather we`ve seen, confidence remains low in these
showers materializing. And if they do, it`s not likely that they
provide the amount of rain we need for relief from these dry
conditions.
This disturbance moves east through midweek with high pressure
making a return towards Thursday and temperatures begin to fall back
into the 70s overall midweek.
&&
.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06Z TAF Update
Through Tonight...High Confidence.
No significant changes from the previous update. Lingering
MVFR/IFR cigs near Cape Cod and Islands will move offshore
leaving VFR conditions through tonight.
W/NW winds with gusts to 20kt today diminish and become N/NE by
this evening.
Saturday...High Confidence.
VFR. N winds go light and become more variable as the day goes
on.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...High confidence in TAF.
Outlook /Saturday Night through Tuesday/...
Saturday Night through Monday Night: VFR.
Tuesday: VFR. Breezy. Slight chance SHRA, slight chance TSRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Saturday...High Confidence.
Seas increasing to 4 ft for the northern outer waters tonight
after remaining around 3 ft or less through the day today.
Winds less than 25 kts today, though they increase this evening
approaching 25 kts for the northern outer waters after 00-06z.
Winds in other marine zones range 15-25 kts.
Winds decrease below 25 kts across all marine zones Saturday
afternoon/evening and seas fall to 3 ft or less as well.
Outlook /Saturday Night through Tuesday/...
Saturday Night through Sunday: Winds less than 25 kt.
Sunday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Monday through Monday Night: Winds less than 25 kt. Areas of
seas approaching 5 ft.
Tuesday: 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.
&&
$$
SYNOPSIS...Hrencecin/Mensch/JWD
NEAR TERM...Hrencecin
SHORT TERM...Hrencecin
LONG TERM...Hrencecin
AVIATION...Hrencecin
MARINE...Hrencecin

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