BOX issues Area Forecast Discussion (AFD) at Sep 21, 1:24 AM EDT
852
FXUS61 KBOX 210524
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
124 AM EDT Sun Sep 21 2025
.SYNOPSIS...
Cooler air this weekend will be followed by a warming trend
early next week. Our dry weather pattern also continues next
week, with the exception of some showers possible around the
middle of next week. Temperatures will also average above
normal next week, with Tuesday expected to be the warmest day;
temperatures may reach 80+ degrees at some locations.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Key Messages:
* Dry with light winds and elevated fire weather concerns over the
interior
* Good radiational cooling tonight, leading to lows in the upper
30s for the usually colder spots; 40s elsewhere
Not much change to the overall pattern with high pressure in
firm control. Light winds and relatively clear skies will lead
to good radiational cooling tonight. The only brakes on that car
preventing even lower temperatures will be the surface dew
points. Did favor the lowest temperature guidance.
We are also getting to that time of year where the coolish
nights result in some valley fog. Not thinking much frost
tonight across southern New England.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 AM MONDAY/...
Key Messages:
* Dry and cool weather continues into Sunday Night
High pressure moves slightly farther offshore Sunday into Sunday
night. This may permit some more clouds, but not any rainfall.
Still expecting rather light E to SE winds. Slightly below
normal temperatures anticipated.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Key Messages:
* Warmup expected early this week, highest temps on Tuesday
* Potential for some beneficial rainfall Tuesday into Wednesday
Guidance continues to paint an unsettled picture in the long
term as a longwave trough digs into the central CONUS by
midweek. Biggest forecast challenge will be pinning down the
movement of a surface front and multiple waves of low pressure
that guidance suggests track along it. Higher confidence in
increasing temperatures and humidity Monday and Tuesday.
NBM probs for high temperatures of 80F+ on Tuesday continue to
be elevated in the CT and Merrimack River Valleys. Guidance
shows 925 temperatures rising to between 19 and 21C by Tuesday
afternoon so with deep mixing, the aforementioned river valleys
shouldn't have too much trouble rising into the lower 80s. In
terms of moisture, ensembles have increased forecast PWAT values
from 1.4-1.6" to 1.6- 1.8". Another notable change amongst
deterministic models has been to trend the precipitation to be
more convective in nature. Guidance has increased forecast
SBCAPE values to between 1000 and 1500 J/kg, especially across
the interior. While severe weather probs remain low at the
moment, we could certainly see areas of locally heavier rainfall
and a few rumbles of thunder.
Upper level disturbance and surface cold front moves east of the
region Wednesday with upper level ridging and surface high
pressure making a return towards Thursday. Watching the
potential for another round of unsettled weather later in the
week as a large upper level low circulates over the central US
and the Midwest. At the moment, deterministic models are fairly
divided in terms of the western extent of appreciable rainfall
from this system. The Euro and CMC show a wetter, further west
solution while the GFS has minimal rainfall. Temperatures begin
to fall back into the 70s and upper 60s past Tuesday, averaging
out to be just above normal.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through 12z...High Confidence.
VFR. Calm/light and variable winds. Winds may take slightly
longer to decrease over the Islands, but should become less
than 10 knots. Patchy fog possible in low-lying areas,
especially the CT River Valley.
Sunday...High Confidence.
VFR. Winds becoming E to SE through the day at 10 knots or
lower (slightly higher than 10 knots over the Islands).
Sunday Night...High Confidence.
VFR with some patchy MVFR/IFR over parts of the interior from
patchy fog/lower ceilings. Light and variable to S winds away
from the coasts. Light E winds towards the coastal waters.
Monday...High Confidence.
VFR. Primarily S winds less than 10 kts.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...High confidence in TAF.
Outlook /Monday Night through Thursday/...
Monday Night: VFR.
Tuesday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA, slight chance TSRA.
Tuesday Night: VFR. Chance SHRA, slight chance TSRA.
Wednesday: Mainly VFR, with local IFR possible. Chance SHRA.
Wednesday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.
Thursday: VFR. Slight chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Sunday Night...High Confidence.
Rather light S to SE winds and seas during this time. Good
visibility.
Outlook /Monday through Thursday/...
Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Monday Night: Winds less than 25 kt. Seas up to 5 ft.
Tuesday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain showers.
Tuesday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers, slight chance of thunderstorms.
Wednesday through Wednesday Night: Winds less than 25 kt. Areas
of seas approaching 5 ft. Chance of rain showers.
Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Belk/FT
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...FT
AVIATION...Belk/Hrencecin/FT
MARINE...Belk/FT
Source: BOX issues Area Forecast Discussion (AFD) at Sep 21, 1:24 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202509210524-KBOX-FXUS61-AFDBOX)
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