BOX issues Area Forecast Discussion (AFD) at Sep 26, 2:26 PM EDT052
FXUS61 KBOX 261826
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
226 PM EDT Fri Sep 26 2025
.SYNOPSIS...
Mainly dry and warm today. Other than a risk of some showers late
Saturday night into Sunday morning, continued warm and dry weather
this weekend into early next week. Then a strong cold front will
deliver a fall airmass Wednesday and Thursday with much cooler
temperatures.
&&
.NEAR TERM /THROUGH TONIGHT/...
Key Messages:
* Mild and somewhat muggy this afternoon. An isolated shower across
interior possible, though it's a low probability, otherwise dry.
* Clear overnight, cool, and patchy radiational fog.
Enjoyable conditions for late September under a blend of clouds and
sun. Diurnal clouds are associated with a mid-level shortwave to the
northwest of southern New England. Cannot rule out an isolated rain
shower this afternoon driven by the lift from the higher terrain of
western and northern Massachusetts, a low probability, less than 20
percent.
After a mild afternoon, with highs in the middle to upper 70s, will
see temperatures fall overnight along with lowering dew points, as
drier air is advected into the region. High pressure builds tonight
with clear skies and light winds, should have good radiational
cooling and patchy areas of fog in prone locations. Overnight lows
fall into the 50s for the most part, coastal plain will have lows in
the mid-50s to 60F, while interior drop to the low 50s with coldest
spots in far northwest Massachusetts on either side of 50F.
&&
.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
Key Messages:
* Saturday is less humid, dry, but mild.
* Clouds overnight, mild, and showers possible. Best chance for the
showers will be at the immediate south coast.
Kicking off the first official weekend of autumn and it feels
more summer-like, not ideal for those seeking crisp fall
temperatures. But don't worry, that is coming up, more on that
in the long term discussion! For Saturday, weak high pressure
provides dry weather and 925mb temperatures between +14C to
+17C. BUFKIT soundings have limited mixing to 900mb, will be
able to tap into that warm layer and result in highs in the
mid-70s to 80F. A sea-breeze does develop, keeping coastal areas
a tad cooler. Clouds increase late in the day ahead of a surge
of sub-tropical moisture.
The potential for showers arrive near midnight through early hours
of Sunday morning. At this point, greatest confidence in rain on the
Islands, Cape Cod, coastal Rhode Islands/southeast Massachusetts. As
the previous forecast mentioned, confluent flow complicates matters
as there will likely be a sharp cut off for the northern edge of the
precipitation shield. Most of model guidance keeps the soaking
rains off shore, highlighting this are the HRRR, HREF (mean) &
NAM3KM with minor accumulations at the immediate south coast of
a few hundredths of an inch. Global deterministic are on board
with this assessment as well. The outlier is the NAM12km, which
kept wetting rains across Connecticut and Rhode Island. Kept
highest POPs (40 to 60 percent) to the immediate south coast as
a result and lower POPs the further inland. Clouds overnight,
temperatures are on either side of 60F.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
Key Messages:
* A few early showers possible Sunday morning across southeastern MA
* Above normal temps Sun through Tue, then turning much cooler Wed
through Friday
* Humberto will remain offshore next week, but will result in
increasing surf and rip currents Tue and especially Wed
Sunday through Tuesday
A few scattered showers possible early Sunday morning as a weak
area of low-pressure passes by the south coast of southern New
England. Latest guidance suggests areas along the south coast
and over The Cape/Islands would have the greatest chances for
precip, but overall only looking at slight chance PoPs in the
20-30 percent range. Elsewhere, expect a warm/sunny Sunday
afternoon with highs in the upper 70s to low 80s.
High pressure builds in from the west and continues to support
warm/dry weather through Tuesday with temperatures near or above
normal across southern New England both Monday and Tuesday.
Wednesday - Friday
On Wednesday, anti-cyclonic flow associated with a very large area
of high pressure over Canada will push a back door cold front over
southern New England from the northeast. This will result in a
substantially cooler temperatures than we're expecting during the
first half of the week with 925 hPa temps dropping to between 5 and
7 C. This will support high/low temperatures in the 60s and upper
30s/low 40s respectively through Friday. Expect dry conditions
through this period with high pressure generally suppressing any
potential for precipitation.
We will also be keeping a close eye on Hurricane Umberto, which at
this time may have the potential to bring high surf and dangerous
rip currents to southern New England next Wednesday and Thursday.
Details are vague at this time range, so stay tuned for further
details. Visit nhc.noaa.gov for the latest forecasts for
Umberto.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through 00z...
VFR. Blend of clouds, diurnal SCT to BKN Cu developed 030-050 across
interior of southern New England. Cu fades this evening. Winds are
west to northwest 8 to 12 knots, with infrequent gusts to 18 knots.
Overnight...High Confidence.
VFR, mainly clear skies will give way to patchy valley fog and IFR
conditions (~004) towards the second-half of the overnight. Low
confidence in extent of development, will mention a "FEW" group for
the prone terminals; ie KBED & KBAF. For now, will omit from KBDL.
Northwest winds are 5 to 10 knots, becoming calm.
Saturday and Saturday Night...High Confidence.
Mid-level VFR clouds (050-080) during the day, increasing low-level
clouds (015-030) for the south coast, Cape, and Islands during the
overnight, resulting in areas of MVFR ceilings. Sea-breeze possible
on Saturday for coastal terminals and a light south/southeast wind
overnight.
KBOS Terminal...High confidence.
VFR. Breezy wind W to NW 10 to 15 knots today, then overnight less
than 8 knots. Sea-breeze develops for Saturday.
KBDL Terminal...High confidence.
There is a low probability for fog to develop during the second-half
of the night, which could lead to a brief period of IFR condition
early Saturday morning.
Outlook /Sunday through Tuesday/...
Saturday Night: VFR. Slight chance SHRA.
Sunday through Tuesday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Friday through Saturday Night...High Confidence.
Cold front moves off shore today, shifting wind direction from the
southwest to the northwest during the first-half of the overnight. A
weak area of high pressure develops on Saturday and wind direction
becomes northeast to east/northeast. Throughout the forecast period
wind speeds are generally less than 10 knots, with gusts below 15
knots. Seas today are 3-4ft and lowering Saturday between 1-3 ft.
Mostly dry during this period, a few showers are possible across the
southern waters late Saturday night through early Sunday.
Outlook /Sunday through Tuesday/...
Saturday Night through Sunday: Winds less than 25 kt. Chance of
rain showers.
Sunday Night through Monday: Winds less than 25 kt.
Monday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Tuesday: Winds less than 25 kt. Local rough seas.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Dooley/RM
NEAR TERM...Dooley
SHORT TERM...Dooley
LONG TERM...RM
AVIATION...Dooley/RM
MARINE...Dooley/RM
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 26, 2:26 PM EDT----------------
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