BOX issues Area Forecast Discussion (AFD) at Oct 20, 7:32 AM EDT293
FXUS61 KBOX 201132
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
732 AM EDT Mon Oct 20 2025
.SYNOPSIS...
A strong frontal system moves through the region this morning,
bringing a quick-moving line of heavy rain and strong winds.
The front moves offshore Monday afternoon with drying conditions and
continued breezy winds. Drier weather returns for Tuesday, but a
stronger cold front for Wednesday ushers in a cooler and unsettled
weather pattern for late in the workweek into Saturday.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Key Points
* Strong Frontal System moves through the region this morning
* Main impacts are heavy rain and isolated strong to damaging
wind gusts
The shortwave trough and strong frontal system are on our doorstep
and will be moving into the region shortly this morning. Warm
frontal showers have started to form ahead of the main line of
precipitation and will continue until the front is through. The
front is still anticipated to bring a Fine Line of heavy rain and
possibly a rumble or two of thunder. Guidance remains consistent on
timing, bringing it through the CT river valley between 6 - 8 am and
into the I-95 Corridor between 8 - 11 am, moving offshore between
noon - 2 pm. The primary hazard with the fine line will be a brief
period of heavy rain during the morning rush hour. Even with rain
rates likely exceeding 1 - 2 inches per hour, not anticipating flash
flooding due to the progressive nature of this system. Wind fields
aloft remain strong, at 40-50 knots even down to 2kft. Still a
great deal of uncertainty if the winds aloft will mix down inside
the fine line, as soundings indicate a subtle inversion and stable
layer from the surface to 2kft. HREF min wind gusts suggest 30-
40mph gusts are likely, with HREF max showing 40-60mph gusts are
possible. The probability for severe wind gusts does increase
further east as dual heating has a chance to mix out the nocturnal
inversion before the fine line reaches the east coast. Thunder
chances appear limited with the fine line, even with 200-400 J/kg of
MUCAPE. Most of that instability resides within the lowest 0-3km,
which will limit updraft strength above the freezing level.
Dry slot moving in behind the dry line will lead to rapidly drying
conditions for the afternoon. There could be a few spot showers
across NW MA as the core of the shortwave and cold pool aloft move
into the region. High temperatures stay mild today in the mid to
upper 60s with breezy southerly winds.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
* Dry and mild weather Tuesday
Tonight:
Upper-level shortwave begins to move north into northern New England
with rising height filling in behind. Skies begin to clear
overnight with subsidence aloft, but surface winds remain elevated
from the WSW at 10-15mph. This should keep overnight temps from
tanking into the 30s, instead staying in the 40s. With the residual
moisture from morning rains, there could be patchy ground fog in low-
lying areas.
Tomorrow:
The upper-level ridge will give us a 1-day break from the active
weather as another shortwave follows behind it for Wednesday. High
temperatures remain mild on Tuesday in the mid to upper 60s as winds
turn southerly in response to the approaching shortwave. Skies start
the day clear, but high clouds will begin to filter in by late
afternoon.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Key Messages:
* Rainy conditions with southerly breezes for Wed AM as a cold front
moves through.
* Cooler and more unsettled for late in the week into early weekend.
Details:
Another rather strong cold front moves in on Wed, and while there is
still some uncertainty on the timing of the front, guidance
continues to favor an earlier-in-the-day passage similar to the
frontal system for Mon (early AM to off the coast by early PM).
Winds don't look as strong as the Mon frontal system, and there
isn't as much moisture to work with either, so impacts could be
lesser than the frontal passage on Mon. Cloudy conditions with a
period of breezy/gusty showers again for Wed.
A cooler and unsettled weather pattern then establishes itself
across the Northeast underneath deep cyclonic flow aloft late this
week into the early part of the weekend. Expect partly cloudy
conditions for most, with partly/mostly cloudy conditions western
New England and temps running a couple degrees cooler than normal in
the 50s. Couldn't rule out a passing shower underneath some of the
stratocu at times but the vast majority of this period is dry.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF Update:
Today: High Confidence
CIGS will gradually drop to MVFR ahead of the frontal system
approaching for this morning. Said frontal system will bring a
round of heavy rain, strong winds in excess of 30-40 knots, and
IFR/LIFR CIGS. The line of SHRA has moved slightly faster than
initially forecast (as of 1125z, the line is about to be right
over ORH), so the biggest change was pushing up the time for
SHRA about an hour or so for terminals east of BDL. Confidence
remains very low for the chance of TSRA this morning, as there
ended up being none over BDL when the line passed through. And
as of the time of writing this discussion, there has not been
any TS reported. Opted to keep it out of the TAF for all sites
this morning and stuck with SHRA.
CIGS behind the front are a bit more uncertain, but will
generally be a high end MVFR to low end VFR with breezy SSW
winds up to 25 knots.
Tonight: High Confidence
VFR. WSW winds at 10 to 15 knots. Some wind shear at 2kft
around 30 knots from the west.
Tuesday: High Confidence
VFR. Decreasing southerly winds.
KBOS Terminal...High confidence
VFR CIGS will gradually become MVFR this morning ahead of the
front. The heavy rain is anticipated to arrive around 16z with
IFR/LIFR CIGS and strong winds gusting 35-40 knots. After the
heavy rain moves out, CIGS should rebound quickly to around the
VFR/MVFR line. Winds behind the front remain gusty from the S
at 15-20 knots. Low confidence in TSRA this morning.
KBDL Terminal...High confidence
Rain and IFR cigs continue this morning, but should exit around
15z. After the heavy rain moves out, CIGS should rebound
quickly to around the VFR/MVFR line. Winds behind the front
remain gusty from the S at 15-20 knots.
Outlook /Tuesday Night through Friday/...
Tuesday Night: Mainly VFR, with areas MVFR possible. Breezy.
SHRA likely.
Wednesday: Mainly VFR, with areas MVFR possible. Breezy. Chance
SHRA.
Wednesday Night through Thursday: VFR. Breezy. Slight chance
SHRA.
Thursday Night: VFR. Slight chance SHRA.
Friday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Monday Night...High confidence.
Key Messages:
* Dangerous Marine conditions expected Monday morning to early
afternoon
* Short period of heavy rain with potential for gale to storm
force winds possible.
Dangerous marine conditions are expected this morning, and a strong
frontal system will bring a line of heavy rain and a brief period of
gale to storm force winds. Seas quickly rise to 4-8 feet this
morning with strong winds. Winds begin turning WSW behind the
front, with gusts up to 30 knots lasting through about midnight,
before decreasing to 20 knots by Tuesday morning. Winds turn more
SSW on Tuesday, but remain gusty around 20-25 knots. Seas gradually
diminish to 3-5 feet on Tuesday.
Outlook /Tuesday Night through Friday/...
Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Rain showers likely.
Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft. Rain showers likely.
Wednesday Night: Winds less than 25 kt. Local rough seas.
Chance of rain showers.
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas. Chance of rain showers.
Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Chance of rain showers.
Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
&&
.TIDES/COASTAL FLOODING...
330 AM Update:
South-southeast winds will increase this morning along the
southern and eastern coasts. We are most concerned for the
southern coast with this mornings high tide around 8 AM. At Fox
Point/Providence, the astro tide is around 5 ft MLLW. Storm
surge values early Sunday morning were as high as 1.5 ft at Fox
Point/Providence, and it stands to reason that as southeast
winds increase, storm surge values could reach 1.5 to 2 ft
range along portions of the southern coastline.
Though splashover with limited overall impact is the most likely
outcome for the RI/MA South Coast, we opted for a coastal flood
advisory in case we do see a storm surge as high as 2 ft, which
would result in some minor inundation on vulnerable shoreline roads.
But overall, we expect only minor impacts.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Coastal Flood Advisory until 11 AM EDT this morning for MAZ020-
021.
RI...Coastal Flood Advisory until 11 AM EDT this morning for RIZ002-
004>007.
MARINE...Small Craft Advisory until 4 PM EDT this afternoon for ANZ230-
236.
Small Craft Advisory until 8 PM EDT this evening for
ANZ231>234-251.
Small Craft Advisory until 5 AM EDT Tuesday for ANZ235-237.
Gale Warning until 5 PM EDT this afternoon for ANZ250-254.
Small Craft Advisory until 8 AM EDT Tuesday for ANZ255-256.
&&
$$
SYNOPSIS...Loconto/KP
NEAR TERM...KP
SHORT TERM...KP
LONG TERM...Loconto/KP
AVIATION...Hrencecin/KP
MARINE...Dooley/KP
TIDES/COASTAL FLOODING...Loconto/KP
Source:
BOX issues Area Forecast Discussion (AFD) at Oct 20, 7:32 AM EDT----------------
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