BOX issues Area Forecast Discussion (AFD) at Oct 13, 4:22 AM EDT569
FXUS61 KBOX 130822
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
422 AM EDT Tue Oct 13 2026
.WHAT HAS CHANGED...
No significant changes to the forecast. See Marine section for
notes on coastal water levels at Nantucket.
&&
.KEY MESSAGES...
- Low clouds continue to move in this morning, lasting into
Tuesday night. Rain showers possible heading into Tuesday
night, as well as early this morning.
- Isolated shower possible Wednesday, but drier overall. Dry
conditions return Thursday with seasonably cool temperatures.
- Low pressure system expected to bring rain Friday into early
Saturday. Gusty NW winds and below normal temperatures
expected to be left in its wake.
&&
.DISCUSSION...
KEY MESSAGE 1...Low clouds continue to move in this morning, lasting
into Tuesday night. Rain showers possible heading into Tuesday
night, as well as early this morning.
Low clouds have continued to descend across southern New England
from the north as a backdoor front pushes in from the north. Some
patchy drizzle remains possible this morning, particularly closer to
the MA/NH/VT border. Latest HREF guidance indicates the possibility
for two rounds of showers across the region today: one round later
this morning, then another this evening heading into early tonight.
Latest guidance has shown that these may extend a bit more south
into SE MA, including the Cape and Islands this evening. Low
pressure associated with a shortwave moving across northern New
England is the primary driver for the later showers, which could
lead to them becoming more robust towards northern MA.
Notably, lows Tuesday night will be a bit warmer following this
disturbance as the flow shifts more SW and 925 mb temperatures climb
to nearly 18C overnight. Lows will likely only be in the 50s to low
60s ahead of quite a warm day for Wednesday.
KEY MESSAGE 2...Isolated shower possible Wednesday, but drier
overall. Dry conditions return Thursday with seasonably cool
temperatures.
The low centered over northern New England continues tracking off to
the northeast and surface high pressure with upper level ridging
begins to build in over SNE behind it. With the continued westerly
winds, downslope flow with the aforementioned elevated low level
temperatures (~18C at 925 mb) and good mixing with the boundary
layer will all combine to support a much warmer fall day. Highs will
likely climb into the 70s, with some areas even approaching 80.
Based on the latest ensemble probabilities, the highest temperatures
are most likely towards the CT Valley and in much of the coastal
plain of SE MA, where highs are expected to reach well into the
upper 70s. With the westerly downsloping flow, gusts around 25 mph
are not out of the question, especially for the higher elevations
Wednesday afternoon.
Isolated showers remain a possibility Wednesday given the trailing
cold front associated with the disturbance to our north and PWATs
remaining quite elevated. Latest CAMs have a signal for some of
these showers towards the afternoon towards eastern MA and RI.
Guidance generally has PWAT values between 1.0-1.25" Wednesday,
drying out considerably heading into Wednesday night and Thursday
with high pressure and a drier airmass over eastern Ontario
continuing to build east. 925 mb temperatures Wednesday night drop
drastically compared to the afternoon, falling to below 10C and
generally remaining there through Thursday. This will be supportive
of lows dipping back into the 40s and 50s with daytime highs
Thursday in the 60s. With high pressure in full force Thursday,
expect drier and more seasonably cool conditions.
KEY MESSAGE 3...Low pressure system expected to bring rain Friday
into early Saturday. Gusty NW winds and below normal temperatures
expected to be left in its wake.
A deeper, more potent shortwave is expected to deepen well into the
Great Lakes region heading into Friday morning and continue tracking
east into the northeastern US Friday into Saturday. Latest guidance
indicates a LLJ from the SW may set up over the region in
conjunction with an anomalous moisture plume of PWATs up to around
1.5" Friday, which given this environment is quite favorable for
widespread rain. However, instability is quite lacking across the
guidance, so heavier downpours aren't as favored. Ensemble totals
for this event range between 0.30" to around 0.75", with the
Canadian and the ECMWF ensembles favoring the wetter solutions for
southern New England. Given the time out from this system, more
refined timing details are a bit uncertain at this time, but the
general idea across the guidance is that rain moves in sometime
Friday morning and moves out Saturday morning.
Following this rainfall, a strong cold front is expected to push
through the region Saturday morning, kicking off strong cold air
advection underneath more cyclonic flow. Latest guidance even has
the 540dam line extending south into southern New England as 925 mb
temperatures sink below 0C Saturday. PWATs fall below 0.25" as this
dry, cold air sets in. Lows Friday night fall into the 40s and upper
30s, with the higher elevations likely falling below to at freezing.
Highs Saturday may struggle to reach the low 50s across the interior
and lows Saturday night will likely dip below freezing across the
region, with the exceptions being areas closest to the coasts and
urban areas. In the midst of this colder air, strong NW winds
prevail, with gusts to 45 mph becoming a possibility given the
steeper lapse rates and tight gradient between the exiting strong
low and high pressure situated well to our SW.
&&
.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06Z TAF Update:
Through 12z...High confidence in trends, but moderate on timing
of lowering ceilings and showers.
A backdoor cold front progresses southward from NH/ME. Lower
ceilings have started to move in, already reaching MVFR at ORH.
BED remains just above MVFR as of the latest TAF issuance,
though should also come down in the next few hours. This will
continue tracking from NE to SW into the morning hours. Ceilings
will continue to drop into the MVFR to IFR range within the next
few hours, with winds turning NE around 5-10 kts.
Light SHRA possible, but likely to be quite scattered in
coverage and closer to the MA-NH border. Vsbys 4-6SM with
potential for a period of 1/2 to 3/4SM at ORH.
Today...Moderate confidence.
MVFR-IFR ceilings, with -SHRA or -DZ. Likely a round early AM
and evening/early overnight round of showers. Used PROB30s,
VCSH due to the lower confidence in showers and coverage at
BOS/BED/ORH. Potential for patchy LIFR, though somewhat low
confidence. NE winds around 5-10 kts, turning S/SE by afternoon
and increasing to around 8-12 kts.
Tuesday Night...Moderate confidence.
MVFR-IFR for most. Areas in western MA and CT improving toward
VFR after 10z. Breezy S/SW winds up to 15 kt particularly
towards the Cape and Islands. Elsewhere, ranging between 5-12
kt. LLWS could be a concern overnight.
Wednesday...Moderate confidence.
Improvement to VFR across the region through the morning hours,
especially after 12z; lower cigs may linger a bit over the Cape
and Islands. Breezy W winds with gusts to 25 mph possible for
the higher elevations and towards the Islands.
KBOS Terminal...High confidence in trends. Moderate confidence
in timing.
KBDL Terminal...High confidence in trends. Moderate confidence
in timing.
Outlook /Wednesday Night through Saturday/...
Wednesday Night through Thursday: VFR. Breezy.
Thursday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.
Friday: Mainly VFR, with local IFR possible. Windy with local
gusts up to 30 kt. SHRA, slight chance TSRA.
Friday Night: Mainly VFR, with local IFR possible. Strong winds
with local gusts up to 40 kt. Chance SHRA.
Saturday: VFR. Strong winds with local gusts up to 40 kt.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through Wednesday...High confidence.
E to SE winds 10-25 kt, gusting to 20 to 25 kt. Gusts increase
heading into Tuesday night and Small Craft Advisories remain in
effect through Wednesday evening. Seas increase Tuesday night
into Wednesday, generally ranging between 5-7 ft for the outer
waters and up to 8 ft for the ocean waters. RA possible mainly
Tuesday night across the eastern waters. Seas and winds drop off
Wednesday night, falling below SCA criteria.
Regarding the water levels at Nantucket: latest guidance and
observations indicate that they should remain just below Minor
flood criteria for this morning's high tide. At most, some
splashover can be expected, but not much more than that.
Outlook /Wednesday Night through Saturday/...
Wednesday Night through Thursday: Low risk for Small Craft
Advisory winds with gusts up to 25 kt. Seas up to 5 ft.
Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.
Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Local rough seas. Rain showers, slight chance of
thunderstorms.
Friday Night: Moderate risk for gale force winds with gusts up
to 40 kt. Rough seas up to 14 ft. Chance of rain showers.
Saturday: gale force winds with gusts up to 40 kt. Rough seas
up to 15 ft. Chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 2 AM EDT Wednesday for ANZ250.
Small Craft Advisory until 8 PM EDT Wednesday for ANZ254.
Small Craft Advisory until 8 AM EDT this morning for ANZ255-
256.
Small Craft Advisory from 1 AM to 8 PM EDT Wednesday for
ANZ255-256.
&&
$$
DISCUSSION...Hrencecin
AVIATION...Hrencecin
MARINE...Hrencecin
Source:
BOX issues Area Forecast Discussion (AFD) at Oct 13, 4:22 AM EDT----------------
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