383
FXUS61 KBOX 291756
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
156 PM EDT Tue Sep 29 2026

.WHAT HAS CHANGED...
The River Flood Warning for the Taunton River at Bridgewater was
extended into Wednesday based on latest NERFC river forecasts.
Otherwise no significant changes.

&&

.KEY MESSAGES...

- Drier and warmer weather through Friday.

- Passing frontal boundary brings light rain showers Friday
  night into early Saturday, then drying out Saturday with
  onshore breezes for the Cape and Islands. Cloud cover and
  possible showers return Sunday, but it is uncertain how far
  north rain would extend.

- Dry weather, but blustery and a much cooler, Fall-like airmass
  returns for early to mid next week.

&&

.DISCUSSION...
KEY MESSAGE 1...Drier and warmer weather through Friday.

No big changes to model guidance for the next few days. The overall
synoptic scenario that will play out is that a rather weak surface
high pressure will move across the region on Wednesday and then
strengthen and establish itself off the East Coast for Thursday and
Friday.  As this happens, the northwest winds we currently have on
the backside of the nor`easter will transition to light westerly
Wednesday and then to southwesterly Thursday and Friday. This will
all help to transport warmer temperatures at low and mid levels.
Aloft, ridging will also develop along the east coast. The net
result will be dry weather through Friday. However we won`t be
seeing fully sunny days to go along with the high pressure. There
will still be some residual low level moisture on Wednesday thanks
to that nor`easter that will result in areas of strato-cu. That will
especially be the case across eastern areas. Still there will be
more sunshine than we got today. On Thursday, it looks like mid and
high level clouds will flow across the region from the storminess
across the central part of the country.  Friday will probably end up
as the sunniest of the days.  As mentioned, temperatures will be
warming. 925mb temperatures today are in the 11-13C range and will
increase to 12-15C Wednesday, 16-18C Thursday and then 20-22C on
Friday. If we had full sunshine and excellent boundary layer mixing,
adding about 10C to those values would give a good estimate for
daytime highs. That won`t quite be the case, but still enough to
push temperatures into the low 70s Wednesday, mid-upper 70s Thursday
and low 80s Friday. Stuck with the NBM blend for those temperatures
as they seemed reasonable enough. Overnight lows will also remain
above normal, and Thursday night most of the area will stay in the
60s. Lows around 50F are normal for the end of September/start of
October.

KEY MESSAGE 2...Passing frontal boundary brings light rain
showers Friday night into early Saturday, then drying out
Saturday with onshore breezes for the Cape and Islands. Cloud
cover and possible showers return Sunday, but it is uncertain
how far north rain would extend.

A progressive cold frontal boundary moves in from the Gt
Lakes/northern Appalachians Fri night into early on Sat AM, which
will bring an end to the spell of late-week warmer temperatures.
Although the front looks to have some moisture with it (PWATs around
1.4" per 15z SREF mean), the better forcing passes to the north and
weakens/becomes sheared out with time. Expect there to be clouds and
light showers but total rains look to be around a quarter inch or
less with this frontal boundary.

We get into strong surface ridging building in from the northwest in
the wake of the frontal boundary on Saturday; with the frontal
boundary stalling south of the Long Island waters. Expect mostly
sunny conditions, with a mix of sun and clouds and northeast breezes
toward southeast MA/eastern RI, Cape Cod and the Islands which will
keep those areas cooler than further inland. Highs mainly in the mid
60s to near 70 for most, but cooler low 60s for highs for the Cape.
Lows in the mid 40s for interior Southern New England with good
radiational cooling, but in the low to mid 50s near the coast where
NE winds still hang on helping to keep the PBL more mixed and less
prone to decouple.

Sunday into Sunday night is the more uncertain element of the
weekend forecast. The stalled frontal boundary begins to draw
northward an influx of rich moisture from the southeast US states
with weak/nebulous 500 mb vort energy riding along it. This shield
of rain will be moving into the drier antecedent airmass in place
over the Northeast states; 12z guidance conveys uncertainty how far
north this moisture/rain makes it, which is seemingly tied to the
extent to which the existing sfc ridge weakens, if it does so at
all. The best chance for rain showers on Sunday looks to be for the
southern third of Southern New England with less of a chance the
further north one goes with ridging still holding on, but will
maintain NBM-based slight to chance PoP CWA-wide for now until there
is more congruence in the models.

KEY MESSAGE 3...Dry weather, but blustery and a much cooler,
Fall-like airmass returns for early to mid next week.

The frontal boundary to our south moves offshore early on Monday,
and behind it comes a seasonably strong mid/upper level trough and
associated 1030 mb Canadian anticyclone into New England. This
feature brings dry weather but increasingly breezy conditions and
also brings with it the coldest low-level airmass seen to this point
in early-autumn. By 12z Tuesday, our 925 mb temperatures drop to a
chilly -2C! Climatological high temperature normals for this time of
year are in the mid 60s, and we could run some 5-10 degrees cooler
than those normals into early next week, with cooler breezes
too.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

18z TAF Update...

Today and Tonight...High confidence in trends.

MVFR, low level moisture will remain in place, resulting in
widespread ceilings of 2k-2.5kft for most areas much of the day,
although there may be patchy 3k CIGS at times. WNW to NW winds 5
to 10 kt, becoming light to calm overnight. Wednesday...High
confidence.

VFR. Light WNW winds, though ESE winds for eastern coastal MA
and SW wind for southern RI and the Islands.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Wednesday Night through Sunday/...

Thursday through Thursday Night: VFR. Breezy.

Friday through Friday Night: VFR. Breezy. Chance SHRA.

Saturday: VFR. Breezy.

Saturday Night: VFR.

Sunday: Mainly VFR, with local MVFR possible. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Overall high confidence.

As the nor`easter continues to pull away, winds and seas continue to
subside. The remaining rougher sea conditions across our eastern
marine zones have finally fallen below SCA thresholds. High pressure
will become established off the east coast, setting up southwest
flow across the region beginning later tomorrow and continuing into
Friday.  We may start to see seas building toward 5 feet by late
Thursday/early Friday across the southern waters due to the
sustained southwest winds.

Outlook /Wednesday Night through Sunday/...

Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.

Thursday Night through Friday: Winds less than 25 kt. Seas up
to 5 ft.

Friday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers.

Saturday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain showers.

Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers.

Sunday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain
showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$

DISCUSSION...Loconto/Nash
AVIATION...Loconto/Dooley/Nash
MARINE...Loconto/Nash