168
FXUS61 KBOX 180615
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
215 AM EDT Fri Sep 18 2026

.WHAT HAS CHANGED...
No significant forecast changes.

&&

.KEY MESSAGES...

- Shower chances into Friday morning, followed by drier
  conditions Friday.

- Drier conditions Friday and Saturday.

- Next chance for rain Sunday into Monday. There remains
  uncertainty in the details such as coverage, timing, amounts.
  Showers may linger through early next week.

&&

.DISCUSSION...
KEY MESSAGE 1...Shower chances into Friday morning, followed by
drier conditions Friday.

Majority of the showers were moving across northern New England
this evening. These showers were ahead of a cold front just
about to enter southern New England as of this writing. It will
take just about all night to move this front past our region.
Currently thinking it should be over SE MA and perhaps southern
RI toward daybreak Friday. It could as late as late morning for
it to completely move past the coastal waters as well.

PWATs are quite anomalous for mid-September, nearing 2+ inches,
which is near the maximum of climatology based on sounding
climatology at Chatham. The threat of thunderstorms is low,
though not zero. There is also a low threat of localized heavy
downpours due to the anomalous moisture in the atmosphere, but
these showers are moving at a good pace. Nevertheless, rainfall
amounts will be highly variable given the showery nature. There
is potential for as much as a half inch of rain in the vicinity
of Rt. 2 in northern Massachusetts and into southern Vermont and
southern New Hampshire, with much less the farther south you
go.

KEY MESSAGE 2...Drier conditions Friday and Saturday.

A few early morning showers are possible across Cape Cod and the
Islands; otherwise, a transient high pressure system moving out
of the southern Canadian Prairies brings a dry stretch of
weather Friday and Saturday. Seasonably mild temperatures are
expected Friday, with highs in the middle 70s and elevated dew
points initially in the lower 60s, though those fall into the
upper 40s by Friday afternoon. Breezy NW winds in the afternoon
with gusts 20-25 mph, mainly across the interior. Then a shift
to more fall-like conditions on Saturday. A chilly start for
most, with lows in the lower to middle 40s, while urban areas
remain in the lower 50s. Not out of the question that upper 30s
occur along the east slopes of the Berkshires and across
northern Worcester County. Otherwise, a crisp afternoon with
sunshine and highs in the middle to upper 60s. Light east winds
will lead to slightly lower temperatures for eastern coastal
communities, with locations like Boston perhaps not climbing out
of the lower 60s. Dew points in the 40s will add to the crisp
feel.

KEY MESSAGE 3...Next chance for rain Sunday into Monday. There
remains uncertainty in the details such as coverage, timing,
amounts. Showers may linger through early next week.

Still have timing concerns for rainfall Sunday into Monday.
While a high pressure should be moving off the coast Saturday
night, it may still have too much influence to prevent rainfall
from overspreading our region during the morning. Still favoring
rainfall arriving from west to east Sunday afternoon into Sunday
night. Another high pressure over eastern Canada should become
more of an influence over the course of Monday. Thus, not
certain how many showers will remain Monday morning. Thinking
the greatest risk for lingering showers will be towards the
south coast.

The potential rain amounts will depend on the exact track of
this low pressure, which is still variable across guidance this
far out in time. This variance translates quite clearly to the
rain totals across both deterministic and ensemble guidance.
Moisture should not be that much of a limitation. Overall,
still looking like another soaking rainfall for most. Favoring
the highest rainfall totals towards the south coast of New
England at this time.

The forecast trend is for drier weather Tuesday and Wednesday.
It appears that another low pressure could approach from the
Mid Atlantic states sometime towards Thursday.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

06Z TAF Update:

Through 12Z...Moderate confidence.

MVFR with patchy areas of IFR and spotty VFR ceilings. Showers
push across Cape and Islands, exiting by 13Z. SW winds 6-12 kts
with a few occasional gusts to 18 kts in spots. Winds shift to
NW 06-12z with gradually improving ceilings. Moderate confidence
is with respect to the ceilings. It is possible ceilings scatter
more quickly behind the frontal passage. Current TAF keeps
lingering MVFR through 13-14Z before scattering out.

Friday and Friday Night...High confidence.

Areas of MVFR linger across Cape Cod and the Islands through
15z, otherwise VFR. NNW winds 8-12 kt with an occasional gust
up to 20 kts. There may be an additional period of gusts around
20 kts in the evening (after 00Z).

KBOS Terminal...Moderate confidence in TAF.

Cold front moves through between 07-10Z shifting winds to the
NW. Ceilings this morning bounce between low end VFR and MVFR
with improvements to solid VFR once the front pushes through.
Lower confidence on exact timing, but should be likely be VFR by
13Z. Winds increase after 15Z to 8-12 kts with a few gusts
around 18 kts today. Very low probability for a sea breeze to
sneak in before 15Z before the winds increase. The current pattern
should make this unlikely.

KBDL Terminal...Moderate confidence in TAF.

Outlook /Saturday through Tuesday/...

Saturday through Saturday Night: VFR.

Sunday: MVFR/IFR conditions possible. SHRA likely.

Sunday Night: Mainly VFR, with local MVFR possible. Breezy.
SHRA likely.

Monday through Monday Night: VFR. Breezy. Slight chance SHRA.

Tuesday: VFR. Windy with local gusts up to 30 kt. Slight chance
SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Saturday...High confidence.

A round of showers pushes across the waters tonight into early
tomorrow morning. Seas remain 2-3 ft, though portions of the
southern waters may approach 4 ft heading into tomorrow morning.
Winds shift to the NW tomorrow morning, with some gusts up to 20 kt
possible. High pressure builds in from the WNW Friday afternoon and
remains with us through Saturday. Briefly Friday night into early
Saturday, gusts may approach Small Craft Advisory criteria.
Confidence in gusts exceeding 25 kt is low; however, gusts of 20 to
25 kt seem likely. Future forecast updates may include an advisory
if confidence in higher gusts increases. Otherwise, nice conditions
on Saturday with seas 2-3 ft and ENE winds less than 15 kt.

Outlook /Saturday through Tuesday/...

Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft.

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

Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers.

Sunday Night: Winds less than 25 kt. Areas of rough seas. Rain
showers likely.

Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. Chance of rain showers.

Monday Night: Low risk for Small Craft Advisory winds with
local gusts up to 30 kt. Seas up to 5 ft. Chance of rain
showers.

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft. Chance of rain showers.

&&

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

&&

$$

DISCUSSION...Belk/Dooley
AVIATION...Mensch
MARINE...Belk/Dooley