Leominster, Massachusetts 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

061
FXUS61 KBOX 180012
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
712 PM EST Wed Dec 17 2025

.WHAT HAS CHANGED...
Wind Advisories added for southern New England, except for the Cape
and Islands where a High Wind Watch remains. This will be in effect
early Friday morning through early Saturday morning.

&&

.KEY MESSAGES...

- Dry weather with mild temperatures Thursday.

- Widespread rain with strong to possibly damaging winds late
  Thursday night into Friday.

- The risk for minor coastal flooding for south-facing shore during
Friday morning high tide has diminished.

- System moves through late Saturday into Sunday bringing light rain
Saturday and gusty winds for Sunday.

&&

.DISCUSSION...
KEY MESSAGE 1...Dry and milder Thursday.

Expect to see winds drop off overnight tonight into Thursday
morning, with even warmer temperatures in the mid 40s to low
50s.

KEY MESSAGE 2...Locally heavy rainfall and strong to possibly
damaging winds.

A deep trough moves across the northeast late Thursday and Friday.
Ahead of this trough a strong LLJ, several standard deviations above
normal in magnitude develops. This will help transport above normal
moisture into the region (200-300% of normal). PWATS have also been
flagged by NAEFS as considerably above normal values. This will
support not only rain, but a period of heavy rainfall. In terms of
timing of the rain, showers are possible Thursday night, becoming
more steady into early Friday morning. Strong convergence and
marginal instability later Friday morning into early afternoon will
bring the additional forcing to bring a period of moderate to heavy
rain with perhaps an isolated rumble of thunder. This system should
be quick moving which will limit the potential for this being an
excessive rainfall event. Ensemble guidance shows values 0.50-1.00"
for rain totals with indications of locally higher amounts. This is
consistent with the potential for a few weak thunderstorms and the
upper percentiles of ensemble guidance. Localized spots may receive
1-2 inches in the more persistent downpours. Given the morning
timeframe, this means it may impact the morning commute on Friday.
Minor urban and poor drainage street flooding is possible, but given
the quick progression of the rain, no major flooding impacts are
expected. As the cold front pushes through in the afternoon, there
will be strong drying behind it which will taper off the rain other
than some scattered showers in the afternoon/evening as the trough
approaches. Any showers over the high terrain will become more
favored as light snow showers or flurries in the early evening.

Regarding the wind potential...a 70-80 kt LLJ develops across
southeast southern New England Friday morning with the strongest
core of the winds shifting over the Cape and Islands toward the
afternoon. The challenge (as it usually is with southerly LLJ
events) is how much wind will mix down to the surface. Model
soundings display an inversion in the thermal profiles across
southern New England Friday morning with a stronger inversion
present over the Cape/Islands. What this means is that we will need
additional warming to efficiently mix down the stronger winds aloft.
Model guidance indicates continued warm air advection Friday morning
with subtle differences in how warm it ends up getting. We will
likely need temperatures around 57-59F for the deeper mixing. Now
that we are getting in high-resolution guidance, it is appearing to
be close with temperatures warming into the mid-50s with some
solutions showing temperatures approaching 60 as the LLJ shifts
across. Using more conservative approach, given the uncertainty of
deeper mixing, 50-60 percent yields gusts 40-55 mph with the
strongest gusts SE MA, most consistently for the Cape/Islands late
AM to mid-afternoon. If temperatures end up warmer, gusts 60+ are
possible. Ensemble guidance continues to highlight moderate
probabilities for 50 kts or greater for SE MA as well as portions of
the south coast. Pressure falls and even the marginal convection may
also be features that can contribute to bringing down stronger
gusts. With reasonable justification for the potential of high
winds, the Cape/Islands remain in a High Wind Watch. As
confidence in the thermal profiles increases this will be
converted to either a Warning or Advisory. Wind Advisories have
been added for the rest of southern New England.

Another round of strong winds are possible Friday night into early
Saturday. Strong cold advection behind a cold front and 40-50 kt
westerly LLJ will promote a period of strong west winds. Ensembles
show high probabilities for gusts 40 mph or greater for the higher
terrain of the interior and Cape/Islands. Model soundings show
potential for gusts 45-55 mph. With the additional downslope
enhancement off the slopes of the Berkshires, can`t rule out a
gust or two to 60 mph Friday night. Advisories extend through
Saturday morning to cover this period, but it is possible that
the more consistent advisory (45 mph+) level gusts stay confined
to the higher terrain and Cape/Islands rather than all of
southern New England.

KEY MESSAGE 3...Diminishing risk for minor coastal flooding

Latest guidance continues to suggest the timing of the low level jet
and highest surge will occur a few hours after high tide Fri morning
which would likely preclude minor coastal flood impacts along the
south coast. The greatest risk would be for Narragansett Bay and
Buzzards Bay, but it would take a storm surge of 2.5 to 3 ft during
high tide to produce minor flooding. Latest guidance from the
Stevens Institute indicated a 2-2.5 ft surge for Providence but
occurring after high tide. The 95th percentile which represents a 5
percent exceedance probability has Providence slightly exceeding the
7 ft flood stage but this is a very low probability at this time. It
would take more favorable timing of the strongest winds at high tide
and a worst case wind forecast to realize this potential, which
would yield just minor flooding impacts along Narragansett and
Buzzards Bay.


KEY MESSAGE 4...System moves through late Saturday into Sunday
bringing light rain and gusty winds.

A mid-level shortwave trough moves through late Saturday into
Sunday. Moisture will be fairly marginal which will limit
precipitation to scattered light showers. A SW 40-60 kt LLJ nudges
northward Sunday night bringing at gusts 30-40 mph to at least the
coastal waters. This will be followed by a front which will favor
efficient mixing from the higher winds aloft while in the CAA regime
on Sunday. Still further out, but gusts 30-40 mph are possible in
the afternoon.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...

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

00Z TAF Update: High confidence.

Tonight and Tomorrow ...High Confidence

VFR. W this evening become light overnight, then shift
southerly around 10 kt Thu afternoon.

Tomorrow Night...High Confidence in trends

MVFR/IFR ceilings overspread the region from west to east
tomorrow night with RA. Winds increase out of the south
with sustained speeds of 15 to 20 knots and gusts approaching
25 to 35 knots by Friday morning.


KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Friday Night through Monday/...

Friday: Mainly MVFR, with local IFR possible. Strong winds with
gusts up to 45 kt. RA.

Friday Night: VFR. Strong winds with gusts up to 45 kt.

Saturday: VFR. Windy with local gusts up to 30 kt.

Saturday Night through Sunday: VFR. Windy with local gusts up
to 30 kt. Slight chance RA.

Sunday Night: VFR. Windy with local gusts up to 30 kt.

Monday: Breezy.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Thursday...High confidence.

Winds decrease and seas subside briefly during the day Thursday.
Winds increase late Thursday night into Friday morning with Gale
force winds likely by 12Z Friday continuing through Saturday
morning. Seas increase to 6-10 ft Friday over the outer waters
with 10-12 ft possible for the southern outer waters late AM to
early afternoon Friday.

Outlook /Friday Night through Monday/...

Friday: gale force winds with gusts up to 45 kt. Rough seas up
to 16 ft. Rain.

Friday Night: gale force winds with areas of gusts up to 45 kt.
Rough seas up to 16 ft. Slight chance of rain.

Saturday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Rough seas up to 11 ft.

Saturday Night: Low risk for gale force winds with gusts up to
35 kt. Seas up to 5 ft.

Sunday: Strong winds with gusts up to 35 kt. Areas of rough
seas. Slight chance of rain.

Sunday Night: Strong winds with gusts up to 40 kt. Seas up to
5 ft.

Monday: Strong winds with gusts up to 35 kt. Areas of rough
seas.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory from 4 AM Friday to 1 AM EST Saturday for
     CTZ002>004.
MA...Wind Advisory from 4 AM Friday to 1 AM EST Saturday for
     MAZ002>021-026.
     High Wind Watch from Friday morning through Friday afternoon
     for MAZ022>024.
RI...Wind Advisory from 4 AM Friday to 1 AM EST Saturday for
     RIZ001>008.
MARINE...Gale Warning until 7 PM EST this evening for ANZ230>237-251.
     Gale Watch from Friday morning through Saturday morning for
     ANZ230.
     Gale Watch from late Thursday night through Saturday morning
     for ANZ231>234-251.
     Gale Watch from late Thursday night through Saturday morning
     for ANZ235-237.
     Gale Watch from late Thursday night through late Friday night
     for ANZ236.
     Gale Warning until 1 AM EST Thursday for ANZ250-254>256.
     Gale Watch from late Thursday night through Saturday morning
     for ANZ250-254>256.

&&

$$

DISCUSSION...Mensch/RM
AVIATION...McMinn/Mensch
MARINE...Mensch