Leominster, Massachusetts 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

285
FXUS61 KBOX 141725
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
125 PM EDT Wed May 14 2025

.SYNOPSIS...
Weakening low pressure will bring scattered showers or thunderstorms
at times through the end of the week as it reaches New England, but
a majority of the time will be dry. A cold front will bring a better
chance of showers and thunderstorms Saturday, then cooler and drier
air will follow early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Updated 130 PM

Key Message:

* Scattered showers or a stray thunderstorm.

Band of showers that has been focused to our west has had a
tough time making it into SNE thanks to strong and persistent
ridging aloft. Drier air in place has certainly been winning the
battle and even locations near CT River that had a few showers
earlier have dried out. Of note is a band of thunderstorms north
of PHL that seems to have formed on nose of 850 jet collocated
with northern edge of MUCAPE axis.

All of this activity will finally shift into SNE tonight as
ridge shifts farther east but will fall apart (into more
scattered showers) as it outruns better lift and instability as
short wave dampens out. Still can`t rule out a stray storm
overnight, especially near South Coast where what`s left of
MUCAPE passes offshore.

Persistent E/SE flow combined with increasing lower level
moisture will bring plenty of low clouds and patchy fog
overnight.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
Updated 130 PM Wed:

Key Message:

 * More humid with a passing shower/storm Thu and Fri.

Slow moving surface low lingers near us Thu into Fri. Not much
in way of upper dynamics nearby to generate much more than
widely scattered diurnal showers or thunderstorms both days,
more of the "garden variety" type given lack of instability,
deep layer shear, or mid level lapse rates. Interesting to note
that a majority of the high-res guidance, including RRFS, hints
that locations in western/central MA are more favored, where we
have most instability and some enhanced lift from terrain.

Also of note is potential for MCS development Thu night into
Fri from Great Lakes into Northeast, again as shown by RRFS, but
as is often the case, any such system should pass to our SW
where instability is greater. Certainly something to keep an eye
on though.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Updated 130 PM Wed

Key Messages:

 * Potential for severe thunderstorms Saturday.
 * Turning drier and cooler early next week.

Seeing fairly good agreement among models that warm front will lift
through SNE Sat morning placing us in warm sector for much of day
before cold front approaches late. It`s a bit too early to focus in
on details but overall pattern suggests cold front reaches us too
late which may limit severe weather potential. This has look of a
typical low CAPE higher shear environment with weak mid level lapse
rates, and whenever we see a closed low nearby that tends to
heighten our awareness since they have been shown through CSTAR
research to be associated with severe weather, although in this case
upper flow is more W/SW than S which will limit deep moisture from
being advected in. That said, ML Severe Weather Probs from both NSSL
and Colorado State show rather high probabilities in SNE Saturday so
the threat still exists. Localized wind damage would be main threat
from thunderstorms but given large number of outdoor events,
everyone should be aware of potential for lightning Saturday and
have a safety plan ready.

Beyond that, our blocky pattern persists as upper low meanders
around Maritimes and keeps region in cyclonic flow as ridging builds
over Great Lakes. This means a drier and somewhat cooler pattern for
early next week, but colder air aloft should bring diurnal clouds
and perhaps even a brief shower Mon/Tue.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

18z TAF Update: Moderate confidence.

Lower cigs have been slow to make progress into SNE and we will
trend things slower with MVFR cigs over western New England not
making it into RI/E MA until this evening. Band of showers
mainly to the west will primarily affect BAF/BDL through the
evening before becoming more scattered in nature. As far as TS,
it`s possible we see a stray storm overnight especially near
South Coast.

Higher confidence that IFR cigs become more widespread
overnight and last into Thu morning before slowly lifting to
MVFR in the afternoon. Potential for widely scattered showers or
a thunderstorm especially in western/central MA and CT. Similar
conditions Thu night/Fri with lowering conditions to MVFR/IFR at
night and improvement to VFR Fri with scattered afternoon TS.

KBOS TAF...Moderate confidence. Onset of MVFR may still be too
fast but higher confidence in IFR overnight and Thu.

KBDL TAF...High confidence.

Outlook /Friday Night through Monday/...

Friday Night: Mainly VFR, with local IFR possible. Chance SHRA,
isolated TSRA.

Saturday: MVFR/IFR conditions possible. Chance SHRA, isolated
TSRA.

Saturday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.

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

Sunday Night: VFR. Breezy. Slight chance SHRA.

Monday: Breezy. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Updated 130 PM Wed:

E/SE winds remain below SCA tonight and Thu but expect building
seas to 3-6 ft on open south coastal waters where we have SCAs
posted. Few showers or a thunderstorm possible later tonight
with areas of fog, which should slowly lift Thu and develop
once again Thu night into Fri.

Outlook /Friday Night through Monday/...

Friday Night: Winds less than 25 kt. Slight chance of rain
showers, isolated thunderstorms.

Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers, isolated thunderstorms.

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

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 10 PM this evening to 4 PM EDT
     Thursday for ANZ235-237.
     Small Craft Advisory from 10 PM this evening to 1 AM EDT
     Friday for ANZ254-255.
     Small Craft Advisory from 6 PM this evening to 1 AM EDT Friday
     for ANZ256.

&&

$$

JWD