Old Res Weather

Lexington, Massachusetts, USA

35°F

2/16/2025 7:17pm

Lexington Conditions: Clear
Temperature: 35.1°F / 1.7°C
Dew Point: 32.4°F
Relative Humidity: 90%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.00 in Falling Slowly
Visibility: 10 miles
Rain Today: 0.01 in
UV Index: $VPuv None

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 122354
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
754 PM EDT Wed Aug 12 2026

.WHAT HAS CHANGED...
Growing risk for late evening and overnight showers and storms 
mainly south of the Mass Pike, but severe weather isn't 
anticipated from these storms.

&&

.KEY MESSAGES...

- Showers and thunderstorms move east-southeast from NY after 
  midnight and overnight, mainly for areas south of the Mass 
  Pike. Turning more humid too.

- Early cloud cover Thursday dissipates, but isolated to widely
  scattered showers/weaker storms develop across northern MA.

- Becoming cooler and less humid Friday through Saturday night.
  A period of showers and possible thunderstorms Sunday
  afternoon into Monday Night. Dry weather should return Tuesday
  and Wednesday.

&&

.DISCUSSION...
KEY MESSAGE 1...Showers and thunderstorms move east-southeast from 
NY after midnight and overnight, mainly for areas south of the 
Mass Pike. Turning more humid too.

Seasonably mild with tolerable humidity levels currently as of 
Wednesday afternoon, but we're looking at some changes to our 
airmass over the next 12-24 hours. Couple weak impulses in broad
WNW flow aloft are contributing to scattered showers with a few
thunderstorms. One is working through far northeast Ontario, 
responsible for the area of showers and storms over VT/northern 
NY. These should pass to our north but a couple could clip part 
of Essex County and the North Shore through sundown. 

The more significant feature to Southern New England comes in
the form of a weak impulse on water vapor imagery near the 
northern portion of Lake Michigan, which is currently helping to
produce scattered showers and storms when coupled with 
isentropic ascent associated with a surface warm front/higher 
dewpoints in the mid 60s over Greater Toronto and Buffalo NY 
areas. NBM and CAMs were previously slow to resolve these, but 
the past few cycles have shown more of a risk for showers and 
storms more concentrated along and south of the Mass Pike and 
particularly for the Hartford-Providence- southeast MA area 
around/after midnight and into overnight. Mid- level lapse rates
around 6 to 6.5 C/km but with dewpoints rising into the mid 
60s, most-unstable CAPE values rise to about 1000-1200 J/kg in 
the CT-RI area. Expect a few thunderstorms to be around but 
should be elevated, with a couple stronger storms capable of 
frequent lightning, pea to dime size hail and wind gusts around 
40 mph as they move off toward the southeast at a fairly good 
clip given fast WNW winds aloft. Not thinking storms rise to the
level of severe weather. Otherwise, will turn a bit more humid 
than it's been but not oppressive, with lows in the mid to upper
60s. 

KEY MESSAGE 2...Early cloud cover Thursday dissipates, but
isolated to widely scattered showers/weaker storms develop 
across northern MA.

Showers/embedded storms from overnight should be peeling
offshore early Thursday morning, with considerable cloudiness 
around during the morning hours. Gradual heating and mixing 
should allow for cloud cover to scatter out. While most of the 
day should be more-or-less dry, there is a risk for mid-
afternoon showers or weak thunderstorms mainly north of the Mass
Pike as a stronger shortwave trough aloft moves from northern 
Quebec into ME/NH and swings a cold front southward. I think the
coverage and strength of showers or weak storms could be 
limited by drier air aloft, to go along with delayed 
heating/destabilization, so have capped PoPs to no more than 
30%. So while Thursday ends up dry, there should be some showers
or weak storms to dodge Thursday afternoon through sundown, but
nothing that looks hazardous. Will begin to turn less humid 
late upon cold frontal passage.

KEY MESSAGE 3...Becoming cooler and less humid Friday through  
Saturday night. A period of showers and possible thunderstorms 
Sunday afternoon into Monday Night. Dry weather should return 
Tuesday and Wednesday.

Gaining some clarity that a cold front should be over the
coastal waters friday morning and moving farther offshore 
during the day. High pressure then settles across southern New 
England for Saturday, before it too moves offshore Sunday. The 
main impact will be drier and cooler conditions during this 
time.

Anticipating a brief change back to more humid conditions late 
Sunday into Monday night. This should be when a low pressure 
passes by to our north, but drags its associated fronts through 
southern New England. The combination of the increased humidity 
and the lift from some front means at least a period of showers.
Not overly concerned about thunderstorms just yet, but will 
need to keep this in mind with later forecasts. This should not 
be a washout this entire time, but the greatest risk for showers
looks to be Sunday night. 

A large high pressure over the Midwest should start nudging into
our region Tuesday and be more of a factor in our weather 
during the middle of next week.

&&

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

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

Tonight: High confidence in trends, but moderate confidence in 
timing.

VFR initially, but SHRA/embedded weak TS coming in from the NW 
after 03z will deteriorate conditions into the VFR/MVFR range. 
BKN/OVC VFR/MVFR ceilings with SHRA more likely for BDL, but 
have left as PROB30s after 06z for BOS, PVD and ORH and the Cape
airports. Winds become SW 5-10 kt.

Thursday: Moderate confidence. 

Lingering SHRA/possible TS mainly PVD and Cape airports should 
move offshore by 14z. Leftover SCT/BKN VFR/MVFR decks should 
begin to scatter out by 15-17z, which will increase the risk for
SHRA/TS mainly from the Mass Pike north as sfc cold front moves
through. Coverage looks too spotty for a TAF mention but will 
need to be considered in later TAF issuances. Winds SW to W 
under 10 kt, then shift to WNW/NW 5-10k kt after 20z. 

Thursday Night: High confidence.

SHRA dissipates early to VFR. NW winds 5-10 kt. 

KBOS Terminal...High confidence.

KBDL Terminal...High confidence.

Outlook /Friday through Monday/...

Friday through Saturday Night: VFR. 

Sunday: VFR. Breezy. Chance SHRA.

Sunday Night: VFR. Breezy. Chance SHRA, slight chance TSRA.

Monday: VFR. Breezy. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Thursday Night: High confidence. 

Sub-SCA winds and seas through the period. N winds under 10 kt
shift to SW early tonight around 10-15 kt, then remain so until
frontal passage late Thurs/early Thurs night with windshift to 
NW around 10-15 kt. Seas 3 ft or less all waters. Possible
thunderstorms over mainly southern waters overnight tonight,
then more isolated SHRA Thurs afternoon over northeast waters.

Outlook /Friday through Monday/...

Friday through Saturday Night: Winds less than 25 kt. 

Sunday: Winds less than 25 kt. Slight chance of rain showers. 

Sunday Night: Winds less than 25 kt. Areas of rough seas.
Chance of rain showers, slight chance of thunderstorms. 

Monday: Winds less than 25 kt. Areas of rough seas. Chance of
rain showers. 

&&

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

&&

$$

DISCUSSION...Belk/Loconto
AVIATION...Belk/Loconto
MARINE...Belk/Loconto