Lexington Weather

Lexington, Massachusetts, USA

60°F

9/20/2026 8:49pm

Lexington Conditions: Overcast
Temperature: 59.9°F / 15.5°C
Dew Point: 56.7°F
Relative Humidity: 89%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.95 in Steady
Visibility: 9 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 202339
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
739 PM EDT Sun Sep 20 2026

.WHAT HAS CHANGED...
Gale Watch has been issued for portions of the southern ocean 
waters Tuesday afternoon into Thursday.

&&

.KEY MESSAGES...

- Light rain continues this afternoon into early Monday morning.
  Breezy, cloudy, and cooler Monday afternoon.

- Dry and cool through mid week. Watching the potential for a 
  coastal low to form mid to late week, bringing chances for 
  strong winds and rainfall heading into the weekend.

&&

.DISCUSSION...
KEY MESSAGE 1...Light rain continues this afternoon into early 
Monday morning. Breezy, cloudy, and cooler Monday afternoon.

A raw, cool, and rainy afternoon continues across southern New 
England, with rain persisting through much of the evening. 
Rainfall will be predominantly stratiform with generally light 
to occasionally moderate rainfall rates. A rumble of thunder 
cannot be ruled out near the south coast, though the risk is 
quite low. Overall, additional rainfall amounts of 0.25-0.75 
inch are expected, with some localized variability. Flooding is 
not a concern with this event. Rain gradually shifts offshore 
overnight, coming to an end by or before daybreak Monday. It 
remains raw and wet overnight, with lows in the upper 40s to 
lower 50s and a breezy northerly wind.

As for Monday, showers linger just offshore along a frontal 
boundary while 1030 mb high pressure builds in from the 
northwest. This results in a tightening pressure gradient and 
breezy north-northeast winds throughout the day, especially near
the coast where gusts top out around 20-25 mph. Clouds hang 
tough for much of the day, though there may be a few glimmers of
sunshine. It will remain cool, with highs ranging through the 
60s. Clouds remain Monday night as well, with lows falling into 
the 40s across much of the region, while the urban centers 
remain in the lower 50s.

KEY MESSAGE 2...Dry and cool through mid week. Watching the 
potential for a coastal low to form mid to late week, bringing 
chances for strong winds and rainfall heading into the weekend.

Ensemble guidance remains in good agreement that an anomolously
strong high pressure system will develop over Quebec Tuesday 
and linger into Wed/Thurs. This system likely keeps temperatures
across New England cooler than normal, in the low to mid 60s, 
with a cooler airmass and several days of prolonged 
northeasterly flow. Despite the large areal coverage the 
Canadian high spans, guidance indicates the formation of a weak 
Tuesday across the Mid-Atlantic region that could push just far 
enough north into NJ to brush southern New England with spotty 
showers. Still some uncertainty in how far north that low could 
move, but general consensus in some low-end PoPs across the 
southern coast Tuesday... higher chances across southern CT, 
closer to NYC.

Both deterministic and ensemble guidance continue to indicate 
potential for a coastal low to form Wednesday into the later 
half of the week. While there is still a large amount of 
uncertainty in the forecast this time, the overarching trend has
been the low slowly meanders north into the waters south of 
Nantucket; however, each model has this low taking a slightly 
different track: the GFS pushing further NE and closer to 
Nantucket, and the ECMWF further NW and closer to Long Island. 
Regardless, this system is likely to bring strong winds, rain, 
and the potential for erosion/coastal flooding.

Highest confidence at this time pertains to winds, especially 
over the waters. As the low deepens and approaches to the south,
the Canadian high over Quebec is also likely to strengthen and 
expand, leading to a tighter pressure gradient over New England.
Given there's still uncertainty in how strong the low and high 
get as well as the track of the low, there is still some 
question as to how strong the gradient will get. However, 
confidence is increasing in the potential for Gale Force winds 
across the southern waters, and a Gale Watch has been issued for
Tuesday evening through at least Thursday morning. The latest 
ensemble guidance is also showing roughly 50 percent 
probabilities of Storm Force wind gusts across the ocean waters 
south of Long Island and Block Island as well as 20 to 30 
percent probabilities of Storm Force gusts over Nantucket Sound 
and Cape Cod Bay as the low deepens Friday into Saturday. Winds 
over land along the south coast, Cape, and Islands throughout 
the week are more likely to be a touch slower than the marine 
winds, but still gusty... more on the order of 25-35 mph.

&&

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

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

00Z TAF Update:

Through Tonight...High confidence in trends, moderate 
confidence in timing and ceilings.

MVFR to IFR with areas of -RA. The threat for LLWS has 
lessened, though it cannot be ruled out as a weaker low-level 
jet shifts across southern New England through 06z. Otherwise, 
winds generally SE to ESE at 5-10 kt. Chances for embedded 
thunderstorms are very low to near zero. IFR ceilings become 
more widespread overnight, with localized LIFR possible. 
Visibilities generally 2- 5SM with -RA continuing overnight. -RA
ends from west to east mainly between 06z-12z as winds shift to
the N at 8-12 kt.

Monday...High confidence in trends, moderate confidence in 
timing and ceilings.

IFR/MVFR improving to VFR through the day, though exact timing 
remains somewhat uncertain. NNE to NE winds increase to 10-20 
kt, with gusts up to 25 kt possible across the Cape and Islands,
where sustained winds will also be strongest. Winds diminish 
somewhat heading into Monday night.

Monday Night...Moderate confidence.

VFR, though lower-end VFR ceilings are possible near the 
southern coast and Islands, potentially impacting terminals such
as KACK. NNE winds 8-12 kt, increasing to 10-15 kt across the 
Cape and Islands.

KBOS Terminal...Moderate confidence in TAF.

IFR overnight, with ceilings improving between 10z-14z. NNE 
gusts up to 25 kt possible Monday afternoon.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday through Friday/...

Tuesday: VFR. Breezy. Slight chance SHRA.

Tuesday Night: VFR. Windy with gusts up to 30 kt. 

Wednesday: Mainly VFR, with local MVFR possible. Windy with
gusts up to 30 kt. 

Wednesday Night through Thursday: VFR. Strong winds with local
gusts up to 40 kt. 

Thursday Night: VFR. Strong winds with local gusts up to 40 kt.
Slight chance SHRA.

Friday: Mainly VFR, with local MVFR possible. Strong winds with
areas of gusts up to 45 kt. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Monday Night...High Confidence.

A low pressure system riding along a frontal boundary brings 
widespread rain to the waters this afternoon and evening. There 
is a low chance for a few rumbles of thunder, primarily across 
the southern waters. Rain ends early Monday morning, though a 
few showers could linger across the southern outer waters as the
front sags south. Winds shift from E/SE to N/NE tonight as the 
front pushes south. Gusts increase with cold air advection 
Monday morning, which has prompted Small Craft headlines for all
southern waters and Cape Cod Bay through Monday afternoon. Seas
build to 3-5 ft, with the highest seas across the outer waters.
Winds subside Monday evening, albeit briefly, ahead of another 
period of stronger winds Tuesday, for which a Gale Watch has 
been issued.

Outlook /Tuesday through Friday/...

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 10 ft. Chance of rain
showers. 

Tuesday Night: Strong winds with gusts up to 35 kt. Rough seas
up to 12 ft. Slight chance of rain showers. 

Wednesday: Strong winds with gusts up to 35 kt. Rough seas up
to 15 ft. 

Wednesday Night through Thursday: Strong winds with gusts up to
40 kt. Rough seas up to 16 ft. Slight chance of rain showers. 

Thursday Night: Moderate risk for gale force winds with gusts
up to 45 kt. Rough seas up to 16 ft. Chance of rain showers. 

Friday: gale force winds with local gusts up to 45 kt. Rough
seas up to 16 ft. Chance of rain showers. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 AM to 8 PM EDT Monday for 
     ANZ231>235-237.
     Small Craft Advisory from 8 AM Monday to 3 AM EDT Tuesday for 
     ANZ254>256.
     Gale Watch from Tuesday afternoon through Thursday afternoon 
     for ANZ255-256-282-283.

&&

$$

DISCUSSION...Dooley/McMinn
AVIATION...Dooley/McMinn
MARINE...Dooley/McMinn