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 201838
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
238 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.

- High pressure will yield mainly dry conditions and cool
  temperatures the first half of the week. Potential for an
  offshore coastal low late week. There is still uncertainty in
  the track and strength at this time.

&&

.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...High pressure will yield mainly dry conditions 
and cool temperatures the first half of the week. Potential for 
an offshore coastal low late week. There is still uncertainty in
the track and strength at this time. 

There is good agreement across model guidance with a fairly 
strong surface high shifting over Quebec Tuesday into late-week.
This will put the region under a cooler than normal airmass 
with consistent NE flow. This will yield cooler than normal 
highs in the 60s through the week. There is a low probability 
that a system just brushes southern New England Tuesday bringing
a chance for showers mainly confined to the immediate south 
coast and Cape/Islands.

Deterministic and ensemble guidance continues highlight potential 
for a slow moving offshore coastal storm developing Wednesday into 
late-week. There is a general consensus with an upper low and trough 
first tracking eastward across the upper mid-west, although cluster 
analysis does highlight some variance in the amplitude of the trough 
and track of the  low. As this pushes to the east coast, a coastal 
low develops in the Atlantic then tracking northward toward the 
northeastern coastline. As with most coastal storms this far out, 
there is still a notable amount of variance across guidance in how 
this low tracks and its strength. This will directly feed into the 
uncertainty in elements such as winds, rain chances/amounts, and 
coastal erosion/flooding concerns. 

With a strong high to the north and an incoming upper low, the 
pressure gradient will tighten Tuesday through the week. This will 
result in strengthening winds/gusts across the coastal waters, 
especially the southern waters in closer proximity to the stronger 
gradient. There is some question on how strong the gradient gets and 
where the strong part of the gradient positions and this will
likely depend on the track and strength of the low. All that 
said, ensemble guidance is signaling potential for gale force 
gusts for the southern waters. Strong gusts may develop as early
as Tuesday night, but more likely Wednesday morning. Strong 
winds are likely to stay as the coastal low tracks northward; 
however, the magnitude will depend more on the track and 
strength of the low itself which remains less certain at this 
time. For land, winds will be gusty as well although not as 
high in magnitude as the coastal waters(25-35 mph) Wed- late 
week. Cape and Islands will likely be on the higher range of the
gusts. If the low ends up tracking more west, periods of rain 
will be possible sometime in the Thursday to Sat timeframe.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

18Z 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 between 18z-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.

Timing of IFR onset remains somewhat uncertain, but is generally 
expected after 21z. Have hinted at this potential with SCT groups at 
IFR levels for the time being, at least through 05z. 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