Lexington Weather

Lexington, Massachusetts, USA

67°F

7/17/2026 12:56am

Lexington Conditions: Smoke, Clear
Temperature: 66.6°F / 19.2°C
Dew Point: 58.8°F
Relative Humidity: 76%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.84 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 162336
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
736 PM EDT Thu Jul 16 2026

.WHAT HAS CHANGED...
No significant changes have been made to the forecast.

&&

.KEY MESSAGES...

- A few brief spot showers possible across northern MA into mid-
  evening. Otherwise...dry and pleasant through Fri night outside
  of the wildfire smoke this evening. Lows mainly in the 50s to the 
  lower 60s. Highs Fri mainly in the lower to middle 80s. 

- Chances for beneficial showers and thunderstorms on the uptake for 
  Saturday PM into the overnight period.

- A cooler start to the work week with unsettled conditions
  through the middle of next week.

&&

.DISCUSSION...
KEY MESSAGE 1...A few brief spot showers possible across northern MA 
into mid-evening. Otherwise...dry and pleasant through Fri night 
outside of the wildfire smoke this evening. Lows mainly in the 50s to 
the lower 60s. Highs Fri mainly in the lower to middle 80s. 

A cold front will cross the region this evening. However...the lack 
of low level moisture coupled with the main shortwave forcing 
passing to our north will keep most of us dry. A few brief spot 
showers may survive into northern MA and perhaps the remote risk for 
a rumble of thunder in far northeast MA. Otherwise...generally a 
dry/very pleasant weather through Friday night. We will have to deal 
with some more smoke moving into the region through late 
afternoon...But the worst of it will likely stay to our southwest. 
And the good news is that it will get shoved into the mid-Atlantic 
after midnight and will not be an issue for Fri.

High pressure builds across the region on Friday behind tonight/s 
cold frontal passage. This high pressure system will shift east of 
us Friday night...But we will maintain dry/pleasant weather. Highs 
on Friday will mainly be in the lower to middle 80s with plenty of 
sunshine and comfortable humidity. Lows tonight and Friday night 
will mainly be in the 50s to the lower 60s with middle 60s in the 
urban heat island of Boston. 

KEY MESSAGE 2...Chances for beneficial showers and thunderstorms on 
the uptake for Saturday PM into the overnight period.

Chances for showers and thunderstorms begin to increase heading into 
the weekend as a surface low approaches Saturday, bringing prolonged 
southwesterly flow and surging PWATs. Latest guidance suite has 
increased confidence in PWATs over 2.0", with some as high as 3.0", 
which lends favor to some heavy downpours developing overnight. 
ECMWF and CMC ensembles indicate a 60-80% chance of at least 0.5" of 
QPF (mostly across the southern coastal areas and up into central CT 
and RI), while the GFS ensemble is trending those higher percentiles 
off our southern shores and further north into northern New England. 
Southern New England is currently in a Marginal (1/4) risk for flash 
flooding, but discussion has started with neighboring offices (and 
will continue with the next forecast cycle) on potentially 
increasing that risk to a Sight (2/4), particularly across the 
southern coastal areas of CT and RI given the relatively high 
consensus in the model guidance that some heavier bands could 
develop across those areas.

Instability profiles continue to look relatively weak, but CSU 
Machine Learning probabilities continue to indicate low (5-15%) 
chances that some storms could turn severe.

KEY MESSAGE 3...A cooler start to the work week with unsettled 
conditions through the middle of next week.

A cooler airmass moves in Sunday once the cold front pushes 
offshore, with temperatures making a return to seasonable norms... 
in the low to mid 80s through at least the middle of next week. A 
brief spell of drier conditions is possible Monday as high pressure 
builds somewhere over the Appalachian region. Chances for showers 
then increase again for the middle of next week as a surface low 
moves east across Ontario and a trailing cold front sweeps through 
the mid-Atlantic region into New England.

&&

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

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

00z TAF Update...

Tonight through Friday night...High confidence.

W wind gusts 25+ knots diminish this evening. NW winds 10 knots
or less overnight into Friday morning before they shift to the 
SW by mid-late Friday afternoon. A few hours of sea breeze 
conditions are also possible Friday afternoon along portions of 
the immediate coast. 

KBOS Terminal...High confidence in TAF.Improving VSBYs as smoke
decreases. Improving to VFR by 06z. 

KBDL Terminal...High confidence in TAF. We may see some MVFR vsbys 
flirt with the terminal this evening before pushing southwest. 

Outlook /Saturday through Tuesday/...

Saturday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA, chance TSRA.

Saturday Night: MVFR/IFR conditions possible. Windy with local
gusts up to 30 kt. SHRA, slight chance TSRA.

Sunday: VFR. Breezy. 

Sunday Night through Monday Night: VFR. 

Tuesday: Mainly VFR, with local IFR possible. Breezy. Chance
SHRA, chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Tonight through Friday night...High confidence.

Gusty near shore small craft W wind gusts will diminish this evening 
and shift to the NW behind the cold front. Otherwise...high pressure 
builds in from the west behind this evening/s cold front keeping 
winds/seas below small craft advisory thresholds. 


Outlook /Saturday through Tuesday/...

Saturday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Seas locally approaching 5 ft. Chance of rain
showers. 

Saturday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Seas up to 5 ft. Rain showers, slight
chance of thunderstorms. 

Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. 

Sunday Night: Winds less than 25 kt. Areas of rough seas. 

Monday: Winds less than 25 kt. Seas up to 5 ft. 

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

Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas. Chance of rain showers, slight
chance of thunderstorms.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Air Quality Alert until midnight EDT tonight for CTZ002>004.
MA...Air Quality Alert until midnight EDT tonight for MAZ002>024-
     026.
RI...Air Quality Alert until midnight EDT tonight for RIZ001>008.
MARINE...Small Craft Advisory until 8 PM EDT this evening for 
     ANZ230>237-250-251-254>256.

&&

$$

DISCUSSION...Frank/McMinn
AVIATION...Frank/FT
MARINE...Frank/McMinn