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 110716
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
316 AM EDT Fri Sep 11 2026

.WHAT HAS CHANGED...

No significant changes to the forecast.

&&

.KEY MESSAGES...

- Plenty of sunshine with comfortable humidity today & Sat
  and highs in the 70s. Lows tonight in the 40s & 50s.

- Showers and possibly a few thunderstorms with brief torrential
  rainfall possible late Sat night into the first half of Sun. 
  Low probability for localized flash flooding. 

- Dry and seasonable Mon-Tue but a brief bout of summer warmth
  and humidity possible Wed and/or Thu ahead of a cold front.

&&

.DISCUSSION...

KEY MESSAGE 1...Plenty of sunshine with comfortable humidity 
today & Sat and highs in the 70s. Lows tonight in the 40s & 50s.

Large high pressure builds over the region today into Sat. This will 
result in plenty of sunshine and very pleasant September weather 
with comfortable humidity. Highs today and Sat will be well into the 
70s with much less wind than yesterday. Mainly clear skies, light 
winds, and a dry airmass in place will result in ideal radiational 
cooling conditions tonight. Low temps tonight will bottom out in the 
40s to the lower 50s...But middle to upper 50s in the urban centers 
of downtown Boston/Providence. 

KEY MESSAGE 2...Showers and possibly a few thunderstorms with brief 
torrential rainfall possible late Sat night into the first half of 
Sun. Low probability for localized flash flooding. 

High pressure moves off the coast for the second half of the 
weekend. At the same time...a shortwave and an associated warm front 
will approach from the southwest. This will result in quite the mid 
level instability burst. Showalter indices drop nearly 20 units to 
near or below zero inside about 12 hours. That rapid change in 
stability supports the development of a complex of showers and 
perhaps a few thunderstorms. This coupled with Pwats rising to 
around 2 inches support the potential for pockets of torrential 
rainfall. This will be dependent on where a meso-surface low tracks 
and sets up a boundary for enhanced convergence. This will of course 
be a nowcast/mesoscale type of forecast...but given the Pwat 
plume/low level boundary there is a low probability for localized 
flash flooding. Usually for this to occur...several things need to 
happen on the mesoscale but it is something we need to watch with 
the main concern near and south of I-90.

The timing still needs to be refined...but favoring late Saturday 
night into Sunday morning as to when the bulk of the rainfall 
occurs. Rainfall amounts are highly uncertain and potentially 
extremely variable. Perhaps just a tenth to half inch in many 
locations...but the potential exists for a very localized narrow 
band of 2-3"+ of rainfall in a short amount of time. The models that 
indicate this risk have it in a different locations too. And even if 
this occurs it may not end up in our forecast area. Nonetheless...it 
is something we certainly need to watch. It will be also become 
quite muggy by Sunday afternoon with highs in the 70s. 

KEY MESSAGE 3...Dry and seasonable Mon-Tue but a brief bout of 
summer warmth and humidity possible Wed and/or Thu ahead of a cold 
front.

High pressure builds back into the region Mon and Tue bringing dry 
and seasonable weather. High temps will mainly be in the upper 60s 
to the middle 70s with lows in the 40s and 50s. This high pressure 
system moves east of the region by the middle of next week. This may 
allow for a brief return of summerlike warmth/humidity sometime Wed 
and/or Thu. 

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...

Forecaster Confidence Levels...

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

06z TAF Update...

Today...High confidence.

VFR. NW winds 7-13 knots except becoming SW after 19z/20z towards 
the Cape and Islands.

Tonight...High confidence.

VFR. Calm/light NNW winds.

Saturday...High confidence.

VFR. S winds 6-12 knots except for sea breezes along much of the 
coast. 

KBOS Terminal...High confidence in TAF. Gradient should remain 
strong enough to keep winds NW today. However...sea breeze expected 
on Sat. 

KBDL Terminal...High confidence in TAF.

Outlook /Saturday Night through Tuesday/...

Saturday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA, slight chance TSRA, patchy BR.

Sunday: Mainly VFR, with areas IFR possible. Breezy. SHRA
likely, slight chance TSRA, patchy BR.

Sunday Night through Monday: VFR. Breezy. 

Monday Night through Tuesday: VFR. 

&&

.MARINE...

Forecaster Confidence Levels...

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

Today through Saturday...High confidence.

Large high pressure will be building over the waters today through 
Saturday. This will keep winds/seas below small craft advisory 
thresholds along with excellent visibility for mariners. 

Outlook /Saturday Night through Tuesday/...

Saturday Night: Winds less than 25 kt. Chance of rain showers. 

Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.
Rain showers likely, slight chance of thunderstorms, patchy
fog. Local visibility 1 to 3 nm.

Sunday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers. 

Monday through Monday Night: Winds less than 25 kt. Seas
locally approaching 5 ft. 

Tuesday: Winds less than 25 kt. 

&&

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

&&

$$

DISCUSSION...Frank
AVIATION...Frank
MARINE...Frank