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 121948
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
348 PM EDT Fri Jun 12 2026

.WHAT HAS CHANGED...
The slight risk (level 2 of 5) of severe weather today remains in 
effect for far western CT and MA. The chance of severe weather also 
remains low, but not zero, for eastern MA/RI.

&&

.KEY MESSAGES...

- Isolated to scattered storms possible through this evening. A
  few may be strong to severe. 

- Above normal temperatures continue this weekend, though
  humidity levels drop to more comfortable levels. 


&&

.DISCUSSION...
KEY MESSAGE 1...Isolated to scattered storms possible through  
this evening. A few may be strong to severe. 

Under a moist and unstable airmass, a mid-level shortwave trough 
moves over Quebec helping trigger showers and thunderstorms this 
afternoon and evening. No major changes from the previous forecast. 
Modest shear paired with the daytime heating helping build 
instability (MLCAPE 1000-2000 J/kg). Recent runs of high-res 
guidance have shown a range of isolated to scattered storms. 
Some of the CAMs continue to show a few storms firing off a sea 
breeze boundary in east southern New England. There is also a 
general consensus across guidance for storms to develop in 
western MA/CT ahead of the cold front early this evening, moving
eastward. Can't rule out a strong to severe storm or two with 
the greater risk in west and central portions of southern New 
England. Gusty, locally damaging winds and lightning are the 
main hazards. Brief downpours are also possible within any 
storms. Any remaining showers or storms push offshore by 
midnight. 


KEY MESSAGE 2...Above normal temperatures continue this weekend, 
though humidity levels drop to more comfortable levels. 

An anomalously warm airmass remains over the region this weekend 
with ridging aloft. This will support above normals highs well into 
the 80s with some low 90s. Despite the similar temperature readings 
from the last few days, it won't feel as sweltering as it has been 
Saturday. Dewpoints stay in the mid to upper 50s which will take out 
the humidity factor and provide some marginal relief. With ridging 
aloft, conditions stay dry for Saturday and a good portion of 
Sunday. Next chance for showers/storms returns later Sunday with 
moisture/humidity increasing later in the day. More on that in the 
next key message below.  


KEY MESSAGE 3...Showers and thunderstorms Sunday evening/overnight, 
but the risk for severe weather is low.

After another very warm to hot Sunday, a cold front will be 
progressing into and through Southern New England Sunday night, 
which will increase the risk for showers and thunderstorms. Midlevel 
flow aloft increases and supports increasing deep-layer shear 
magnitudes of around 35 to 40 kt. However it still looks like 
instability looks on the low side, both due to the time of day post-
sundown and lower dewpoints, which is a significant limiting factor 
to how strong any storms may get. Both CSU and NSSL machine-learning 
progs indicate low (< 10%) probs of severe weather for Sunday night. 
Still expect some thunderstorms to develop/move eastward into the 
night but the risk they produce severe weather seems low. Even how 
much rainfall we get from these storms is uncertain, despite 
elevated PWATs in the 1.5-1.8" range, as some of the global models 
(GFS/Canadian) simulate a convectively-driven subsynoptic low over 
the mid-Atlantic states which moves well offshore of Southern New 
England into the overnight. Were this to develop, it could greatly 
reduce how much rainfall we do get. Others, such as the ECMWF/its 
ensemble mean, generate about a quarter to half inch of rain 
areawide. Increased PoPs into the Categorical range between the 
02- 10z timeframe from west to east before drying out as cold 
front moves through.

KEY MESSAGE 4...Return to more seasonable temperatures and lower 
humidity levels for the early to middle part of next week, 
then turning more active again into Thursday. 

A cooler and much drier airmass then works into Southern New England 
Monday into Tuesday. Latest guidance shows 850 mb temps now dropping 
to around +8 to +10C, some 5 degrees C lower than today. Highs more 
into the 70s to low 80s with dewpoints plummeting into the mid 
40s to mid 50s, so also substantially less humid compared to 
prior days with full sunshine. Early next week looks like a 
great stretch of summer weather; temperatures do start to warm 
up again as we move into Wednesday but are still seasonable in 
the low to mid 80s with still tolerable humidity levels. 

More active weather looks to develop around Thursday or Thursday 
night, as a stronger disturbance aloft moves in and sweeps a cold 
front through Southern New England. This could bring a better shot 
at showers/storms, although it's still too early for specifics at 
this timeframe.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

18Z TAF Update:

Today: Moderate confidence.

VFR. Light onshore winds for north coastal terminals, with 
light W winds away from the coastal TAFs. A few rounds of TSRA 
could develop, first in the 18-00Z time period over eastern MA 
and RI terminals along the seabreeze boundary, but confidence in
coverage and placement is low. Then again a broken line of 
storms is possible in the 22z-04z period, diminishing as it 
moves east. 

Tonight...High confidence.

SHRA/TSRA exiting by 04z. VFR except near the Cape/Islands 
where MVFR visbys under BR may creep in off the waters. NW winds
5-10 kts. Winds shift to the NW 00-04Z. 

Saturday....High confidence.

VFR. NW winds around 8-12 kts.

KBOS Terminal...Moderate confidence in TAF. VFR. Could see a 
few TS develop 19-00z along the seabreeze boundary. Given the
low confidence in placement, messaged as a VCTS given the
boundary will be nearby. Low chance for another round of storms
from western southern new england to reach the terminal. By the
time it get east to the terminal, they are more likely to be
SHRA. 

KBDL Terminal...Moderate Confidence in TAF. VFR. Light W winds.
Becoming NW after 00Z. Isolated thunderstorms possible 22-01Z.

Outlook /Saturday Night through Wednesday/...

Sunday: VFR. Breezy. 

Sunday Night: Mainly VFR, with local MVFR possible. Breezy.
SHRA, isolated TSRA.

Monday: VFR. Breezy. 

Monday Night: VFR. 

Tuesday: VFR. Breezy. 

Tuesday Night: VFR. 

Wednesday: VFR. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Saturday Night...High confidence.

Seas generally 1-3 ft, except 3-4 ft across the far outer waters
through Saturday morning. Isolated to scattered showers perhaps
an isolated storm over the waters this evening. Otherwise, winds
remain below SCA levels.

Outlook /Saturday Night through Wednesday/...

Sunday: Winds less than 25 kt. 

Sunday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Rain
showers, slight chance of thunderstorms. 

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

Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. 

Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft. 

Tuesday Night: Winds less than 25 kt. 

Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT this evening for CTZ002>004.
MA...Heat Advisory until 8 PM EDT this evening for MAZ002>006-
     008>014-017-018-026.
     Air Quality Alert until 11 PM EDT this evening for MAZ017>024.
RI...Heat Advisory until 8 PM EDT this evening for RIZ001>004.
     Air Quality Alert until 11 PM EDT this evening for RIZ001>008.
MARINE...None.

&&

$$

DISCUSSION...Loconto/Mensch
AVIATION...Mensch
MARINE...Loconto/Mensch