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

Southeast Middlesex County, MA - Heat Advisory
- SEE ALL NEARBY ALERTS -

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 112333
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
733 PM EDT Thu Jun 11 2026

.WHAT HAS CHANGED...
Both the marginal risk (level 1 of 5) and slight risk (level 2 
of 5) of severe weather on Friday were pulled back a bit further
west; chance of severe weather is low but not zero for eastern 
MA/RI.

&&

.KEY MESSAGES...

- Heat and humidity continues through Friday before we get a break 
  in the humidity, even if not so much from the heat. 

- Afternoon and evening showers and thunderstorms are possible
  both Thursday and Friday, a few of which could be severe. 

- Above normal temperatures continue this weekend but with a
  little less humidity. Dry weather prevails until a risk for 
  showers and thunderstorms develops Sunday night, and a couple 
  could become strong.

- Cooldown to more seasonable temperatures with drier weather
  for early next week.

&&

.DISCUSSION...
KEY MESSAGE 1...Heat and humidity continues through Friday before we 
get a break in the humidity, even if not so much from the heat. 

Temperatures in the 80s to low 90s and dewpoints in the upper 60s to 
low 70s have brought a muggy feel to the air today under a very 
moist airmass (PWATs near 1.75"). 850 mb temps surging to near 20C 
today will persist through Friday under a building mid level ridge 
and this prolongs the bout of above normal heat/humidity through 
Friday. Those elevated dewpoints will make temps in the upper 80s 
and 90s feel more like the 90s to near 100 (in the CT valley). The 
exception will be along the coast, especially the east coast of MA 
where onshore easterly flow keeps temps more comfortably in the 70s 
to mid 80s. The Heat Advisory continues through Friday with low 
temperatures limited by the elevated dewpoints to the upper 60s/low 
70s. 

KEY MESSAGE 2...Afternoon and evening showers and thunderstorms are 
possible both Thursday and Friday, a few of which could be severe. 

The same heat and humidity mentioned above are contributing to 
2,000+ J/kg of CAPE across SNE this afternoon and that will be 
conducive to scattered thunderstorms this afternoon owing to a few 
mid level shortwaves providing enough lift as they slide overhead. 
Ample moisture and instability are available, but a limiting factor 
is minimal 0-6km bulk shear 20-25 kts in the area where the best 
forcing and instability are. That being said, given the magnitude of 
instability it should be enough to overcome the limiting shear 
values to produce a few strong storms, one or two of which could be 
severe. The main threat will be damaging winds with a batch of 
storms moving in from NY; this is where the greatest threat is. 
Another batch of showers/storms likely initialize along a seabreeze 
boundary over eastern MA this evening as well with a lesser severe 
risk. 

Friday we'll have a similar setup with not much change in the 
airmass (instability and shear specifically) as the broader mid
level shortwave approaches so modest height falls as well as an
approaching cold front and quasi- seabreeze boundary will 
provide some lift to kick off a few clusters of thunderstorms. 
The first to see storms will likely be eastern MA and RI where 
that quasi- seabreeze boundary/onshore flow will likely help 
initialize some storms by mid afternoon. An approaching cold 
front from NY will also be moving through midnight which will 
lead to a broken line of storms from west to east 7pm-midnight; 
however, we will be losing our diurnal heating early in that 
period so instability and severe potential will be decreasing 
quickly; best chance of severe weather is in western MA and CT 
where we have placed a Slight (level 2 of 5) severe risk. 

KEY MESSAGE 3...Above normal temperatures continue this weekend but 
with a little less humidity. Dry weather prevails until a risk for 
showers and thunderstorms develops Sunday night, and a couple could 
become strong.

While still very warm to hot on Saturday, we should see a bit less 
humidity compared to the past couple days. Dry weather should 
prevail as shortwave ridging governs, with areas along the MA east 
coast and around Narragansett Bay. Highs should again reach well 
into the 80s to low 90s but with dewpoint temperatures in the upper 
50s/near 60 compared to the upper 60s/low 70s, it should be a 
somewhat drier heat. Under shortwave ridging, the risk for afternoon 
storms also looks to be mitigated with dry weather anticipated. 

Southwest flow resumes on Sunday and with it comes a bit of an 
increase to humidity level but not to the extent of today or Friday. 
We'll also be waiting on an approaching cold front to trigger 
showers and thunderstorms, and while the exact timing varies, 
there's some general agreement on it being a later arrival (after 5 
PM) into western New England. Midlevel flow increases Sunday in 
response to the approaching shortwave aloft with WSWly 0-6 km 
shear vector magnitudes around 35 to 45 kt, supportive of severe
weather potential. The issue is more tempered instability with 
the later-day timing and dewpoints being on the lower side, with
better instability more restricted to the northern mid-Atlantic
region where SPC has delineated a 15% probability for severe 
storms. PoPs increase into the Likely range for showers and 
thunderstorms Sunday evening, but if storms can produce severe 
weather is still a question mark, which will hinge on either an 
earlier timing or higher forecast dewpoint temperatures. 

KEY MESSAGE 4...Cooldown to more seasonable temperatures with drier 
weather for early next week.

Cooldown to temperatures for early next week, as the offshore 
passage of the cold front allows more of Southern New England to 
become governed by cooler cylonic flow aloft. 850 mb temps drop to 
around the +10 to +12C range versus the +16 to +18C range, 
supporting highs in the 70s to low 80s under sunny conditions to go 
along with comfortable humidities. Dry weather also prevails through 
Tuesday until a wave of low pressure in SW flow brings a risk for 
showers and thunderstorms around midweek.

&&

.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: Moderate confidence. 

An ongoing cluster of TSRA over central NY near BGM/SYR offers
best chance at TSRA between 01-04z, with best chance at BDL and
and into ORH/PVD; used PROB30s given the late time of day. A
low risk exists elsewhere but too low confidence to include in 
the TAF. These showers/storms also could cast question when/if 
IFR stratus develops over the Cape and Islands; offered 07-08z 
for development but this is more uncertain and it could remain 
VFR most of the night. Light west winds, with seabreeze at BOS 
persisting thru 03z. 

Friday: Moderate confidence.

VFR. Light onshore winds developing, with light W winds away
from the coastal TAFs. A few rounds of TSRA developing, first 
in the 18-00Z time period over eastern MA and RI terminals, then
again a broken line of storms is possible in the 23z-06z 
period. Both are too low-confidence to include in TAFs.

Friday night...High confidence. 

SHRA/TSRA exiting by 06z. VFR. NW winds 5-10 kts. 

KBOS Terminal...Moderate confidence in TAF. E/NE winds should
persist thru 03z Friday before turning light westerly. Two
periods of possible TS: one after 03z until 07z Fri, with 
another around 16-23z Fri as seabreeze develops. Neither of 
these periods offer high enough confidence to include in the TAF
as yet. 

KBDL Terminal...Moderate Confidence in TAF. Better chance at
TSRA around 01-03z as line of storms moves in from the
Berkshires. Should be VFR thereafter with light W winds but turn
light southerly tomorrow, and another round of late-day TS
possible.

Outlook /Friday Night through Tuesday/...

Saturday: VFR. Breezy. 

Saturday Night: VFR. 

Sunday: VFR. Breezy. 

Sunday Night: VFR. Breezy. Chance SHRA, slight chance TSRA.

Monday: VFR. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Friday night...High confidence.

Seas 2-4 feet for the majority of the waters except 3-5 feet
across the southern outer waters tonight. SW winds increase to 
15-25 kt with gusts as high as 30 kts. SCA conditions continue 
for the southern waters today before gradually subsiding by the
late evening. Seas decrease to 1-3 ft by Friday and continue
into Friday night. Isolated to scattered showers and 
thunderstorms are possible Thursday night into Friday morning
then again Friday evening into Friday night. 

Outlook /Friday Night through Tuesday/...

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

Saturday through Sunday: Winds less than 25 kt. 

Sunday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Rain showers likely, slight chance of thunderstorms. 

Monday: Winds less than 25 kt. Chance of rain showers, slight
chance of thunderstorms.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT Friday for CTZ002>004.
MA...Heat Advisory until 8 PM EDT Friday for MAZ002>006-008>014-017-
     018-026.
     Air Quality Alert until 11 PM EDT this evening for MAZ013-
     016>024.
     Air Quality Alert from 11 AM to 11 PM EDT Friday for 
     MAZ017>024.
RI...Heat Advisory until 8 PM EDT Friday for RIZ001>004.
     Air Quality Alert until 11 PM EDT this evening for RIZ001>008.
     Air Quality Alert from 11 AM to 11 PM EDT Friday for 
     RIZ001>008.
MARINE...Small Craft Advisory until 8 PM EDT this evening for 
     ANZ254>256.

&&

$$

DISCUSSION...Loconto/BW
AVIATION...Loconto/BW
MARINE...Loconto/BW