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 062345
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
745 PM EDT Thu Aug 6 2026

.WHAT HAS CHANGED...
No significant changes. Although it remains very warm into the 
weekend, the level of heat does begin to drop off so the current
thought is to not extend the Heat Advisory beyond Friday.

&&

.KEY MESSAGES...

- Heat and humidity continues into Friday, with only a few
  afternoon showers or thunderstorms.

- Cool front brings scattered storms Saturday. Less humidity
  levels and dry weather Sunday but daily shower/storm chances
  resume early to midweek.

&&

.DISCUSSION...
KEY MESSAGE 1...Heat and humidity continues into Friday, with 
only a few afternoon showers or thunderstorms.

Latest model guidance does not show much need for changes to the
forecast for the remainder of today and tomorrow. As typical
with convection, even hi-res models struggle with timing,
placement and coverage. We have already seen a few showers
develop across areas further east (ie: Boston area to the North
Shore) than was previously anticipated. With the SW flow, the
south coast sea breeze is moving northward and thus expect
shower chances to remain north of this boundary as the
afternoon/evening goes on. We do have a decent amount of Mixed
Layer CAPE (MLCAPE) on the order of 2000 J/kg, but mid level
lapse rates are very meager, so not expecting any substantial
thunderstorm development. Convection will wane with sunset. With
the very moist airmass, we will again see the development of
stratus and fog later tonight, especially across the southern
half of SNE. Like today, those clouds and fog will "burn" off
tomorrow morning. No real airmass change, though if anything, it
will be a degree or two warmer. 925mb temperatures today were in
the 23-24C range, and that rises to 25-26C on Friday. When
combined with dewpoints in the 70s, heat index (feels like)
temperatures will top out well into the 90s, if not low 100s.
Thus the Heat Advisory will continue. There will be a warm layer
aloft (above roughly 850mb/5000ft) that will act as a lid to
keep convection at bay. Though an isolated afternoon shower or
thunderstorm is possible, they should be more the exception and
likely contained to far western areas where the hilly terrain
will help focus convective development. Guidance is a little
unclear for Friday night, but we might see some late evening
convection move in from the west. Just kept with NBM PoPs
showing roughly 20-40% PoPs overnight for the CT River Valley
and points east. 



KEY MESSAGE2...Cool front brings scattered storms Saturday. 
Less humidity levels and dry weather Sunday but daily 
shower/storm chances resume early to midweek.

All in all a general sameness to the weather pattern day-by-day 
through Saturday, with warm temperatures in the 80s with very high 
humidity levels, to go along with daily shower and thunderstorm 
chances following the diurnal cycle. Saturday offers a better shot a 
a bit more thunderstorm coverage with a cool front, although the 
risk for organized severe weather looks minimal, kept in check by 
weak windfields aloft leading to deep layer shear magnitudes in the 
25-30 kt range and generally slower SWly storm motions. This front 
will offer somewhat lower humidity levels, basically knocking 
dewpoints down from current "oppressive" values in the low to mid 
70s to "humid" mid/upper 60s levels. Storms would be capable of 
lightning and heavy rain, with the strongest of those storms capable 
of frequent lightning and localized downdrafts capable of sporadic 
wind damage, but those should be a very small subset of the storms.  

Weak subsidence and marginally lower dewpoints could limit or 
mitigate shower/storm chances on Sunday, although still with the 
usual summer warmth. The risk for daily shower and thunderstorm 
chances also increases early to mid next week as the Northeast 
states become more influenced by a somewhat stronger belt of 
westerly midlevel flow. With stronger winds aloft with that comes a 
somewhat better chance for storms becoming strong/severe but the 
timing is still uncertain. 

Stayed fairly close to NBM forecast values during this period.

&&

.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.

SHRA/embedded TS in interior Southern New England expected to 
weaken/dissipate by 01z. VFR should then prevail for most TAFs,
but coastal stratus/mist to advance northward from the south
coast around 02-04z to PVD and then potentially as far north as
ORH/BDL. Latest guidance seems more pessimistic on stratus
making it north of there after 09z, so left TEMPO in for BOS 
for now. SW winds 5-10 kt.

Friday though Friday Night: High confidence overall but 
moderate on SHRA/TS timing. 

Stratus dissipates/retreats to the waters between 13-16z (later
Cape and Islands), to mainly VFR conditions. Risk for TSRA again
tomorrow coming in from NY but the start timing varies from 
as soon as 18-20z to as late as 03z. This will need some
refinement but best estimate is the 18-20z timing. Will likely 
also have stratus/fog return to PVD and the Cape airports Friday
night. SW winds 5-10 kt, though seabreezes return to eastern MA
coast again before turning SW ~00z.

KBOS Terminal...Moderate confidence. VFR should generally
prevail but possible MVFR stratus 09-12z near/south of BOS 
with a better chance toward OWD. Seabreeze should return again
Fri but be later (after 17z). 

KBDL Terminal...Moderate confidence. VCSH nearby terminal
through 01z, then trending VFR tonight, with possible early-
morning fog/stratus. Risk for TSRA again tomorrow but timing is
uncertain.

Outlook /Friday Night through Tuesday/...

Saturday: VFR. Breezy. Chance SHRA, chance TSRA.

Saturday Night through Sunday: VFR. Breezy. 

Sunday Night: VFR. 

Monday: VFR. Breezy. 

Monday Night: VFR. Slight chance SHRA.

Tuesday: VFR. Breezy. Chance SHRA, slight chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Friday... High Confidence.

No significant changes to the forecast. Overall weather pattern
shows a large area of high pressure off the east coast. This
will continue to produce a SW flow across the entire region into
the weekend. 

Outlook /Friday Night through Tuesday/...

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

Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers. 

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

Monday: Winds less than 25 kt. 

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT Friday for CTZ002>004.
MA...Heat Advisory until 8 PM EDT Friday for MAZ003>007-010>021-026.
RI...Heat Advisory until 8 PM EDT Friday for RIZ001>007.
MARINE...None.

&&

$$

DISCUSSION...Loconto/Nash
AVIATION...Loconto/Nash
MARINE...Loconto/Nash