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 031128
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
728 AM EDT Mon Aug 3 2026

.WHAT HAS CHANGED...
No significant changes.

&&

.KEY MESSAGES...

- A cold front brings the return of heavy rain and gusty winds 
Sunday night and Monday. Localized flash flooding possible. 

- After a quiet Tuesday unsettled weather returns mid week through 
the weekend with periods of showers and storms.

&&

.DISCUSSION...
KEY MESSAGE 1...A cold front brings the return of heavy rain and 
gusty winds Monday.  

An anomalously deep upper trough digging into the Ohio Valley will 
become cutoff as the broader longwave trough axis works its way 
slowly east. Its trough axis will cross over southern New England 
Monday night into Tuesday ushering in a much quiet and drier period. 
Before that, however, we'll be dealing with a very moist and dynamic 
system for the next 18-24 hours. This, as the shortwave and surface 
reflection pull copious amounts of moisture north into New England 
on strengthening SW flow (PWATs 2+ inches) with a 40-55 kt LLJ 
strengthening as it's core moves over the Cape and islands. 
Fortunately, even though BUFKIT soundings show 55kts down to about 
925mb, the low level inversion should keep the worst aloft. 
Regardless, it will be a gusty day, especially over southeast MA. 
While some brief stronger gusts can't be ruled out, they are more 
than likely to top out around 40 mph on Cape Cod. 

Regardless of its impact at the surface, said LLJ will certainly act 
as a strong forcing mechanism for our heavy rain. This together with 
divergence aloft/placement beneath the RRQ of an upper jet will lead 
to broad, deep layer ascent and widespread rain showers and 
thunderstorms. Continuing to expect an initial round of moderate to 
heavy rain showers this morning into the afternoon which has already 
begun to materialize. The atmosphere is primed for some heavy 
downpours and while we can't nail down exactly who will see these 
downpours, any convection would lead to a better chance of those 
higher rain rates hinted at by the HREF (low probability of as much 
as 1+/hr). 

There's unlikely to be a real break in the showers and embedded 
thunderstorms but any pockets of clearing skies between showers may 
lead to increased instability parameters and a better chance for one 
of these thunderstorms to become severe as a final source of forcing 
arrives in the evening in the form of a cold front. Any storms that 
do get going will be in an environment with 30-45 kts of 0-6km bulk 
shear meaning potential for organization and some damaging wind 
potential. 

When all is said and done (ending in western MA by 8pm, eastern MA 
by midnight) a widespread 0.5 to 1.5 inches of rain is expected. 
That being said, convective enhancement and potential for training 
thanks to boundary-parallel mean flow mean that localized areas 
could see significantly more, on the order of 3-4 inches. This 
amount, especially if it falls in a short period, may lead to street 
flooding and even isolated flash flooding situations. However, we 
don't expect a widespread flash flooding risk with this system. 

KEY MESSAGE 2...After a quiet Tuesday unsettled weather returns mid 
week through the weekend with periods of showers and storms.  

After a beautiful, mostly sunny, less humid day on Tuesday under 
high pressure ridging, unsettled weather returns Wednesday into the 
weekend. A broad mid level trough sets up over the eastern U.S. with 
several shortwaves rotating through the base of the broader trough 
and this will bring periodic rain and thunderstorm chances each day, 
especially in the afternoon/evening.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

12Z TAF Update: 

Today: Moderate confidence. 

IFR/LIFR in RA/+RA through the day. Embedded storms possible 
within the first few rounds of rain 12-21Z. Another round of 
scattered thunderstorms likely pushes through from west to east 
19Z-00Z ahead of the approaching cold front. Wind shear likely 
continues in the east/southeast terminals during the day. SW 
winds 10-20 kts with gusts 20-30 kts. Could see period in the 
afternoon that winds gust 25-35 kts for the east and especially 
SE terminals if we clear out before the early evening round of 
storms.

Monday night: High confidence. 

SHRA/TSRA will be pushing out of eastern terminals between 00-03Z
leaving VFR conditions with light W wind. 

Tuesday: High confidence. 

VFR. Winds 5-10 kts, first W then becoming SW after 18Z. 

KBOS Terminal...Moderate confidence in TAF. 

Expect steadiest precipitation between 14-18Z with intermittent
SHRA thereafter. Low confidence in TSRA, but thunder will be
possible for the duration of the day. 

KBDL Terminal...Moderate confidence in TAF.

Outlook /Tuesday through Friday/...

Tuesday through Tuesday Night: VFR. 

Wednesday through Wednesday Night: VFR. Slight chance SHRA.

Thursday through Thursday Night: VFR. Breezy. Slight chance
SHRA, slight chance TSRA.

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

&&

.MARINE...
Forecaster Confidence Levels...

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

Winds and seas increase into early this morning across the 
southern and eastern waters eventually increasing across the 
northern waters. Seas 5-9 ft for the outer coastal waters, 
especially south. 5-7 ft seas stretch into portions of the inner
souther waters. SW winds 15-20 kts with gusts around 30 kts. 
Can't rule out a few isolated gusts near Gale-force late 
morning-afternoon if winds mix down from the low level jet 
overhead. SCAs are in effect for all the coastal marine zones. 
Elevated seas will keep SCAs around through Tuesday for the 
southern waters.

A high surf advisory is in effect for the south coast and 
islands Tuesday. A strong 35-45 kt southerly low level jet will
help build waves 5-9 ft across the waters of RI and south of 
MVY-ACK Monday. Rough surf and strong rips are likely to linger 
into Tuesday. Will have to watch this as Tuesday is shaping up 
to be an ideal beach day.

Outlook /Tuesday through Friday/...

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

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

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

Wednesday Night: Winds less than 25 kt. 

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory until 9 PM EDT this evening for MAZ023-024.
RI...High Surf Advisory until 9 PM EDT this evening for RIZ006>008.
MARINE...Small Craft Advisory until 5 PM EDT this afternoon for ANZ230-
     236.
     Small Craft Advisory until 5 PM EDT this afternoon for ANZ231-
     251.
     Small Craft Advisory until 2 AM EDT Tuesday for ANZ232>234.
     Small Craft Advisory until 2 PM EDT Tuesday for ANZ235-237.
     Small Craft Advisory until 2 PM EDT Tuesday for ANZ250-254.
     Small Craft Advisory until 8 PM EDT Tuesday for ANZ255-256.

&&

$$

DISCUSSION...BW
AVIATION...BW/RM
MARINE...BW