Old Res Weather

Lexington, Massachusetts, USA

35°F

2/16/2025 7:17pm

Lexington Conditions: Few Clouds
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 211822
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
222 PM EDT Tue Jul 21 2026

.WHAT HAS CHANGED...
No significant changes sine last forecast update.

&&

.KEY MESSAGES...


- Widespread showers and thunderstorms this afternoon and evening.


- Another round of showers and thunderstorms possible Wednesday
  afternoon

- Seasonable temperatures and comfortable humidity returns with
  dry conditions for the second half of the week.


&&

.DISCUSSION...

KEY MESSAGE 1... Widespread showers and thunderstorms this afternoon 
and evening.

Shortwave energy moving over the northeast will support a period of 
widespread showers and thunderstorms this afternoon and evening. 
Moderate instability to the tune of 750-1000 J/kg of MUPCAPE and 
high PWATs near 2" will support isolated to scattered areas of 
torrential rainfall with embedded thunder and widespread
moderate showers elsewhere. There is a low-risk for some storms
to be strong to severe with potentially damaging wind gusts. 
Relatively strong wind fields by July standards should mitigate 
the overall flooding threat with mid-level flow around 30 
knots supporting faster moving storms. However, we'll be on the
looking for any training areas of torrential rain that could 
lead to flooding in urban or poor drainage areas. Expect the 
greatest shower and thunderstorm activity across eastern MA and 
RI between roughly 5PM and 1AM. Shower and thunderstorm 
activity should wane overnight as stronger forcing shifts east 
of southern New England.

KEY MESSAGE 2... Another round of showers and thunderstorms 
possible Wednesday afternoon

Showers and thunderstorms return tomorrow afternoon with instability 
increasing in response to increased moisture. Dewpoints in the low 
to mid 70s may support SBCAPE values up to 1500 J/kg. Instability 
will depend greatly on how much heating we get early tomorrow. The 
amount of heating we get early will depend on how much clearing 
occurs between tonight and tomorrow morning. 12Z HREF guidance 
suggests enough heating to support showers and thunderstorms across 
eastern CT, MA, and RI during the mid-afternoon hours between 4 and 
8PM. Shear will be modest with roughly 20-25 knots in the 0-6km 
layer. Overall severe threat is low, but a few isolated strong 
to severe storms will be possible as a cold front pushes through
the region. A cooler/drier air mass settles over the region 
Wednesday night into Thursday with dewpoints falling to the 
upper 50s/low 60s. This should support a more comfortable day on
Thursday.

KEY MESSAGE 3...Seasonable temperatures and comfortable 
humidity returns with dry conditions for the second half of the 
week.

As the cold front finally pushes offshore Thursday, the upper level 
trough over Quebec also pushes northeast into the Labrador Sea and a 
high pressure system begins to build over the Great Lakes. A drier 
airmass will be ushered into southern New England Thursday in the 
wake of the cold front, with dewpoints dropping into the mid to 
upper 50s, leading to much more comfortable feeling temperatures. 
925mb and 850mb temperatures drop to near 16C and 10C, respectively, 
for the second half of the week, but intense sunlight and mostly 
clear skies will keep temperatures seasonable... roughly 80-85 
through at least Sunday. Rain chances don't look to make a return 
until later Sunday evening, possible Sunday night into Monday, as 
south-southwesterly flow becomes more dominant and dewpoints begin 
to increase.


&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...

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

18Z TAF Update: 

Through 00Z...Moderate confidence. 

Scattered showers from 18-21Z increasing in coverage and
intensity between 21-00Z with -TSRA possible. VFR ceilings/vsbys
deteriorating to MVFR. Steady south winds from 10-15 knots with
gusts to 25 knots. 

Tonight...Moderate confidence.

TSRA/+TSRA mainly between 00-03Z with ceilings falling to
MVFR/IFR levels. Expect SHRA/TSRA to wane between 03-06Z. IFR
conditions prevail thereafter with south/southwest winds around
10 knots. 

Tomorrow... Moderate confidence.

IFR ceilings scatter out to VFR across the interior with some
IFR/MVFR ceilings lingering over The Cape/Islands terminals into
the afternoon. Showers and thunderstorms possible after 18Z,
mainly across eastern MA and RI. Low confidence in intensity and
coverage of showers. Southwest winds 10-15 knots with some gusts
to 25 knots possible.

Tomorrow Night...High Confidence. 

Any afternoon SHRA/TSRA wanes after 00Z with VFR conditions
thereafter. Southwest winds shift to light out of hte northwest
from 5-10 knots behind a passing cold front. Expect the wind
shift around 06Z Thursday. 

KBOS Terminal...Moderate confidence in TAF. 

Lower confidence in shower coverage and intensity between
18-21Z. Confidence in SHRA increases around 21Z with moderate to
high confidence in TSRA near the terminal between 00-03Z, though
TSRA could be observed as early as 21-00Z.  

KBDL Terminal...Moderate confidence in TAF.

Highest chances for TSRA between 21-00Z.

Outlook /Thursday through Sunday/...

VFR. 

&&

.MARINE...
Forecaster Confidence Levels...

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

Tonight through Wednesday night

Gusty south/southwest winds over the coastal waters tonight with
near, but slightly below gale force gusts expected. Small Craft
Advisory remains in effect for 25-30 knot wind gusts and 6-10
foot seas over the outer marine zones. Highest waves expected
over the south coastal waters. Showers and thunderstorms
expected this afternoon and overnight.

Strongest winds come down to 20-25 knots for tomorrow with
continued steady 15-20 knot southwest flow during the day
tomorrow. A cold front crosses the waters tomorrow night
resulting in a wind shift to t he northwest. This will be
followed by more tranquil conditions to end the week. 



Outlook /Thursday through Sunday/...

Thursday: Winds less than 25 kt. Areas of rough seas. Chance of
rain showers, slight chance of thunderstorms. 

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

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

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

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory from 6 AM Wednesday to 8 PM EDT Thursday 
     for MAZ020>024.
RI...High Surf Advisory from 6 AM Wednesday to 8 PM EDT Thursday 
     for RIZ006>008.
MARINE...Small Craft Advisory from 8 PM this evening to 8 PM EDT 
     Wednesday for ANZ231>235-237-250-254>256.

&&

$$

DISCUSSION...McMinn/RM
AVIATION...RM
MARINE...McMinn/RM