Lexington Weather

Lexington, Massachusetts, USA

50°F

5/24/2025 12:11am

Lexington Conditions: Overcast
Temperature: 50.4°F / 10.2°C
Dew Point: 48.4°F
Relative Humidity: 93%
Wind: SSE 2 mph, 10-min avg: 2 mph, gust: 7 mph
Barometer: 29.75 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 221641
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1241 PM EDT Thu May 22 2025

.SYNOPSIS...
A late season Nor'easter will bring a cold windswept heavy rain
to the region today and tonight. Winds will gust between 40 and
50 mph along the coast and pockets of minor coastal flooding 
will be possible at the time of high tide. The steady rain will 
be over by early Friday morning, but a few lingering showers 
with unseasonably chilly temperatures will persist into 
Saturday. Drier weather with gradually moderating temperatures 
are on tap for Sunday and especially Memorial Day when parts of 
the region may finally see highs break 70 degrees.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
945 AM update...

No changes to the current forecast. Area of heavy rain lifting 
north along the south coast will continue to move northward 
across SNE this morning. Still looking at the peak of the rain
and wind occurring mid afternoon through early evening. Strong 
signal in the HREF with enhanced probs of > 1" in 3 hours across
RI and eastern MA. Expecting 1-2" of rainfall in a 6 hour period
this afternoon and evening at the nose of the easterly low level
jet as it lifts north across the region. This will impact the 
evening commute with areas of urban and poor drainage street 
flooding. Strongest winds also during this time with peak gusts 
to 55 mph possible over the Cape/Islands, 40-50 mph gusts along
the immediate eastern MA coast, and 30-40 mph gusts along the 
I-95 corridor. 

Previous discussion...


Key Messages:

* Widespread rain arrives this morning and becomes heavy during
  the afternoon/eve with nuisance street flooding possible

* ENE wind gusts of 40-50+ mph along the coast with pockets of
  minor coastal flooding during the evening high tide.

* Unseasonably cool with highs mainly in the 40s

Not much change to the ongoing forecast for today. Expecting a 
low pressure to approach southern New England from the south 
towards this evening. While the center of this low pressure 
should remain near Nantucket and the outer Cape, Rainfall will 
reach farther inland. Still thinking the heaviest rainfall will 
be across the eastern half of southern New England. It appears 
than most of our region should receive total rainfall of 1-2 
inches through daybreak Friday. HREF LPMM had peak totals closer
to 3 inches in spots towards the east coast of MA, which 
appeared reasonable. 

Given the duration of this storm, not anticipating any flash 
flooding. Poor drainage and urban flooding is more likely at the
most susceptible spots. We may need to keep an eye on area 
rivers though, especially some of the smaller ones. Will need to
see exactly where the heaviest rainfall occurs and how quickly 
it falls. This should be a soaking rainfall, which will only 
help alleviate some of the dryness we have across southern New 
England.

Besides the rainfall, there is a concern for some minor wind 
impacts. A potent low level jet (3-4 standard deviations above
normal) will provide the momentum for some gusty winds. A Wind
Advisory remains in effect for the eastern MA coast. Gusts as 
high as 45-55 mph are possible on Cape Cod and the islands, with
gusts up to 50 mph for the rest of the east coast. Gale Warnings
also remain in effect for all MA and RI coastal waters. 

A Coastal Flood Advisory continues along the coast for low-end
minor flooding potential with the evening high tide, when some
erosion and minor splashover is possible. Fortunately,
astronomical tides are on the lower side, which saves us from 
much bigger problems that would have arisen. 

Overall, the main impacts from this system still looks to be 
within a 12-hour period from noon to midnight.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Low pressure should pass near Nantucket and the outer Cape
tonight, reaching the Gulf of Maine for Friday. The majority of
the rainfall and wind impacts should be before midnight,
although some lingering showers are possible towards northeast 
MA. Winds will remain elevated longer across the eastern MA 
coastal waters. This low pressure will move farther from our 
region Friday, but still keep enough cyclonic flow across our 
region where scattered showers remain a possibility, especially 
during the afternoon hours.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Key Messages:

* Unseasonably cool Sat with a few showers, but not a washout 
* Mainly dry Sun/Mon & with many locales breaking 70 by Mon 
* A few showers Tue night/Wed if a low tracks far enough north
* Despite moderating temps they will remain a tad below normal

Details...

Saturday...

Anomalous closed upper level low will still be spinning in the
vicinity of Maine and the Canadian Maritime on Sat. Cyclonic
flow around this system will result in at least a scattered to
broken deck of clouds with a few passing showers. However,
the majority of the day will be dry but just unseasonably cool.
850T are only around 0C...so while some peeks of sunshine will
likely occur high temps will mainly be in the upper 50s to near 
60.

Sunday and Monday...

The closed upper level low that has been controlling our weather 
will finally lift northeast of the Canada Maritimes Sun and Mon.
At the same time, a ridge of high pressure will build in from
the west. The result will be mainly dry weather and moderating
temps. Highs should reach into the 60s on Sun and probably 
breaking 70 in spots on Monday /Memorial Day/.

Tuesday into Wednesday...

The next shortwave trough and its associated low pressure system 
will be approaching from the west by the middle of next week. 
However, northern stream energy may try to force the deeper
moisture and forcing south of our region. So while we may see a 
few showers Tue night/Wed...a lot of the guidance suggests this 
system may be a glancing blow/miss. It is way too early though 
to lock anything in and will just have to see how the models 
trend over the next few days. The high temperatures Tue and Wed 
will depend on the above, so thinking most likely outcome are
highs in the middle 60s to the lower 70s. Certainly a big
improvement from what we will experience the next few days, but
temperatures still likely to average a bit below normal into 
the middle of next week.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

18z TAFs: Overall high confidence in trends, but some
uncertainty in timing.

MVFR conditions in rain and fog will give way to more widespread
IFR conditions as we head through late afternoon and into
tonight. Potential for embedded TS near the south coast,
especially on Cape Cod and the Islands through late afternoon.
E/NE winds gust to 30kt inland and to 40-45kt along coast. In
addition, LLWS expected near ACK due to 40-50kt winds at 020.

Slow improvement late tonight into Friday as rain ends from 
southwest to northeast, but MVFR/IFR ceilings are likely to 
persist.
 
BOS TAF...High confidence.

BDL TAF...High confidence.

Outlook /Friday Night through Tuesday/...

Friday Night: Mainly MVFR, with local IFR possible. Chance
SHRA.

Saturday: Mainly MVFR, with local IFR possible. Breezy. Chance
SHRA.

Saturday Night: Mainly VFR, with areas MVFR possible. Slight
chance SHRA.

Sunday: Mainly VFR, with local MVFR possible. Breezy. 

Sunday Night through Monday Night: VFR. 

Tuesday: Mainly VFR, with areas MVFR possible. Slight chance
SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Friday: High confidence. 

Rain arrives across the southern coastal waters early this
morning, and across the eastern coastal waters by mid morning. 
Poor visibility in moderate to heavy rainfall at times. Increasing
winds as a low pressure moves across the waters late today into
tonight. A Gale Warning remains in effect for all waters for 
35-45 kts with seas 6-10 ft. Winds and seas slowly begin to 
diminish through tonight into Friday.

Outlook /Friday Night through Tuesday/...

Friday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers. 

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

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

Sunday through Monday Night: Winds less than 25 kt. 

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Wind Advisory until 11 PM EDT this evening for MAZ007-015-016-
     019.
     Coastal Flood Advisory from 6 PM to 11 PM EDT this evening for 
     MAZ007-015-016-019-022>024.
     Coastal Flood Advisory from 4 PM this afternoon to 7 PM EDT 
     this evening for MAZ020-021.
     Wind Advisory until 11 PM EDT this evening for MAZ022>024.
RI...Coastal Flood Advisory from 4 PM this afternoon to 7 PM EDT 
     this evening for RIZ006>008.
MARINE...Gale Warning until 1 AM EDT Friday for ANZ230.
     Gale Warning until 11 PM EDT this evening for ANZ231>235-237.
     Gale Warning until 11 PM EDT this evening for ANZ236.
     Gale Warning until 7 AM EDT Friday for ANZ250-251.
     Gale Warning until 1 AM EDT Friday for ANZ254>256.

&&

$$

SYNOPSIS...Belk/Frank
NEAR TERM...Belk/KJC
SHORT TERM...Belk
LONG TERM...Frank
AVIATION...JWD
MARINE...Belk/Frank