Old Res Weather

Lexington, Massachusetts, USA

35°F

2/16/2025 7:17pm

Lexington Conditions: Overcast
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 121918
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
318 PM EDT Thu Mar 12 2026

.WHAT HAS CHANGED...
Adjusted snowfall for tonight, although much of this should 
fall on grassy, non-paved surfaces. Confidence continues to grow 
in the likelihood for at least some wind headlines Saturday. In 
addition, confidence also increasing that a strong storm system
will bring a period of heavy rain along with potentially strong
to damaging wind gusts very late Sunday night into Monday night. 
River and small stream flooding is likely from this system given
heavy rain and additional snow melt in northern New England.

&&

.KEY MESSAGES...

- Light rain changes to a mix of rain/sleet and then to wet snow
  into early tonight. Reduced visibilities likely during the
  evening commute. Minor accumulation (up to 2", locally more 
  possible) but pavement should be mostly wet.

- Strong westerly wind gusts of 35-55 mph on Sat...Wind Headline 
  will likely be needed at least for parts of the region.

- Inland runner brings a period of heavy rain, strong winds, and
  unseasonably mild temps very late Sun night into Mon night.  
  Some river and small stream flooding is likely too.

- Turning much colder with mainly dry weather Tue through Thu.


&&

.DISCUSSION...
KEY MESSAGE 1...Light rain changes to a mix of rain/sleet and
then to wet snow into early tonight. Reduced visibilities 
likely during the evening commute. Minor accumulations, but 
pavement should be mostly wet.

Colder air continues to overspread southern New England, leading
to rain changing to snow into this evening. Not expecting much
from this snowfall as cloud bases are rather high. Our warmth
the past few days will also play a role, keeping pavement
temperatures likely high enough to be just wet. The exception
may be across portions of southeast MA, which could see local
accumulations around 1". It's a low probability for much more
than that.

Confidence in specific accumulations for specific locations is 
not especially high. Adjustments may become necessary in the
short-term as this event unfolds. Since this is Mid March,
snowfall this time of year is dependent upon time of day and
precipitation rate. Not expecting much in terms of heavy
precipitation, but the timing is still the largest question
since that also relates to temperatures.

Even though low temperatures drop to around 25-30 degrees
tonight, the risk for black ice looks minimized by strong
drying/evaporation. 

KEY MESSAGE 2...Strong westerly wind gusts of 35-55 mph on Sat. 
Wind headlines will likely be needed at least for parts of the
region. 

Low pressure will be lifting northeast into the Canadian
Maritimes on Sat. The result will be modest cold air advection
aloft and an 850 mb jet on the order of 35 to 50 knots. Very
steep low level lapse rates coupled with the increasing March
sun angle will result in much of this mixing down to the
surface. Therefore, expect westerly wind gusts of 40 to 55 mph
at times with wind Headlines likely being needed for much of 
the region. A fair amount of sunshine should still allow high 
temps to reach well into the 40s, but it will feel colder given
the strong winds. 

KEY MESSAGE 3...Inland runner brings a period of heavy rain,
strong winds, and unseasonably mild temps very late Sun night 
into Mon night. Some river and small stream flooding is likely 
too.

The long range model guidance is in fairly good agreement in
amplifying shortwave energy forming a deep anomalous upper
trough over the Great Lakes. This induces a meridional upper
level flow into southern New England which will result in an
unseasonably mild airmass into the region. The NAEFS guidance 
is showing both the LLJ and Pwat plume 3-4 standard deviations 
above normal, which is often a signal for a potentially
significant event. Given these ingredients, the model guidance
is indicating the potential for a widespread 1-2" of rain with 
localized 3"+ amounts not out of the question especially if 
there are any convective elements involved. And there is some 
elevated instability, so certainly the risk for at least
isolated thunder. The two big concerns revolve around the
potential for some river and small stream flooding and a period 
of strong to perhaps damaging southerly wind gusts. We will
discuss more below.

A lot of the MMEFS guidance indicates that this expected
rainfall coupled with recent river rises from snowmelt will push 
several of our points into flood. In addition, there is still a 
fair amount of SWE left in the snowpack across the mountains of 
northern New England. Given strong southerly flow and
anomalously high temps/dewpoints advecting all the way up
there...additional snowmelt and runoff will also tend to push
river levels higher. The other concern will be a period of
strong to potentially damaging southerly wind gusts. These
events are often difficult to forecast even in the very short 
term given the inversion. However, given the potential for temps 
to break 60 and global guidance showing a southerly LLJ 3-4
standard deviations above normal there is concern sometime Mon
and/or Mon night. Certainly a decent shot at Wind Advisory 
criteria for parts of the region and even a low risk for High 
Wind Warning criteria. Something to watch in the coming days.

KEY MESSAGE 4...Turning much colder with mainly dry weather Tue 
through Thu.

Behind this strong system...the long range guidance is in very good 
agreement in much colder but mainly dry weather in the Tue through 
Thu time frame. Highs will mainly be in the 40s Tue and Thu, but
many locations may struggle to break 40 for highs on Wed. 

&&

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

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

This Evening: Moderate confidence.

Mainly VFR, with areas MVFR in showers. Rain transitions to snow
during the evening push most likely, but doesn't linger long. 

Rest of Tonight: High confidence. 

Rapid improvement to VFR from west to east. By late evening,
just about all of southern New England should be VFR. Could be
closer to midnight for the Cape and islands. NW winds around 10
kt with occasional gusts to 20 kt. Even though temperatures 
will be subfreezing, rapid drying should limit any freeze-up on 
runways.

Friday: High confidence. 

VFR, though with increasing midlevel clouds late in the day. NW
winds become light and then shift to SW around 5-10 kt.

Friday Night: High confidence. 

Mainly VFR. Areas MVFR in rain and snow showers across northern
MA. Increasingly gusty S winds expected.

KBOS Terminal...Moderate confidence. Rain mixed with PL then 
brief SN. visibilities 2-4 SM in wintry precip, although 
runways should be wet. Rapid VFR improvement by late evening.

KBDL Terminal...Moderate confidence. Light snow developing by 
21Z, but should be over by 13/00Z. Mainly VFR, expected for
brief MVFR in precipitation late this afternoon and early
evening.

Outlook /Saturday through Tuesday/...

Saturday: VFR. Strong winds with gusts up to 45 kt. 

Saturday Night: VFR. Windy with gusts up to 35 kt. 

Sunday: VFR. Breezy. 

Sunday Night: Windy with gusts up to 35 kt. Chance RA, chance
FZRA.

Monday: Strong winds with gusts up to 45 kt. RA, slight chance
TSRA.

Monday Night: Strong winds with gusts up to 45 kt. RA.

Tuesday: Breezy. Slight chance RA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Rough seas linger across the outer coastal waters into Friday
morning. Winds expected to briefly diminish Friday afternoon,
before increasing once more from the south Friday night.

Outlook /Saturday through Tuesday/...

Saturday: Moderate risk for gale force winds with gusts up to
35 kt. Rough seas up to 11 ft. 

Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Local rough seas. 

Sunday: Winds less than 25 kt. 

Sunday Night: Low risk for gale force winds with gusts up to
35 kt. Local rough seas. Chance of rain. 

Monday: gale force winds with local gusts up to 45 kt. Rough
seas up to 14 ft. Rain, slight chance of thunderstorms. 

Monday Night: Moderate risk for gale force winds with gusts up
to 45 kt. Rough seas up to 15 ft. Rain. 

Tuesday: Strong winds with local gusts up to 30 kt. Rough seas
up to 13 ft. Chance of rain. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 10 AM EDT Friday for ANZ235-237-250-
     256.
     Small Craft Advisory until 4 PM EDT Friday for ANZ254-255.

&&

$$

DISCUSSION...Belk/Frank
AVIATION...Belk/Frank
MARINE...Belk/Frank