Lexington Weather

Lexington, Massachusetts, USA

13°F

1/23/2025 5:55am

Lexington Conditions: Mostly cloudy
Temperature: 13.3°F / -10.4°C
Dew Point: 4.5°F
Relative Humidity: 67%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 30.34 in Falling Slowly
Visibility: 10 miles
Snow Today: 0.0 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 162047
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
347 PM EST Thu Jan 16 2025

.SYNOPSIS...
A weak low pressure system will bring a period of light snow showers 
tonight, mainly for areas near the south coast, Cape and 
islands. Temperatures then moderate Friday, and especially by 
Saturday, ahead of an approaching cold front. This cold front 
will bring a period of mainly rain showers later Saturday into 
Saturday evening. Dry weather should prevail for the first part 
of Sunday. However, a low pressure passing by offshore will 
likely bring a period of snow or rain changing to all snow late 
Sunday into early Monday. This will be followed by an arctic 
outbreak later Monday into Wednesday with below zero wind 
chills.

&&

.NEAR TERM /THROUGH TONIGHT/...
Key Messages:

* Scattered flurries/light snow showers mainly along the south 
  coast Thursday night. 

A mid-level trough pushes eastward this evening. Still looking
like weak synoptic support, and the latest guidance suite has
trended even weaker. Looking at a few flurries across the Cape
and islands this afternoon. More widespread light snowfall
should arrive this evening across southeast MA, and perhaps
briefly as far north as Boston, and as far west as the I-95
corridor between Boston and Providence. This snowfall should 
move offshore after midnight, but could linger neat the outer
Cape and Nantucket towards sunrise. Flurries most likely 
elsewhere.

Snowfall expected to be generally up to an inch for most, with
perhaps up to 2 inches locally towards the outer Cape and
Nantucket.

Below normal temperatures continue.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
Key Messages:

* Trending above normal and drier

Weak high pressure takes over during this portion of the
forecast. Winds gradually turn SW as this high pressure moves
offshore, and increases as a cold front approaches from the
west. Should be plenty of sunshine for most, but the Cape and
islands may still have some lingering clouds through Friday 
morning. The mainly clear skies are expected to be short-lived,
with increasing clouds Friday night ahead of a warm front. 

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Key Messages...

* Turning Milder/Breezy Sat with highs well into the 40s/near 50
* A round of rain showers later Sat into Sat evening
* Period of snow or rain changing to snow late Sun into early Mon 
* Arctic Outbreak later Mon into Wed with below zero wind chills

Details...

Saturday...

A ridge of high pressure off the mid-Atlantic coast will continue to 
move further east and away from the region Sat. At the same time...a 
cold front will be approaching from the west. This will result in 
the development of gusty southerly winds. 925T moderate to above 0C 
and with good mixing expect highs to reach well into the 40s to near 
50 despite an abundance of clouds. The best chance of reaching 50 
will be on the coastal plain. We think the shower threat will hold 
off until mid-late afternoon.

As the shortwave and associated pre-frontal trough approaches from 
the west the forcing for ascent will increase later Sat into Sat 
evening. Thinking is that a period of rain showers is most likely in 
the mid-late afternoon into the evening hours. Ptype will generally 
be all liquid given the warm boundary layer temps. Perhaps a touch 
of wet snow across the highest terrain along the east slopes of the 
Berks...but little if an accumulation/impacts expected.

Sunday into Monday...

Although the cold front will have crossed the region by daybreak 
Sun...it will take some time for the colder air to work into the 
region. So we expect highs to reach the upper 30s to the middle 40s 
on Sun with the mildest of those readings in the RI/SE MA region. 
The first part of Sun will be dry with partial sunshine...but that 
will likely change later Sun into early Mon which we will discuss 
below.

The main forecast challenge will revolve around an anafrontal wave 
of low pressure that will develop in the cold front. This will 
likely bring a period of snow or rain changing to snow late Sun into 
early Mon. There is still considerable spread on how close this wave 
of low pressure tracks in the vicinity of southern New England. The 
CMC model seems to be a west outlier...while the ECMWF is more of an 
east outlier. That being said...most of the 00z guidance suite 
indicates at least a period of snow or rain changing to snow over 
this time period for a good portion of the region. While this does 
not look like a major storm...accumulating snow is certainly 
possible for some locations. 

Later Monday into Wednesday...

The GEFS/EPS/CMC ensembles are in very good agreement in an Arctic 
Outbreak later Mon into Wed. A -EPO will result in strong ridging 
into northwest Canada and Alaska...allowing for the delivery of 
arctic air across the central/eastern U.S. given cross polar flow. 
850T drop to between -24C/-25C across the region. This will result 
in overnight lows mainly in the single digits Mon night and Tue 
night with some below zero readings possible too. Highs Tue and Wed 
may not reach 20 in many locations. Wind Chills will certainly drop 
below zero and we probably will eventually need to issue Cold 
Weather Advisories.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

Tonight...Medium Confidence (snow chances)

Light snow showers develop this evening, mainly after 00Z with 
the higher probabilities towards the south coast, Cape, and 
especially ACK. This will bring MVFR ceilings to the south 
coast/Cape and islands. Can't rule out brief localized IFR 
conditions with the greatest risk at ACK, where up to 2 inches 
of snow accumulation will be possible. There is a chance for 
scattered light snow showers/flurries for the other terminals 
with brief MVFR possible in any of the heavier snow showers. 

Showers diminish before midnight for most areas with the 
exception of Cape/islands. Light SW winds becoming NW.

Friday...High Confidence.

VFR. NW winds 5-10 knots, becoming SW Friday afternoon.

KBOS TAF...Medium confidence in TAF. 

There remains a low risk for light snow showers with some
accumulation, but flurries are more likely. The primary window
would be between 01-05Z.

KBDL TAF...High confidence in TAF. 

Outlook /Saturday through Tuesday/...

Saturday through Saturday Night: Mainly VFR, with local IFR
possible. Breezy. Chance SHRA.

Sunday: VFR. Breezy. Chance RA, chance SN.

Sunday Night: VFR. Breezy. Chance SN.

Martin Luther King Jr Day: VFR. Breezy. Slight chance SN.

&&

.MARINE...
Forecaster Confidence Levels:

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

High confidence.

Generally light winds (15 kt and less) and seas are expected 
through Friday night. 

Outlook /Saturday through Tuesday/...

Friday Night: Winds less than 25 kt. 

Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of seas approaching 5 ft. Chance of
rain showers. 

Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Rain showers
likely. 

Sunday: Winds less than 25 kt. Areas of rough seas. Chance of
rain. 

Sunday Night: Winds less than 25 kt. Rough seas up to 9 ft.
Chance of snow, rain. 

Martin Luther King Jr Day: Low risk for Small Craft Advisory
winds with gusts up to 25 kt. Rough seas up to 8 ft. Freezing
spray, slight chance of snow.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$

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