Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 251837
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
137 PM EST Sun Jan 25 2026

.WHAT HAS CHANGED...

- Higher confidence in 12-24 inch snowfall totals for the
  Berkshire and eastern Massachusetts. Higher confidence is
  driven by a more significant period of wraparound snow and
  snow showers Monday. Otherwise, a high impact storm continues
  to impact southern New England. 

&&

.KEY MESSAGES...

- Major winter storm underway this afternoon into much of the 
  day Monday. Heavy snowfall rates and most difficult travel 
  conditions continue this evening through 12-2am.

- Lingering moisutre leads to periods of light snow/snow showers 
  through much of the day Monday

&&

.DISCUSSION...
KEY MESSAGE 1...Major winter storm continues this evening and 
overnight. Difficult to impossible travel conditions persist through 
12-2am with 1-3" per hour snowfall rates. 

After a bit of an early start, snowfall rates have increased to 1 
inch per hour across much of the CWA this afternoon. These dangerous 
travel conditions continue well into the overnight as low pressure 
deepens offshore helping to increase mid level frontogenesis. The 
bulk of the snow falls through about 06z with gradual improvement 
into Monday morning as a dry slot works its way into the region. 
Storm totals are still holding steady as of the 18z update with 
totals expected to be in the 12"-18" range across the majority of 
southern New England, with 8"-12" expected on the Cape, Islands, and 
immediate southern coast. The higher elevations and northeastern MA 
will likely see 18"-24" for much of the 495 corridor including the 
Boston metro area.

Coastal low takes shape off the Del Marva Peninsula this afternoon 
helping to further increase mid-level frontogenesis. In response, a 
deep and robust layer of lift will extend through much of the column 
including the dendritic growth zone (DGZ). BUFKIT soundings even 
show the potential for 2 favorable layers for dendritic growth, one 
in the mid to upper levels, and another closer to the surface with 
the deep and substantial near surface cold pool. Attention turns 
from mid level frontogenesis to lower level frontogenesis (925-
850mb) as a steep low level temperature gradient associated with an 
incoming coastal front approaches from the south. Coastal front 
initially races north across the ocean then slows to a crawl this 
evening as it encounters the wedge of low level cold air on land. 
Warm front aloft still continues north overnight, so expecting +SN 
to slowly transition to heavy sleet along the south coast and move 
inland between 00-05z Furthest inland extent looks to be along west 
to east corridor extending from Providence RI to Plymouth MA. In 
these locations the mid level warm nose increases to +1-2C. Perhaps 
a bit more exciting for us weather lovers is the non-zero 
chance for +TSSN as the mid levels warm enough for some elevated
instability this evening into the overnight. Northeasterly LLJ 
increases to 30-40kts this evening as the low center passes just
S of Nantucket. Thus, could see a period of gusty winds and 
blowing snow especially over the southern waters, Cape and 
Islands. HREF blizzard probs remain around 20%-30%, between 22 
and 05z. The limiting factors for blizzard conditions along the 
south coast will be sleet and lower snow ratios as well as the 
short lived nature of the gustiest winds. 

Further inland, the  mid level warm front stops short of changing 
the precip type to sleet and instead brings a lower ratio snow that 
that will help to cap totals between 12 and 18 inches for much of 
the interior. Impressive temperature gradient develops overnight 
with surface temps rising to near 32 as far inland as PVD but 
staying in the lower teens at ORH on the other side of the surface 
warm front!

Prolific snow winds down from SW to NE as a mid level dry slot 
pushes into southern New England as 500-700mb RH values fall to 40-
60%. RH values like these are hostile to snow crystal growth and 
instead favor a period of "snizzle" or flurries. Any lingering snow 
eventually tapers to light flurries. Last hold out for light to 
moderate snow will be northeastern Massachusetts as northeasterly 
flow on Monday will allow for ocean-driven snow showers to persist 
into Monday afternoon. The next key message will better focus on 
Monday's snowfall. 

KEY MESSAGE 2...Periods of light to moderate snow continue behind 
low pressure as it pulls offshore Monday. 

Warm advection driven snow moves well N of the CWA but low pressure 
will still be in vicinity Monday morning. Most of the frontal lift 
is well away from the CWA between 12 and 16z Monday so expecting 
decent clean up weather for the first half of the day. Snow chances 
increase Monday afternoon as continued NE flow around elongated low 
pressure maintains ample low level moisture. Frontal boundary 
approaching from the west brings a wind shift to the W and so the 
low level convergence and frontogenesis allows for another period of 
light to even moderate snow through much of Monday afternoon. 
Additional snow accums from this feature will range from 1-4 inches, 
with areas W of the CT river closer to 1" and eastern MA closer to 
4". This additional snowfall gives us greater confidence in 12-24 
inch storm totals across the Berkshires where upslope will locally 
enhance totals as well as northeastern Massachusetts including 
Boston where the wraparound moisture lingers the longest. Lingering 
snow showers wind down after 00z Tues. 

Key Message 3...Abnormally cold and mostly dry with a low 
probability of another storm off the coast next weekend.

Overall benign weather is expected to follow this weekend's 
snowstorm. Dry, cold NW flow persists through at least the start of 
next weekend keeping precipitation out of the forecast for the most 
part while temperatures remain well below normal each day. Normal 
highs/lows for late January are in the mid 30s and low 20s 
respectively; we are forecasting highs in the teens and 20s with 
lows in the single digits thanks to an anomalously cold airmass 
overhead. A few shortwaves rounding the broader trough could bring 
some flurries off and on but on the whole things look dry. We'll 
continue to monitor a potential storm off the coast toward next 
weekend but odds are still favorable that it would pass harmlessly 
offshore.

&&

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

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

18z Update

Today and Tonight: High Confidence.

Heavy snow, widespread LIFR conditions through 08z. Snowfall rates 
of 1-3" per hour are likely. Snow lessens in intensity overnight 
into Monday but there should be a change to rain for a time on the 
Islands and possibly Cape Cod, with some sleet possible along the 
South Coast. Snow totals Monday morning range from 8-12" along the 
South Coast, Cape Cod, and Islands to 14-20" elsewhere, with 20-24" 
possible in the higher elevations and northeastern coast, including 
BOS. Much of this will fall from later Sunday afternoon through 
midnight Monday.

Monday: High Confidence in treads. Moderate Confidence in timing.

Snow begins to lighten up Monday morning. Prolonged northeasterly 
flow brings ocean enhanced snow to the northeastern coastal plain, 
including Boston, through midday. Winds shift to north westerlies 
Monday afternoon and flurries finally move offshore.

Monday Night: High Confidence.

MVFR, becoming VFR. Sky cover becoming clear. NW wind 10 knots with 
gusts 20 knots.  

KBOS Terminal...High Confidence in TAF. 

KBDL Terminal...High Confidence in TAF.

Outlook /Monday Night through Friday/...

Tuesday through Wednesday: VFR. Breezy. 

Wednesday Night: VFR. 

Thursday: VFR. Breezy. Slight chance SN.

Thursday Night through Friday: VFR. Breezy. 

&&

.MARINE...
Forecaster Confidence Levels...

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

Tonight through Monday Night: High confidence. 

Moderate to heavy snow through this evening as a coastal storm 
arrives and brings gale-foce wind from the northeast 20-35 knots 
through this afternoon and gusting 30-40 knots tonight. Somewhat 
warmer air noses north, changing to rain or sleet on most of south 
coastal waters overnight. Wind shifts northwest Monday afternoon 
with gusts less than 20 knots. With the shift in wind, snow showers 
are possible Monday afternoon, followed by drying conditions Monday 
night. 

Outlook /Monday Night through Friday/...

Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Rough seas up to 14 ft. 

Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Areas of rough seas. Slight chance of
snow. 

Wednesday: Winds less than 25 kt. Seas up to 5 ft. Chance of
freezing spray. 

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

Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Chance of snow, chance of freezing spray. 

Thursday Night: Strong winds with local gusts up to 30 kt.
Local rough seas. Chance of freezing spray, slight chance of
snow. 

Friday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. Chance of freezing spray, slight
chance of snow. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Storm Warning until 8 PM EST Monday for CTZ002>004.
MA...Winter Storm Warning until 8 PM EST Monday for MAZ002>024-026.
RI...Winter Storm Warning until 8 PM EST Monday for RIZ001>008.
MARINE...Gale Warning from 10 PM this evening to 5 AM EST Monday for 
     ANZ230.
     Gale Warning from 10 PM this evening to 6 AM EST Monday for 
     ANZ231.
     Gale Warning from 7 PM this evening to 1 AM EST Monday for 
     ANZ232>234.
     Gale Warning from 6 PM this evening to 1 AM EST Monday for 
     ANZ235-237.
     Gale Warning from 10 PM this evening to 1 AM EST Monday for 
     ANZ236.
     Gale Warning from 10 PM this evening to 7 AM EST Monday for 
     ANZ250-251.
     Gale Warning from 7 PM this evening to 7 AM EST Monday for 
     ANZ254.
     Gale Warning until 1 AM EST Monday for ANZ255-256.

&&

$$

DISCUSSION...Dooley/FT
AVIATION...Dooley
MARINE...Dooley