Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 061951
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
251 PM EST Fri Feb 6 2026

.WHAT HAS CHANGED...
A winter storm watch has been issued for Essex county, beginning 4 
AM Saturday through 7 PM Saturday. Winter weather advisories have 
been issued for the same time period for the remainder of eastern MA 
into the Worcester Hills and down into RI.

&&

.KEY MESSAGES...

- Widespread 2-4 inches of snow likely later tonight through Sat, 
  with localized bands of heavier snow across northeast MA, possibly 
  up to 8 inches in Essex county, including Cape Ann. Less snow 
  westward into CT and western MA. Ocean effect snow showers over 
  Cape Cod Sat night.

- Dangerous cold Saturday night into Sunday, gusty winds will
  lend to wind chills 10-30 degrees below zero. In addition,
  freezing spray becomes hazardous for the mariners. 

&&

.DISCUSSION...
KEY MESSAGE 1...Widespread 2-4 inches of snow later tonight through 
Sat, but localized bands of heavier snow over northeast MA, possibly 
yielding amounts up to 8 inches. Ocean effect snow showers over Cape 
Cod Sat night.

-AO and -NAO teleconnections yielding a very suppressed polar jet 
this period, with storm track well south of New England. However, 
this supports a potent, high latitude closed low to descend from 
James Bay into New England this weekend. This feature will be 
accompanied by an arctic front Sat, which will yield a complex snow 
event for SNE. This vigorous closed low induces cyclogenesis well 
southeast of the 40N/70W benchmark Sat. However, such strong forcing 
for ascent results in an inverted/Norlun trough from the offshore 
low extending northwest into SNE Sat. This will result in narrow 
bands of snow Sat moving west to east across CT/MA/RI.

Model data reveals a combination of steep low level lapse rates (up 
to 9C/km in 0-2 km layer), deep saturated layer, strong convergence 
and at least modest omega in the snow growth region, will yield a 2-
4 hr period of moderate to perhaps heavy snow at times, from late 
Sat morning into the afternoon. The snow squall parameter ramps up 
rapidly between 18-22z across eastern MA Sat afternoon. 12z NAM 
bufkit for KBVY, indicates up to 20 u/bars of lift in the -10C to -
15C layer 15z-18z. This should yield favorable SLR and low vsbys. 
This is also supported by HREF offering 30-50% probs of hourly 
snowfall rates exceeding 1" and 20-30% for greater than 2" per hour, 
with these high rates focused across eastern MA westward into RI and 
the Worcester Hills. Duration of strong lift, deep saturation and 
steep low level lapse rates is brief (2-4 hr window) and this will 
limit accumulations to mainly 2 to 4 inches, with highest amounts 
across RI and central-eastern MA.

This boundary becomes more enhanced as it enters eastern MA, with 
multiple models generating over 0.50 inches of qpf across Essex 
county, with some ocean effect enhancement contributing to the 
higher totals. In addition, the 13z NBM (v5.0) snow probs have 20-
30% probs of 8+ inches across Essex county, esp the Cape Ann area, 
and 50% prob of 6+ inches of snow. Given multiple models have strong 
low level convergence, steep low level lapse rates, a deep saturated 
layer and at least modest forcing for ascent in the snow growth 
region, will hoist a small winter storm watch area for Essex county. 
Snowfall projections here will be for 4-8", with even a low prob of 
isolated higher amounts pending the evolution of this mesoscale snow 
band associated with the inverted/Norlun trough. Keep in mind, these 
mesoscale snow bands are very difficult to forecast and this is a 
situation where snowfall amounts can vary greatly over short 
distance. Thus, continue to check back and monitor our updated 
forecast. For the remainder of coastal eastern MA, given the OES 
component, isolated amounts of up to 6 inches is possible. 

For the remainder of the region, the short duration/progressive 
nature of the snow bands, thinking most locations across the 
remainder of eastern and central MA into RI will experience 2-4". 
Thus, have issued a winter weather advisory for this area. Given the 
boundary is not as robust as it enters western MA into CT, thinking 
less snowfall here, 1-3". Hence, did not issue an advisory for this 
region. Not a blockbuster snow event, but roads will become snow 
covered and travel will become difficult, especially in
northeast MA from late morning into the afternoon.

The snow should taper off in the early afternoon in CT/western MA 
behind the arctic front, then exiting offshore 4-7 PM across eastern 
MA. 


KEY MESSAGE 2...Dangerous cold Saturday night into Sunday, gusty 
winds will lend to wind chills 10-30 degrees below zero. In addition, 
freezing spray becomes hazardous for the mariners. 

Forecast confidence is high for dangerous cold conditions Saturday 
night through Sunday, in addition, high confidence in heavy freezing 
spray across most waters, with the exception of Boston Harbor. This 
is all brought by an Arctic front, arriving late Saturday afternoon 
as 925mb temperatures fall from 7-10 below zero to 20-25 below zero 
cross the interior and 10-15 below zero across the coastal plain. In 
conjunction is a 925mb LLJ with winds 35-45 knots, with is roughly 
the height of the mixed layer. Strong northwest winds 30-40 mph will 
make the air temperature, which will be 5-10 below zero across the 
interior and 0-5 above zero across the coastal plain. Warmest areas 
are the outer Cape and Nantucket where lows are in the low teens. 

There hasn't been changes to the headlines. The Extreme Cold Warning 
and Cold Weather Advisory go in effect Saturday evening into Sunday 
afternoon. The only area in southern New England not included is 
Nantucket. Areas under the Extreme Cold Warning should prepare for 
wind chill values as low as 20-30 degrees below zero. As for areas 
under the Cold Weather Advisory, wind chill values are expected to 
be as low as 15-20 degrees below zero. There isn't much improvement 
Sunday afternoon, while the 925mb jet diminishes, surface winds 
remain gusty 20-30 mph. Leading to wind chill values Sunday 
afternoon in the single digits on either side of zero. 

During this time, it's worth reminding boater of heavy freezing 
spray across all the waters as icing rates could reach 0.5-1.0 inch 
per hour. This has prompted a Heavy Freezing Spray Warning for all 
waters with exception of Boston Harbor, where a Freezing Spray 
Advisory has been issued. 

A 1035mb high builds in Sunday night into Monday across the eastern 
Great Lakes, leading to diminishing winds. Still very cold, it's a 
possibility there may be a need for Cold Weather Advisory headlines 
again Sunday night into Monday morning. Opt'd to hold off on any 
issuances at this time as not to cause confusion with the more 
dangerous of the cold. Nevertheless, air temperatures are only a 
degree or three higher Sunday night into Monday morning, but with 
less wind, the wind chill values are expected to be 5-15 degrees 
below zero with far interior Massachusetts as low as 20-25 degrees 
below zero. 

The area of high pressure remains Monday and Tuesday, below normal 
temperatures continue into early next week, daytime highs are in the 
teens and 20s on Monday, near 30 on Tuesday, and trending towards 
the middle 30s for Wednesday and Thursday. Outside of a weak clipper 
system on Tuesday there is fairly quiet conditions early next week. 
Will need to monitor a mid to late week system, though there is low 
confidence in this part of the forecast due model disagreement on 
placement and timing. Stay tuned. 

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

18z TAF Update...

Tonight into Saturday...Moderate confidence.

Conditions lowering to MVFR-IFR as areas of snow develop from 
late evening through Sat. Localized heavier snow bands possible 
with LIFR conditions, especially Sat in eastern MA. Gusts 20-25 
knots develop by mid-morning, increasing to up to 30 knots by 
the afternoon.

Saturday night...Moderate confidence.

MVFR becoming VFR as the night goes on and snow starts to clear
the region. Some snow showers may linger longer towards the 
Cape.

Outlook /Saturday Night through Wednesday/...

Sunday: VFR. Windy with gusts up to 35 kt. 

Sunday Night: VFR. Windy with local gusts up to 30 kt. 

Monday through Monday Night: VFR. Breezy. 

Tuesday through Tuesday Night: VFR. 

Wednesday: Mainly VFR, with local IFR possible. Chance SN.

&&

.MARINE...
Forecaster Confidence Levels...

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

2 PM update...

Headlines: 

* Gale Warnings from Sat afternoon into Sunday.

* Heavy Freezing Spray warnings for Saturday afternoon through 
  early Mon morning.

Light NE winds through tonight, then increasing NE winds Sat morning 
turning N-NW later Sat into Sun with gusts increasing to 35-40 kt 
behind the arctic front. Areas of heavy freezing spray will develop, 
especially Sat night as gusty winds combine with arctic air moving 
into the region. Heavy freezing spray produces ice accretion rates 
up to 1 inch/hr creating very dangerous conditions for vessels.

Outlook /Saturday Night through Wednesday/...

Sunday: Strong winds with gusts up to 35 kt. Rough seas up to
12 ft. Freezing spray, slight chance of snow. 

Sunday Night: Strong winds with gusts up to 30 kt. Rough seas
up to 9 ft. Freezing spray. 

Monday through Monday Night: Winds less than 25 kt. Seas up to
5 ft. Freezing spray. 

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

Tuesday Night: Winds less than 25 kt. 

Wednesday: Winds less than 25 kt. Slight chance of rain, slight
chance of snow.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Extreme Cold Warning from 6 PM Saturday to 1 PM EST Sunday for 
     CTZ002>004.
MA...Extreme Cold Warning from 6 PM Saturday to 1 PM EST Sunday for 
     MAZ002>004-008>012.
     Winter Weather Advisory from 4 AM to 7 PM EST Saturday for 
     MAZ004-005-012>021-026.
     Cold Weather Advisory from 6 PM Saturday to 1 PM EST Sunday 
     for MAZ005>007-013>023-026.
     Winter Storm Watch from late tonight through Saturday evening 
     for MAZ006-007.
     Winter Weather Advisory from 4 AM Saturday to 1 AM EST Sunday 
     for MAZ022>024.
RI...Winter Weather Advisory from 4 AM to 7 PM EST Saturday for 
     RIZ001>008.
     Cold Weather Advisory from 6 PM Saturday to 1 PM EST Sunday 
     for RIZ001>008.
MARINE...Gale Warning from 4 PM Saturday to 7 AM EST Sunday for ANZ230-
     236.
     Freezing Spray Advisory from 4 PM Saturday to 7 PM EST Sunday 
     for ANZ230.
     Gale Warning from 4 PM Saturday to 1 PM EST Sunday for ANZ231-
     232-250-251-254.
     Heavy Freezing Spray Warning from 4 PM Saturday to 7 AM EST 
     Monday for ANZ231>237-250-251-254>256.
     Gale Warning from 1 PM Saturday to 10 AM EST Sunday for 
     ANZ233>235-237.
     Gale Warning from 1 PM Saturday to 1 PM EST Sunday for ANZ255-
     256.

&&

$$

DISCUSSION...Dooley/Nocera
AVIATION...McMinn/Nocera
MARINE...Dooley/Nocera