Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 091924
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
224 PM EST Fri Jan 9 2026

.WHAT HAS CHANGED...

Increased confidence in a period of icing Saturday night into 
Sunday morning across the highest terrain of northern 
Massachusetts. Confidence increasing in a period of northwest 
wind gusts of 35 to 50 mph Sunday night especially during the 
overnight hours along with a brief shot of colder weather. Gale 
Watches also issued for all waters Sunday night into Monday 
morning. Milder temperatures return Tuesday and Wednesday before
a pattern change to colder and perhaps some unsettled weather 
arrives by late next week.
 
&&

.KEY MESSAGES...

- Period of showers and light rain tonight.

- Soaking rain arrives later Saturday into early Sunday. Rain 
  for most areas with an increasing chance for icing across the 
  highest terrain in Northern Massachusetts. 

- Becoming windy & turning colder Sun night into Mon with a period 
  of NW wind gusts of 35 to 50 mph possible later Sun night. 
  Low risk for a brief snow squall too.

- Milder temperatures quickly return Tue and especially by Wed when 
  highs may approach 50 in some locations.

- Turning colder Thu into Fri and will have to watch an offshore 
  storm for the potential of mixed precipitation/snow if it tracks 
  close enough to the coast. 


&&

.DISCUSSION...

KEY MESSAGE 1...Period of showers and light rain tonight. 

Weak frontal boundary passes through southern New England tonight 
with a broken band of showers and steady rain. Still not expecting 
much in terms of totals or intensity although rain may extend into 
early Saturday morning across the Cape and Islands. As mentioned 
previously, the best forcing is displaced well north, across 
northern New England and southern Quebec. Still, a few light rain 
showers arrive across western Massachusetts and Connecticut between 
5 PM and 7 PM, then central and eastern Massachusetts and Rhode 
Island between 7 PM and 9 PM. Despite higher than normal PWATs, do 
not expect much QPF, once again due to lack of forcing. Rain totals 
range between 0.1" and 0.2". Showers exit off the coast between 12 
AM and 3 AM Saturday as the trailing cold front pushes through the 
region. Not as cold, lows are in the middle to upper-30s. Though, 
the Berkshires likely drop to the low-30s, here there would be a 
threat of black ice overnight. 

KEY MESSAGE 2...Soaking rain arrives later Saturday into early Sunday. 
Rain for most areas with an increasing chance for icing across the 
highest terrain in Northern Massachusetts. 

More significant system moves towards the region later Saturday. 
Parent low over the Great Lakes moves NE as a secondary low develops 
just S of New England. Notable feature with this system will be an 
enhanced SW jet will help transport above normal moisture into 
southern New England, around 230-280 percent of normal. This will 
set the stage for a soaking rain for southern New England. Rain will 
likely arrive in the afternoon spreading from south to north, 
tapering off early Sunday morning. Showers may linger across the 
south coast and Cape/Islands through the afternoon. There is still a 
decent range in QPF likely owing to track of the surface low. There 
continues to be a fairly wide range in the 25th-75th percentiles 
among ensemble guidance. For northern MA amounts range from 0.20- 
0.50" and 0.40-1.0" for the south coast and Cape/Islands. 

High-res guidance continues to highlight the chance for icing and/or 
mixed precipitation across elevated portions of northern 
Massachusetts Saturday night into Sunday. The trend in the 12z 
guidance suite has been to develop a secondary surface low just 
offshore. Northerly flow around this feature would help to keep a 
wedge of colder air over the interior through Saturday night. Warm 
nose aloft means a chance of freezing rain over a snow event. HREF 
Freezing Rain Accumulation Model (FRAM) has ticked up accumulations 
across the higher terrain of western Franklin and Hampshire counties 
with the 12z run indicating the chance of 0.05-0.10" amounts. 
Continued with the previous shift's thinking and blended in a 
portion of cooler guidance to account for the potential for the 
colder, around freezing temperatures. Still looking like a marginal 
thermal profile so holding off on a winter weather advisory for
now.

KEY MESSAGE 3...Becoming windy & turning colder Sun night into Mon 
with a period of NW wind gusts of 35 to 50 mph possible later Sun 
night. Low risk for a brief snow squall too.

Rapidly intensifying low pressure will be lifting into the Canadian 
Maritimes Sun night. This will allow for a brief shot of windy and 
cold weather to work into the region. Strong CAA along with Bufkit 
support a period of northwest wind gusts of 35 to 50 mph later Sun 
night. It is possible we may briefly reach Wind Advisory criteria in 
some locations. In addition...there will be a low risk for a 
localized snow squall too. Impressive shortwave energy along with 
modest 1000 to 700 mb lapse rates...but low level moisture may be 
limited. So right now calling it a low probability...but something 
to watch.

Otherwise, main story is dry but windy and colder weather. Low temps 
by daybreak Monday will be in the 20s with highs only recovering 
into the 30s during the afternoon. Wind chills probably range from 
the high single digits to the middle teens by daybreak Mon. 

KEY MESSAGE 4...Milder temperatures quickly return Tue and especially 
by Wed when highs may approach 50 in some locations.

The upper trough is fairly progressive and surface high pressure 
will quickly be moving east and away from the mid-Altantic states. 
This will result in the quick return southwest of milder air back to 
the region. Highs on Tue should be back into the 40s and by Wed some 
locations may even reach 50. Dry weather probably dominates...but 
shortwave energy may result in a few showers late Tue night/Wed 
morning.

KEY MESSAGE 5...Turning colder Thu into Fri and will have to watch 
an offshore storm for the potential of mixed precipitation/snow if 
it tracks close enough to the coast. 

Long range guidance is in agreement in the likelihood of a pattern 
change back to colder weather by late next week. How quickly this 
happens and the magnitude of this remains uncertain...but appears 
that a -EPO will be developing. This will result in ridging over the 
Pacific and a northeast trough developing...so temperatures will be 
turning colder Thu and Fri. We will also need to watch the 
development of an offshore low pressure system Thu into Fri. If it 
comes close enough to the coast...the potential would exists for 
mixed precipitation and/or snow. A lot of the guidance currently 
favoring a glancing blow/miss...but there is a large spread in the 
individual ensembles and it would not take too much of a shift 
northwest to change things significantly. It is way too early to say 
much more and probably will be at least a few days until we have a 
better idea. 

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...

Forecaster Confidence Levels...

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

TAF Update: 18z

Tonight... Moderate Confidence. 

Areas of SHRA move in from west to east 22z-00z, conditions 
briefly lower to IFR, showers diminish between 03-06z, improving
back to VFR 06-09z, while MVFR lingers on the Cape and Islands 
through 09z-12z. Wind shifts to the west to west- northwest 
between 04z-10z, winds speeds are 5 to 10 knots, slightly higher
for coastal terminals.

Saturday... Moderate Confidence. 

VFR to start, then lowering to MVFR from south to north, along with 
showery rain, mainly after 18z/21z. Light north wind becomes east at 
5 to 10 knots. 

KBOS Terminal... Moderate Confidence. 

Moderate confidence in MVFR developing thru the evening. 

KBDL Terminal... Moderate Confidence.

MVFR to IFR ceilings developing this evening into the overnight.

Outlook /Sunday Night through Wednesday/...

Sunday Night: VFR. Strong winds with gusts up to 45 kt. Slight
chance SHSN.

Monday: VFR. Strong winds with areas of gusts up to 45 kt. 

Monday Night through Tuesday: VFR. Breezy. 

Tuesday Night through Wednesday: VFR. Breezy. Slight chance
SHRA.

&&

.MARINE...

Forecaster Confidence Levels...

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

Today through Sunday.. High Confidence. 

Elevated seas continue tonight 4 to 6 feet, localized areas of 7 
feet on the outermost southern waters. Showery rain overnight, not 
expected to be at all impactful. Saturday morning winds go light and 
flip to the east as a quasi-stationary front lifts from the south to 
the north, rain accompanies this front as well during the early to 
mid-afternoon. Increasing winds later Sunday as CAA increases behind 
a cold front. Gale conditions will be possible by Sunday night.

Outlook /Sunday Night through Wednesday/...

Sunday Night: Moderate risk for gale force winds with gusts up
to 45 kt. Rough seas up to 13 ft. Slight chance of rain
showers, slight chance of snow showers. 

Monday: Low risk for gale force winds with gusts up to 35 kt.
Areas of rough seas. 

Monday Night through Tuesday: Moderate risk for Small Craft
Advisory winds with gusts up to 25 kt. Local rough seas. 

Tuesday Night: Strong winds with areas of gusts up to 30 kt.
Areas of seas approaching 5 ft. Slight chance of rain showers. 

Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Local rough seas. Slight chance of rain
showers. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Gale Watch from Sunday evening through Monday morning for 
     ANZ230>237-251.
     Small Craft Advisory from 7 PM this evening to 3 AM EST 
     Saturday for ANZ235-237.
     Small Craft Advisory from 7 PM this evening to 7 AM EST 
     Saturday for ANZ250-254>256.
     Gale Watch from Sunday evening through Monday afternoon for 
     ANZ250-254>256.

&&

$$

DISCUSSION...FT/Frank
AVIATION...FT/Frank
MARINE...FT/Frank