Old Res Weather

Lexington, Massachusetts, USA

35°F

2/16/2025 7:17pm

Lexington Conditions: Light snow, 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: 1½ miles
Rain Today: 0.01 in
UV Index: $VPuv None

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 200526
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1226 AM EST Tue Jan 20 2026

.WHAT HAS CHANGED...
Confidence continues to increase for a prolonged Arctic outbreak 
beginning at the end of this week into this weekend.  Confidence 
remains low in the late weekend coastal storm.

&&

.KEY MESSAGES...

- Cold and dry tonight through Tuesday night. Wind chill index
  near or below zero tonight through Wednesday

- Near-normal to mild temperatures midweek. A weak clipper
  system brings low chances of higher terrain snow showers and
  light rain for the coastal plain. 

- Increasing confidence in an Arctic outbreak beginning Friday
  night with dangerous cold and wind chills, while low
  confidence remains in a late- weekend coastal storm.

&&

.DISCUSSION...
KEY MESSAGE 1...Cold and dry tonight through Tuesday night. 
Wind chill index near or below zero tonight through Wednesday


A cold front will bring an arctic air mass to the region tonight and 
last through Tuesday night. Strong CAA will bring 850mb temps down 
to -20C by Tuesday morning, resulting in an extended period of sub-
freezing temperatures starting at sunset tonight. Any melted snow 
from today will quickly refreeze tonight, and untreated surfaces 
could become slippery. Temperatures take a dive off the deep end 
tonight, dropping into the single digits to low teens across the 
region.  With winds picking up to 20-30mph from CAA, the wind chill 
index/feels-like temperatures will drop to near or slightly below 
zero across the region.  CAA continues into tomorrow, and 
temperatures only warm into the mid-teens in the west and mid-20s in 
the east.  Gusty winds also continue into Tuesday with gusts of 15-
25mph. Wind chill index will make it feel like the single digits to 
low teens outside.  Winds drop off Tuesday night as high pressure 
builds in just to the south.  With clear skies, light winds, and 
fresh snowpack, overnight temperatures will drop into the single 
digits across the region, with low teens near the coasts. 


KEY MESSAGE 2...Near-normal to mild temperatures midweek. A weak 
clipper system brings low chances of higher terrain snow showers and 
light rain for the coastal plain. 


After a brief shot of Arctic air temperatures moderate for Wednesday 
and Thursday, this period features a chance of precipitation mainly 
between Wednesday evening and Thursday. Driving the weather midweek are 
a mid-level low over Hudson Bay with embedded shortwave energy rotating 
around the cyclonic flow. This supports development of a weak Alberta 
clipper tracking southeast from the Canadian Rockies towards the 
northeast. Ahead of it, a developing southerly LLJ with wind speeds 30 
to 50 knots, which advects a somewhat warmer air mass into southern New 
England. Near-normal temperatures Wednesday and an increasing S-SSW 
wind. Warm advection rain and/or higher terrain snow showers are 
possible, 20-35 POP, from late Wednesday through the first-half of 
Thursday. As typical with most clippers, moisture content is limited, 
as PWATs are between 0.2" and 0.4". With little downstream blocking, 
the system is progressive. Ensembles guidance remains unimpressive, 
with probabilities for snowfall exceeding one inch generally less than 
20% range in interior southern New England. The LLJ weakens Thursday, 
still fairly mild for mid-January as highs return to the upper 30s and 
low 40s. 

KEY MESSAGE 3...Increasing confidence in an Arctic outbreak beginning 
Friday night with dangerous cold and wind chills, while low confidence 
remains in a late-weekend coastal storm. 

While still several days away, confidence continues to increase in a 
significant Arctic outbreak impacting southern New England beginning 
late Friday night and persisting through next weekend. As noted in 
prior discussions, a lobe of the Polar Vortex is forecast to break off 
and drive much colder air into the region. This cold air mass does not 
appear to be short-lived, with the Climate Prediction Center (CPC) 
highlighting much of the Northeast, Upper Midwest, and Great Lakes 
under a moderate risk for much below normal temperatures into the 
middle of next week. For the upcoming weekend, overnight low 
temperatures and wind chills may fall to around -20F in the higher 
terrain and -10F across the coastal plain. Raising the potential for 
Cold Weather Advisories. The Magnitude of this cold is notable, with 
the forecast 925mb temperatures on the order of -25C to -30C, more 
typical of 500mb. Those with outdoor plans this weekend should continue 
to monitor the forecast closely. Given these conditions, mariners 
should be prepared for a high likelihood of freezing spray, though the 
extent and severity remain uncertain at this time. 

In addition, there are indications of a potential coastal system late 
next weekend. While some guidance suggest a system may pass offshore 
Sunday into Sunday night, confidence remains low. Recent AI-based 
guidance favors greater impacts across southern New England; however, 
QPF may be overstated and may not adequately resolve a sharp northern 
gradient. For now, maintained low-end PoPs, reflecting only a slight 
chance for snow showers.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

Today: High Confidence.

VFR. West winds gusting 20-25 knots, becoming light after
sunset.

Tonight: High Confidence.

VFR. West winds 5-10 knots.

Wednesday: High Confidence.

VFR. Southwest winds 5-10 knots.
 
KBOS Terminal...

VFR. Gusty W winds 23-27 knots through this evening.

KBDL Terminal...

VFR. Increasing W winds through this evening with gusts of 
20-25 knots.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Mainly VFR, with local MVFR possible. Breezy.
Slight chance RA, slight chance SN.

Thursday through Friday Night: VFR. Breezy. 

Saturday: VFR. Breezy. Slight chance SN.

&&

.MARINE...
Forecaster Confidence Levels...

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

Rest of Today through Tuesday Night...

Cold front will bring a period of strong westerly winds to the
waters tonight through Tuesday afternoon with gusts of 30-35
knots. Seas increase tonight highest in the southern waters at
10-13 feet, and 7-10 feet in the northern waters. Winds decrease
quickly Tuesday night, with gusts dropping below 20 knots. Seas
also gradually diminish to 4-6 feet. With cold arctic air 
moving offshore, expecting light freezing spray both tonight and
Tuesday night as air temps drop into the 20s.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Strong winds with gusts up to 30 kt. Areas of
rough seas. Slight chance of rain. 

Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Slight chance of rain. 

Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. 

Friday: Moderate risk for Small Craft Advisory winds with local
gusts up to 30 kt. Seas up to 5 ft. 

Friday Night: Strong winds with gusts up to 35 kt. Areas of
rough seas. Freezing spray likely, slight chance of snow. 

Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas. Freezing spray likely,
slight chance of snow. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ230-
     236.
     Gale Warning until 9 AM EST this morning for ANZ231>235-237-
     250-251-254>256.

&&

$$

DISCUSSION...BW/McMinn
AVIATION...McMinn
MARINE...McMinn