Lexington Weather

Lexington, Massachusetts, USA

13°F

1/23/2025 6:15am

Lexington Conditions: Clear
Temperature: 13.3°F / -10.4°C
Dew Point: 4.6°F
Relative Humidity: 68%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 30.34 in Steady
Visibility: 10 miles
Snow Today: 0.0 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 201704
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1204 PM EST Mon Jan 20 2025

.SYNOPSIS...
The last of the snow will be exiting the region by daybreak. 
Otherwise...an arctic airmass will bring frigid conditions with 
minimum wind chills on the order of 0 to 15 below zero at times 
through Wednesday morning. Temperatures moderate a bit Thursday and 
Friday, but they will remain below normal. Dry weather will 
generally prevail the rest of this week...but will need to watch a 
couple distant waves of low pressure in case they trend further 
northwest.

&&

.NEAR TERM /THROUGH TONIGHT/...
10AM Update

Remaining snow showers are tapering off the east coast of outer
Cape Cod at this hour. Abundant sunshine today with some breezy
northwest winds gusting above 20mph at times. Chilly day, but
somewhat seasonable with high temps ranging from the low 20s
across interior northwest MA to the mid-upper 20s across
southeastern MA and RI. There were no changes to the forecast
with this update as the previous forecast remains on track. 

Previous Discussion

Key Points...

* Last batch of showers will move across early this morning 
  with snow ending in the 4am-7am timeframe from west to east. 

* Below normal temperatures with a few pockets of flurries in
  afternoon. 

Radar early this morning displays one last batch of snow push 
across southern New England. This batch has a mix of light and
moderate snow. Radar QPE estimates rates in the more enhanced
band to be around .06/.07" which should translate to more
moderate snow rates. Surface stations have reported visibilities
around 3/4 mile during this band. This band should push across 
the eastern MA over the next few hours. Behind this band, there 
are lighter snow showers that move across the region. This still
puts us on track for snowfall ending between 4am-7am. For those
commuting this AM, the main concern will be slick and snow 
covered roads, especially if untreated. 

Cold will be the main story for the weather today. A well below
normal airmass advects into the region starting today. 850mb
temperatures fall to This will keep highs in the low to mid 20s
for most areas and upper 20s for the Cape and islands. As a 
side note, even colder air moves in by tomorrow, so be prepared
for that. As more enhanced pressure gradient this morning will 
keep elevated NW winds with periods of gusts up to 25 mph. This 
wind will also unfortunately make it feel even colder with wind 
chills in the single digits today. Please dress in layers and 
cover any exposed skin if planning to be outside today. As weak 
high pressure builds in this afternoon, winds weaken and turn 
westerly in most spots. Higher elevation spots may take a bit 
longer to decouple (this evening). Expect mainly dry conditions 
today; however, can't rule out a low chance (< 10%) for a pocket
or two of flurries/showers across the interior this afternoon 
with some residual moisture around.

&&

.SHORT TERM /TUESDAY THROUGH 6 AM TUESDAY/...
Key Points 

* Very cold with lows in the single digits and wind chills in
  negative single digits. 

The arctic airmass settles further over the region tonight.
850mb temperatures plummet to -20 to -22C overnight. The
combination of weakening winds, clear skies, and recent snowfall
ontop of the arctic airmass will support low temperatures in 
the single digits with some spots nearing zero. Even with a 
lighter wind, wind chills get into the negative single digits 
overnight for much of southern New England.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Key Messages...

* Bitterly Cold Wind Chills 0 to 15 Below Zero Tue AM/Wed AM
* Highs Tue & Wed mainly in the upper teens to the lower 20s
* Low Temps Tue night/Wed night single digits with some below zero
* Temps gradually moderate Thu/Fri...but still below normal
* Mainly dry this week...but watching distant system Thu night/Fri

Details...

Tuesday and Wednesday...

An arctic airmass will be entrenched in the area Tue and Wed. 850T 
near -21C/-22C on westerly flow will result in well below normal 
temps. Highs will be mainly in the upper teens to the lower 20s Tue 
and Wed. Low temps Tue night will generally be mainly in the single 
digits with some spots likely dropping below zero.

While this will be an arctic airmass...its delivery is from the west 
as opposed to the north northwest when we often get our most extreme 
cold temperatures. Nonetheless Wind Chills Tue AM and Wed AM will be 
between 0 and 15 below zero. We will be close to the criteria for 
Cold Weather Advisories...but because its right on the cusp we will 
defer that decision to the next shift.

We will need to watch a weak wave of low pressure passing well 
southeast of the Benchmark Tue night into Wed am. The vast majority 
of the region will remain dry. Worst case scenario would brief 
period of ocean enhanced light snow showers for mainly the Cape and 
Islands. Either way no real impact expected.

Thursday/Friday...

A ridge of high pressure shifts east of the region by Thu. This 
allows a southwest flow of slightly milder air to work into the 
region. Highs Thu/Fri will mainly be in the upper 20s to the lower 
30s...so still below normal albeit an improvement from what we will 
see the next few days. 

We also will need to keep an eye on a southern stream shortwave that 
is going to bring snow/ice right down to the Gulf Coast early this 
week. However...the upper level pattern does not appear to be 
amplified enough to bring the system close enough for much of an 
impact for us Thu night/Fri. However...there are a few individual 
ensemble members that have the storm close enough to us for a period 
of snow. Thinking this is a low probability at this point given the 
upper level pattern...but given it is a day 4/5 forecast we still 
will need to watch it.

Next Weekend...

It appears that a deep upper trough forming over the southwest U.S. 
will pump up height fields across the mid-Atlantic and especially 
the southeast. This should result in a more of a west southwest flow 
of air across the region next weekend. Highs probably well into the 
30s Sat and perhaps even some 40+ readings by Sun. Not looking at 
any significant storms at this time...but perhaps we see a few warm 
advection snow showers sometime Sun.

&&

.AVIATION /18Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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


18Z Update: 

Today...High Confidence.

Through 00Z...High Confidence.

VFR. Northwest winds around 10 knots. 20+ knot gusts begin to
diminish after 21-22Z.

Tonight...High Confidence

VFR. Winds becoming WSW around 5 knots or less.

Tomorrow...High Confidence

VFR. WSW winds around 10 knots. Increasing mid-level cloudiness
during the afternoon.

Tomorrow Night...High Confidence

VFR. Winds shift back to the northwest with speeds around 5
knots.

KBOS TAF...High Confidence in TAF. 

KBDL TAF...High Confidence in TAF.

Outlook /Tuesday through Friday/...

Monday through Wednesday: VFR. Breezy. 

Wednesday Night: VFR. 

Thursday: VFR. Breezy. 

Thursday Night: VFR. Slight chance SHSN.

Friday: VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

09z Update... 

High confidence...

Winds in the northern outer waters are expected to decrease
below Gale thresholds early this morning. Will let the Gale
Warning expire at 12z and re-issue as a SCA through 12z Tuesday.
 
Otherwise, expect SCAs generally through 12z Tuesday. Seas 4-9 
ft. 

Outlook /Tuesday through Friday/...

Monday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Rough seas up to 9 ft. Freezing spray. 

Monday Night: Winds less than 25 kt. Areas of rough seas.
Freezing spray. 

Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Freezing spray. 

Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Freezing spray, slight chance of snow showers. 

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

Wednesday Night: Winds less than 25 kt. 

Thursday: Winds less than 25 kt. Slight chance of snow showers.

Thursday Night: Winds less than 25 kt. Chance of snow showers. 

Friday: Winds less than 25 kt. Local rough seas. Slight chance
of snow showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 PM EST this evening for 
     ANZ230>234-236.
     Small Craft Advisory until 4 AM EST Tuesday for ANZ235-237.
     Small Craft Advisory until 10 PM EST this evening for ANZ250.
     Small Craft Advisory until 1 AM EST Tuesday for ANZ251.
     Small Craft Advisory until 3 PM EST Tuesday for ANZ254>256.

&&

$$

SYNOPSIS...Frank/Mensch
NEAR TERM...RM
SHORT TERM...Mensch
LONG TERM...Hrencecin
AVIATION...Hrencecin/RM
MARINE...Hrencecin/RM