Old Res Weather

Lexington, Massachusetts, USA

32°F

12/13/2024 10:42am

Lexington Conditions: Clear
Temperature: 31.6°F / -0.2°C
Dew Point: 14.2°F
Relative Humidity: 48%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 30.58 in Steady
Visibility: 10 miles
Rain Today: 0.00 in
UV Index: $VPuv None

Area Forecast Discussion
for Lexington, MA

        
000
FXUS61 KBOX 131504
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1004 AM EST Fri Dec 13 2024

.SYNOPSIS...
Strong high pressure building in from the west will result in dry 
but cold weather with below normal temperatures through the weekend. 
Shift to a more unsettled weather pattern Monday into next week with 
periods of precipitation possible. Temperatures trend above normal 
through mid-week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1000 AM Update: 

Forecast holding up pretty well with a rather cold and dry day
ahead. No significant change needed attm. 

Previous discussion:

* Plenty of sunshine but cold today
* High temps mainly in the lower-middle 30s

Large high pressure will slide eastward today across the Great
Lakes. Other than a batch of mid level cloudiness moving across
the region into mid-morning...plenty of sunshine is on tap for
today. However...the low December sun angle coupled with 925T 
near -10C will result in a cold day. High temps will range from
the upper 20s in the high terrain...to mainly the lower to
middle 30s elsewhere. These temperatures are about 10 degrees
below normal for this time of year. WNW winds will gust between
15 and 25 mph later this morning and afternoon making it feel
even colder.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Key Messages...

* Mostly clear & cold tonight with lows mainly in the teens
* Sunny & cold Sat with highs mainly between 30 and 35

Details...

Tonight...

The very strong high pressure system near 1050 mb noses into the
region from the west. This will result in mainly clear
skies...calm/light winds and an ideal night of radiational
cooling. This should allow low temps to bottom out between 10
and 15 degrees in the normally coldest outlying locations...to
the lower 20s in the Urban Heat Island of Boston.

Saturday...

The 1050 mb high pressure system will be in control of our
weather Sat. This will provide plenty of sunshine but with
continued cold temperatures. Highs will generally be between 30
and 35...but the winds will be lighter than today given the high
pressure system in control.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Key Messages: 

* More unsettled weather Sun through next week with periods of 
  precipitation possible. 

* Below normal temperatures Sunday, trending above normal early next 
  week. 

High pressure remains in place Saturday night resulting in another 
night of clear skies, radiational cooling and thus chilly 
temperatures. Temperatures likely drop into the mid to upper teens 
across most areas with some low 20s for some of the coastal 
locations. The higher terrain spots across the interior may see lows 
drop into the lower teens and perhaps some single digit values. 

Ensemble guidance continues to show a consensus on a shift to a more 
unsettled/active pattern Sunday into next week. There is a general 
signal for increased moisture phased with the passage of a few 
shortwave troughs in the flow aloft. This will give way to periods 
precipitation. There are still some differences among individual 
model/solutions with respect to details (ie timing). Precipitation 
chances increase Sunday night into Monday morning with the first 
leading weak wave. With shallow cold air in place at the surface to 
start and warm air advection slowly moving in from the south, there 
is potential for light mixed precip/icing for parts of the interior 
at the onset of precipitation. Can't rule out snow for the interior 
if precip moves in early Mon morning. With timing still uncertain, 
this is something we'll have to watch with potential for minor 
impacts to the Mon AM commute. Winds transition southerly as warm 
air advects into the region toward the afternoon. This should favor 
rain for the afternoon as highs rise toward the low 40s. 

There is a better signal for moisture into Tuesday as the main 
shortwave trough/front moves across which may result in a period of 
higher coverage light rainfall. Temperatures will be sufficiently 
above normal with highs into the 50s. Conditions dry out into 
Wednesday with W/WSW flow aloft with temperatures stay near to 
slightly above normal. Ensemble guidance is hinting at potential for 
another late week system; however, details are uncertain at this 
time. There is also a general signal for cooler air to return to the 
region for the weekend.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

15z TAF Update:

Through Tonight: High confidence.

VFR. West/northwest wind 8 to 13 knots with some 20+ knot gusts
by afternoon. Winds decrease after 21z becoming calm/light from
the NW tonight.

Saturday...High Confidence 

VFR with a low risk of some marginal MVFR ceilings east of KHYA
from ocean effect clouds. NW winds less than 10 knots.

KBOS TAF...High Confidence in TAF. 

KBDL TAF...High Confidence in TAF. 

Outlook /Saturday Night through Tuesday/...

Saturday Night through Sunday Night: VFR. 

Monday: Mainly VFR, with local IFR possible. Chance RA, chance
SN.

Monday Night: MVFR/IFR conditions possible. Breezy. Chance RA.

Tuesday: Mainly MVFR, with local IFR possible. Breezy. RA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Saturday...High Confidence.

A very strong high pressure system across the Great Lakes will
build eastward tonight into Saturday. Cold advection over the 
relatively mild ocean will result WNW wind gusts of 20-25 knots.
We opted to continue the small craft headlines for the outer- 
waters...where we also have some lingering 5+ swell. Any 
lingering small craft conditions should come to an end during 
the evening as this high pressure system builds east. No marine 
headlines will be needed on Sat with high pressure in control.

Outlook /Saturday Night through Tuesday/...

Saturday Night through Sunday Night: Winds less than 25 kt. 

Monday: Winds less than 25 kt. Chance of rain. 

Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain. 

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Rain.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ250-
     254>256.

&&

$$

SYNOPSIS...Frank/Mensch
NEAR TERM...Frank/Loconto
SHORT TERM...Frank
LONG TERM...Mensch
AVIATION...Frank/Loconto/Mensch
MARINE...Frank/Loconto/Mensch