Lexington Weather

Lexington, Massachusetts, USA

54°F

5/11/2024 12:36pm

Lexington Conditions: Mostly cloudy
Temperature: 53.8°F / 12.1°C
Dew Point: 44.6°F
Relative Humidity: 71%
Wind: Calm, 10-min avg: Calm, gust: 6 mph
Barometer: 29.82 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 041931
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
331 PM EDT Sat May 4 2024

.SYNOPSIS...

Cloudy and cool weather is on tap through Sunday with a period of 
widespread showers arriving from the west...mainly later Sunday into 
Sunday night. Mild and dry to start the work week before cooler and 
unsettled conditions Wednesday through next weekend

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...

330 PM Update...

* Clouds continue to overspread the region off the ocean tonight
* Overnight low temps mainly in the 40s

The upper level ridge axis will be shifting east of the region. This 
coupled with high pressure in the vicinity of the Canadian Maritimes 
will result onshore flow. As the boundary layer cools...expect low 
clouds to continue to develop and expand westward tonight. Dry 
weather will prevail tonight...but we may see a few spot showers 
develop near daybreak west of the CT River Valley. Overnight low 
temps will bottom out mainly in the 40s.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...

Key Points...

* Cloudy/cool Sun with showers arriving across the interior
* A period of widespread showers Sun night across the entire region

Details...

Sunday and Sunday night...

High pressure will shift east of the Canadian Maritimes as shortwave 
energy approaches from the west on Sunday. Onshore flow low level 
flow will result in cloudy skies persisting and cool temperatures 
too. Highs will only be in the 50s even across the distant interior. 

While a few warm advection spot showers are possible across the 
interior during the morning...the stronger forcing/deeper moisture 
does not arrive until the afternoon. So thinking the main threat for 
showers will be be Sunday afternoon across interior MA & CT...but 
should wait until late Sunday afternoon/evening across the coastal 
plain. Enough forcing exists for a period of widespread showers 
Sunday night. Modest forcing and Pwats 1-2 standard deviations above 
normal could result in a brief downpour or two. While we can not 
rule out a rumble or two of thunder with some marginal elevated 
instability...thinking it was not worth inserting into the forecast 
at this point. Low temperatures Sunday night will mainly be in the 
middle to upper 40s. 

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...

* Generally dry with above normal temperatures Monday and Tuesday

* Persistent period of cool temps and heightened rain chances 
  Wednesday through early next week. 

Tale of two patterns for the upcoming work week with strong 
upper level ridging in place through Tuesday before a trough 
develops for the second half of the week. 

Some residual showers may linger into Monday morning, primarily 
across far southeastern MA and the Cape. Weak frontal passage may 
initiate some shower activity come Monday evening but with drying 
flow aloft, questions remain on the geographic spread of this second 
round of showers. All in all, Monday looks to shape up as a 
primarily dry day, with above normal temperatures as boundary layer 
temperatures warm to around 15C. As noted by the previous 
forecaster, ensemble probabilities of 70F+ temps remain high, 
between 80-100%, across the interior. Tuesday continues to look like 
the pick of the week as temperatures soar well into the 70s. 
Downsloping northwest flow that develops after the lunch hour and 
abundant sunshine should allow for a few localities in the CT River 
Valley to make a run at 80F. While ensemble probabilities remain low 
regarding temps hitting the 80F mark, conditions appear to be a 
recipe for an overachieving type day. For both Monday and Tuesday, 
weak pressure gradient will allow for seabreeze development, so 
while it may sound like a broken record, temps along the coastline 
will be significantly cooler. 

Ridge breaks down as trough develops over the eastern CONUS Wednesday-
Friday. CMC, GEFS, and ECMWF remain at odds regarding how potent the 
trough will be, but a series of shortwaves and persistent low 
pressure located over the Great Lakes and a stalled frontal boundary 
will bring rounds of showers to southern New England Wednesday 
through the weekend. Ensemble probs aren't particularly remarkable 
when it comes to QPF, with just 20-50% probs of 0.5" QPF over any 24 
hour period, but onshore flow will make for a prolonged period of 
stratus and shower chances with temperatures locked in the upper 50s 
and low 60s. 

&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...

Forecast Confidence Levels:

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

18z TAF Update...

This afternoon and tonight...High Confidence in trends, but
more uncertainty in regards to specific timing.

MVFR ceilings along the coast this afternoon will gradually
spread westward tonight...eventually covering the entire region.
We also expect some IFR conditions to develop overnight with 
even localized LIFR cigs/vsbys in the high terrain. Light E 
winds.

Sunday...Moderate Confidence.

IFR/MVFR ceilings will trend to mainly MVFR thresholds with 
some diurnal heating despite the cloudy skies. Some showers will 
work into mainly interior MA & CT during the afternoon hours, but 
will not reach the coastal plain until late Sunday 
afternoon/evening. SE winds 5 to 10 knots.

Sunday night...Moderate Confidence.

Conditions should lower to mainly IFR with localized LIFR
cigs/vsbys given the cooling boundary layer Sunday night. 
A round of widespread showers will overspread the region from 
west to east Sunday night too. SE winds shift to more of a S 
direction at 5 to 10 knots.

KBOS TAF...High confidence in trends but more uncertainty in
regards to specific timing.

KBDL TAF...High confidence in trends but more uncertainty in
regards to specific timing.

Outlook /Monday through Thursday/... 

Monday: Mainly VFR, with local IFR possible. Chance SHRA.

Monday Night through Tuesday: VFR. Slight chance SHRA.

Tuesday Night: VFR. Chance SHRA.

Wednesday: Mainly VFR, with areas MVFR possible. Chance SHRA,
isolated TSRA.

Wednesday Night: MVFR/IFR conditions possible. Chance SHRA.

Thursday: Mainly VFR, with local IFR possible. Chance SHRA.

&&

.MARINE...

Forecaster Confidence Levels:

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

Tonight through Sunday night...High Confidence.

High pressure in the vicinity of the Canadian Maritimes tonight will 
shift east of there on Sunday. This as a shortwave energy approaches 
from the west late Sunday and Sunday night. That being said...the 
pressure gradient remains rather weak so winds/seas will remain 
below small craft advisory thresholds through Sunday night. E winds 
5 to 15 knots tonight shift to the SE Sunday and then more to the S 
on Sunday night. 
 
Outlook /Monday through Thursday/... 

Monday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers. Local visibility 1 nm or less.

Monday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers. 

Tuesday: Winds less than 25 kt. Slight chance of rain showers. 

Tuesday Night through Thursday: Winds less than 25 kt. Chance
of rain showers. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$

SYNOPSIS...Frank/KS
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...KS
AVIATION...Frank/KS
MARINE...Frank/KS