Lexington Weather

Lexington, Massachusetts, USA

66°F

5/20/2024 3:51pm

Lexington Conditions: Clear
Temperature: 66.0°F / 18.9°C
Dew Point: 57.2°F
Relative Humidity: 73%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.98 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 140529
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
129 AM EDT Tue May 14 2024

.SYNOPSIS...
A warm front brings widely scattered showers tonight followed 
by much warm weather tomorrow, a couple of showers and/or an
isolated thundershower are possible in the interior Tuesday 
afternoon. Unsettled weather Wednesday through the weekend with
more clouds than sun and periods of rain. Seasonable 
temperatures through the upcoming weekend.

&&

.NEAR TERM /THROUGH TODAY/...
930 PM Update...

Shower activity attempting to encroach on western MA and eastern
NY is having a tough time reaching the surface with dewpoint
depressions between 10-15F. Dewpoint depressions will shrink
overnight which will likely allow some light shower activity to
skirt north of the MA Turnpike before daybreak. 

Cloud cover is significantly less than forecast across the CT
River Valley per satellite, which may aid a bit in dewpoint
depressions collapsing over the next few hours, though S/SW
winds are just strong enough to stave off significant
radiational cooling. We'll see if this translates to slightly 
more widespread shower activity, but for now, kept forecast PoPs
as is. 


Previous Update...

Update: 3PM

Overall a stunner of an afternoon with many enjoying a sun-filled
afternoon while others are stuck beneath diurnal cumulus which 
developed along the sea-breeze boundary. As these diurnal clouds
wane this afternoon, mid and high clouds increase from the west
ahead of a warm front. Stepping outside this evening should 
enjoy temperatures in the low 60s and falling into the upper 50s
shortly after sunset. 850mb jet advects higher PWATs between 
1.0 and 1.3 inch tonight and with the warm front passing through
a few showers possible, though the best forcing looks to be 
limited to northern Massachusetts and points north into Vermont 
& New Hampshire. No washouts are expected, QPF is in the 
neighborhood of a few hundredths of an inch. South to southwest 
winds overnight are less than 10 mph. Nighttime lows are on 
either side of 50 degrees.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/...
Update: 3PM

A warm and summer-like head is on tap! With the passage of the warm 
front Monday night, we are placed in the warm sector. Clouds from 
overnight do linger across northern Massachusetts, but will give way 
to partly sunny skies and fairly mild temperatures. Deep southwest 
flow usher in warmer and a more humid air mass. 925mb temperatures 
climb to +14C to +18C and BUFKIT shows a well mixed boundary layer 
tomorrow, highs will easily climb into the middle 70s away from the 
coast. It's not out of the question a few spots like the Merrimack 
and Connecticut River Valley top out around 80 degrees. Back to the 
coast, the southwest flow is an onshore wind for coastal Rhode 
Island and southeast Massachusetts, here the temperature Tuesday 
afternoon only reaches the upper 60s and low 70s. Southwest winds 
become gusty as well, 15 to 25 mph. Shower are limited to northwest 
Massachusetts during the late afternoon where the best moisture and 
instability are located. HREF ensembles have roughly 500-1000 units 
of MUCAPE along and west of the Berkshires, so it's possible there 
may be an iso. non severe thunderstorm. Rain chances expand 
throughout the overnight hours with a mid-level trough and frontal 
boundary approaching from the west. Winds ease overnight becoming 
more south less than 10 mph. Night lows fall into the middle and 
upper 50s.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Update: 3PM

Highlights

* Unsettled weather Wednesday through the weekend with more clouds 
  than sun and periods of rain

* Seasonable temperatures through the weekend

Wednesday and Thursday

A coastal low pressure system will pass well south of southern New 
England during the day Wednesday. Nonetheless, modest synoptic 
forcing and PWATs greater than 1 inch should support periods of rain 
during the day Wednesday. Accumulations will be modest with the 
strongest forcing to our south, but somewhere between 0.1 and 0.25 
inches between Wednesday and Thursday morning should be in the cards 
for portions of southern New England. Downstream blocking has 
resulted in model guidance trending toward a slower departure of 
this system with cloud cover and showers lingering into the first 
half of Thursday for much of the forecast area. A mid-level ridge 
building in from the west may salvage a partly sunny day for the 
western areas on Thursday afternoon. Expect somewhat gusty southwest 
winds on Wednesday with northeast gusts along the east coast on 
Thursday. 

Friday through the weekend

The forecast remains unsettled late week through the weekend. As the 
mid-week coastal low departs over the Atlantic Friday afternoon, a 
short-wave dropping down from The Great Lakes will support the 
development of another surface low-pressure system that is likely to 
bring cloudiness and periods of rain to southern New England this 
weekend. Confidence in timing, duration, and intensity of potential 
rainfall is low at this time so we have leaned on the NBM for 
guidance at this time range. Temperatures look to be seasonably 
persistent through the weekend with daily lows in the low to mid 50s 
and daily highs ranging from the low 60s to low 70s. Coastal 
locations continue to run cooler  with highs in the upper 50s/low 
60s more common on days with onshore flow.

&&

.AVIATION /05Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:

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

06Z TAF Update

Tonight...High confidence.

VFR. Scattered showers are possible across northern MA, with at
times briefly lower VFR CIGs 3-5k ft. Winds are south to
southwest 5 to 10 knots.

Today...High confidence.

VFR. Very isolated showers through 12Z, generally north of the
MA Turnpike, resulting in little more than a wet runway. Dry
through mid day before the chance for isolated shower/thunderstorm
redevelops after 22Z in far western MA. Most terminals will
remain dry through the duration of the day. Steady southwest 
winds with gusts developing in the afternoon 20 to 25 knots. 

Tonight...High confidence. 

VFR with lowering cigs to around 4000-5000ft in western MA/CT by
daybreak where isolated showers are possible. Winds remain
persistent from the S/SW overnight. 

Wednesday... Moderate Confidence 

Tricky forecast Wednesday with low pressure to our south, but
drier trend has developed. Generally VFR with pockets of MVFR. Isolated
shower chances persist for western MA/CT but a mix of sun and 
clouds for eastern terminals. Showers associated with low 
pressure will remain south until early evening but may impact 
Cape/Islands/srn RI terminals by 00Z. S/SW winds shift to the 
SE. 

KBOS TAF...High confidence in TAF. 

VFR. Isolated shower chance before 12Z this morning. Breezy 
southwest winds with gusts 20 to 25 knots fend off any sea-
breeze potential on Tuesday. 


KBDL TAF...High confidence in TAF. 

VFR. Increasing wind speeds Tuesday with gusts 20 to 25 knots 
possible. Isolated shower chances late this evening.

Outlook /Wednesday Night through Saturday/... 

Wednesday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA.

Thursday: Mainly VFR, with local MVFR possible. Windy with
local gusts up to 30 kt. Chance SHRA.

Thursday Night: VFR. Breezy. Chance SHRA.

Friday: VFR. Breezy. Slight chance SHRA.

Friday Night: VFR. Chance SHRA.

Saturday through Saturday Night: Mainly VFR, with local IFR
possible. Chance SHRA.

Sunday: Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Update: 3 AM

Through Wednesday....


S/SW winds persist through Tuesday night before shifting to the
SE Wednesday afternoon. Gusts to 25kt possible this afternoon
for our far NE waters, resulting in a short fused small craft
advisory. Generally dry on Tuesday with isolated shower chances
for the eastern waters this morning. Shower chances increase 
for the southern waters late Wednesday as low pressure creeps 
north from the mid- Atlantic coast.

Outlook /Wednesday Night 
through Saturday/... 

Wednesday Night: Winds less than 25 kt. Local rough seas.
Chance of rain showers. 

Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas. Chance of rain showers.

Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas. Chance of rain showers.

Friday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. Slight chance of rain showers. 

Friday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers. 

Saturday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers. 

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

Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers.

&&

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

&&

$$

SYNOPSIS...Dooley/RM
NEAR TERM...Dooley/KS
SHORT TERM...Dooley
LONG TERM...RM
AVIATION...KS
MARINE...Dooley/RM