Lexington Weather

Lexington, Massachusetts, USA

54°F

5/11/2024 1:51pm

Lexington Conditions: Overcast
Temperature: 54.1°F / 12.3°C
Dew Point: 44.6°F
Relative Humidity: 70%
Wind: Calm, 10-min avg: Calm, gust: 1 mph
Barometer: 29.82 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 051248
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
848 AM EDT Sun May 5 2024

.SYNOPSIS...
Cloudy and cool weather is on tap for today with a period of 
widespread showers arriving from the west this afternoon and
continuing overnight. Mild and dry to start the work week 
before cooler and unsettled conditions Wednesday through next 
weekend

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

845 AM Update...

* Cloudy with showers moving into the interior mainly this
  afternoon & late afternoon/early evening on I-95 corridor

* Remaining cool this afternoon with highs only in the 50s

Previous forecast is pretty much on track. High pressure over 
the Canadian Maritimes will continue to shift further east today
as shortwave energy approaches from the west. The
stronger/forcing deeper moisture will not impact the interior
until this afternoon. So while a few spot showers are possible
this morning across the interior...expect the main threat of
showers to arrive this afternoon. Meanwhile...in the Boston to
Providence corridor the showers should not arrive until late
afternoon/early evening but it still will be cloudy.

As for temperatures...they will remain cool today with cloudy
skies and onshore low level flow. This should keep high
temperatures in the 50s across the vast majority of the region. 

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...

Tonight

Showers associated with an upper-level short-wave traversing over 
The Northeast spread west to east this evening. Expect widespread 
light showers across southern New England with new rainfall 
accumulations totaling 0.25 to 0.5 inches. Winds remain steady out 
of the south which will keep dewpoints elevated and support some 
patchy fog formation. Low temps will be bottom out early in the 
evening as southerly flow and low-level warm advection will begin to 
support increasing temperatures after midnight and into tomorrow 
morning.

Tomorrow

A substantial warm up tomorrow as southerly flow advects a near 15C 
air mass at 925 hPa over the region. Still expecting a good amount 
of low to mid-level cloud cover across the region for the first half 
of the day, but breaks of sun in the afternoon should support warm 
temperatures in the low to mid 70s across areas of southern New 
England away from the coast. Winds may be light enough to support a 
sea-breeze along the coastline which would result in cooler 
temperatures in the mid 60s.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
* Dry with warmer than normal temperatures Tuesday

* Cooler with periodic showers Wednesday thru Saturday

Temperatures...

Warm airmass over SNE with good model consensus of 925 mb temps 
ranging from +16C to +18C...and +10C at 850 mb. These temps aloft 
combined with good blyr mixing via strong/high May sun angle and a 
dry airmass (dew pts in the 40s) will support highs 75-80. Ensembles 
have 100% probability of 70+ temps away from the immediate coast 
Tue. These temps are much warmer than normal (60s) for early May. 
Thus, a dry heat for Tue. A weak pressure gradient combined with 
ocean temps in the 40s, will result in a wicked seabreeze, hence 
much cooler along the coast, Cape and Islands. However, coastal 
locations including Boston, could briefly hit 70+ before the 
seabreeze arrives. Nonetheless, Tue definitely the pick of the week, 
then a pattern change develops around Wednesday and continues thru 
next weekend. A stalled frontal boundary sets up over or near SNE, 
yielding a cooler regime, with lots of clouds, onshore flow and risk 
of showers from time to time. Temps likely become progressively 
cooler each day, beginning Wed and continuing into next weekend. 

Precipitation...

Any leftover scattered showers Monday evening associated with weak 
cold front, quickly come to an end as post frontal airmass 
overspreads the region later in the evening and overnight. Turning 
less humid Monday night, as dew pts fall from 55-60 into the upper 
40s/low 50s by 12z Tue. Dry NW flow prevails Tue followed by a 
pattern change with a stalled frontal boundary setting up over or 
near SNE, beginning Wed and continuing into next weekend. Lots of 
uncertainty on the exact placement of this boundary and timing and 
amplitude of frontal waves traversing this boundary. There will be 
periods of dry weather during this time as well, hence not raining 
every hour of the day.

&&

.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

12z TAF Update...

Marginal MVFR/IFR will slowly lift to mainly MVFR but then
likely lower this afternoon and especially late in the day as
showers overspread the region from west to east. Light E-SE
winds. Earlier discussion below. 

---------------------------------------------------------------

Borderline IFR/MVFR ceilings between 008-012 feet with light
easterly winds. 

Sunday...High 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.

IFR/LIFR ceilings develop with light showers spreading west to
east across southern New England overnight. SE winds shift to 
more of a S direction at 5 to 10 knots.

Monday...

IFR ceilings lifting to VFR levels by late morning/early
afternoon. Though lower IFR ceilings may persist longer over 
The Cape Islands. Light southwest winds becoming more westerly.
Winds may be weak enough to support a sea-breeze circulation
along the coastline. 

KBOS TAF...High confidence 

KBDL TAF...High confidence 

Outlook /Monday Night through Thursday/... 

Monday Night through Tuesday: VFR. 

Tuesday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA.

Wednesday: Mainly MVFR, with local IFR possible. Breezy. Chance
SHRA, isolated TSRA.

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

Thursday: Mainly VFR, with areas MVFR possible. Breezy. Chance
SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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


Today through Tomorrow

Seas increase by about a foot over the next 48 hours as winds become 
more steady out of the south. Nonetheless, conditions remain on the 
quiet side with wind speeds topping out at 10-15 knots and seas in 
the 2 to 4 foot range. A period of stronger gusts up to 20 knots is 
expected to develop tomorrow afternoon over the outer southeastern 
marine zones. 

Outlook /Monday Night through Thursday/... 

Monday Night: Winds less than 25 kt. Seas locally approaching
5 ft. 

Tuesday through Tuesday Night: Winds less than 25 kt. 

Wednesday: Winds less than 25 kt. Chance of rain showers,
isolated thunderstorms. 

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

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

&&

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

&&

$$

SYNOPSIS...Nocera/RM
NEAR TERM...Frank
SHORT TERM...RM
LONG TERM...Nocera
AVIATION...Nocera/RM
MARINE...Nocera/RM