Lexington Weather

Lexington, Massachusetts, USA

66°F

5/20/2024 2:26pm

Lexington Conditions: Few Clouds
Temperature: 66.4°F / 19.1°C
Dew Point: 57.0°F
Relative Humidity: 72%
Wind: SW 4 mph, 10-min avg: 1 mph, gust: 7 mph
Barometer: 29.99 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 142308
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
708 PM EDT Tue May 14 2024

.SYNOPSIS...

High pressure offshore provides mild conditions and mainly dry
weather tonight and Wednesday. Although, can't rule out a few
brief showers at any given time, especially across CT and
western-central MA. Low pressure passing to our south will 
likely result in a period of showers for the first half of 
Thursday...at least south of the Massachusetts Turnpike. 
Otherwise...dry weather should dominate Friday through the 
weekend other than a spot shower or two. Temperatures will 
average below normal especially along the immediate coast with 
onshore flow Thursday through the weekend...but a warming trend 
is expected early next week.

&&

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

7 PM Update...

* Increasing clouds & mild overnight with lows in the 50s
* A few showers possible toward daybreak in western MA/CT

Lingering upper level ridging across southern New England has 
kept the scattered diurnal showers to our north and west today.
This ridging will gradually slide further east tonight allowing
for increasing mid-high level cloudiness to overspread
the region from shortwave energy across the Ohio Valley. 
Still expect dry weather to generally prevail...but warm 
advection will probably be enough for a few showers to 
develop toward daybreak across western MA/CT. Previous 
forecast handles this well in the next paragraph. 

With sunset SSW winds will begin to diminish. Scattered showers
over NYS will likely erode as the activity moves east into
drier/more stable airmass over SNE. However, later tonight as
closed low currently over TN/OH valley advects eastward,
deepening moisture and forcing for ascent will increase
somewhat, yielding a low risk for a few showers overnight across
CT into western-central MA. Otherwise a dry and mild night
ahead, with lows only in the 50s, above normal for mid May.

&&

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

Wednesday...

Enough ridging may linger for a mostly dry day, especially 
across RI and eastern MA. A few showers possible across CT into
western-central MA, where some differential heating across the
hilly terrain may be in play. Otherwise, a mainly dry day with  
even be some sunshine Wed across RI and eastern MA, more clouds
westward into CT and western/central MA. This partial sunshine 
will combine with warm temps aloft and yield highs 70-75, 60s 
along the coast where light onshore flow/seabreeze develops. Dew
pts in the 50s will also provide a mild feel to the airmass. 

Wednesday night...

Closed low southwest of New England begins to circulate deeper
moisture and low level easterly jet into CT/RI and southeast 
MA. This is where the risk of rain is highest. Some uncertainty
how far north this rain shield will pivot, as mid level low
tracks ESE. Thus, rain shield may remain south of the Mass Pike.
Mild temps continue with lows in the 50s. Light south winds
become east by Thu morning.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...

Key Points...

* Showers likely the first part of Thu at least south of I-90
* Highs Thu-Sun...55-65 on immediate coast & 65-75 distant interior
* Mainly dry Fri/Sat/Sun...but clouds & a spot shower at times
* Warming trend likely early next week

Details...

Thursday...

Low pressure will be passing south of the Benchmark on Thu. There is 
uncertainty with the northern extent of the rain shield especially 
given limited baroclinicity this time of year...it can often be 
quite challenging. Current thinking is that we probably will see a 
period of showers during the first part of Thu...at least to the 
south of I-90. Later shifts will need to make adjustments depending 
on model trends. Onshore flow will likely hold high temps in the 
upper 50s to the lower 60s on the immediate coast & 60s/near 70 
further inland. 

Friday/Saturday/Sunday...

High pressure over the Canadian Maritimes will combined with a 
distant offshore low pressure system...Fri into the weekend. This 
will generate an onshore flow and keep temps cool/below normal 
especially along the immediate coast. Further inland...temps more 
tricky and dependent on the amount of solar insolation. There might 
be clouds at times with the onshore flow...but also periods of 
sunshine as drier air may get circulated around the high pressure in 
the Maritimes. Therefore...thinking high temps generally in the 55 
to 65 degree range along the immediate coast & between 65 and 75 
across the distant interior. 

High pressure nosing down from the Maritimes may be enough to keep 
most of the precipitation risk to our west and south Fri/Sat/Sun. We 
may see a spot shower or two...but overall thinking dry weather 
dominates. 

Early Next Week...

There are some indications that the upper level energy to our south 
will weaken and also get suppressed further south. This should allow 
for some rising height fields and warming temperatures. There is 
uncertainty as to how quick and to what magnitude this process may 
occur...but thinking a warming trend is in the cards.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...

Forecast Confidence Levels:

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

00z TAF Update...

Tonight...High Confidence.

Mainly VFR conditions prevail tonight despite increasing
mid-high level cloudiness from west to east. That being 
said...We may have to watch for low clouds and fog patches 
developing late near the Cape and Islands with increasing low 
level moisture and a cooling boundary layer. A few showers may 
develop toward daybreak across western MA/CT...but conditions 
should remain VFR to at worst marginal MVFR. Gusty winds 
diminish after sunset...but winds will remain S tonight but will
become rather light.

Wednesday...Moderate Confidence.

A broken deck of VFR-MVFR ceilings are expected with the
tendency for the lower conditions to be found across interior MA
& CT. Dry weather dominates...but a few showers are possible
mainly northwest of I-95. S winds 5 to 10 knots...but localized
sea breezes are possible during the afternoon along portions of
the immediate coast. 

Wednesday night...Moderate Confidence.

Light S-SE winds become east overnight. VFR conditions become
MVFR overnight, as rain shield comes onshore to the south coast
of CT/RI/MA. Forecast uncertainty in how far north this rain
shield tracks overnight. 

KBOS TAF...High confidence in TAF. The biggest uncertainly is
the potential for an ESE sea breeze for a time Wed afternoon.

KBDL TAF...High confidence in TAF.

Outlook /Thursday through Sunday/... 

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

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

Friday through Friday Night: VFR. Breezy. 

Saturday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance SHRA.

Saturday Night: Mainly MVFR, with areas IFR possible. Breezy.
Slight chance SHRA.

Sunday: Mainly MVFR, with local IFR possible. Breezy. Slight
chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

7 PM Update...

Tonight...

We will allow the near shore small craft headlines for SSW gusts
up to 25 knots to expire at 8 pm with the loss of diurnal
heating. Southerly winds should diminish. High pressure 
offshore provides mainly dry weather tonight, but patchy fog may
develop over the southern MA/RI waters. 

Wednesday...

Weak high pressure offshore results in light S-SE winds. Mainly
dry weather and any morning fog burns off by midday with good
vsby thereafter. 

Wednesday...

Low pressure south of New England drifts north, with increasing
east winds 15-20 kt toward Thu morning. Vsby lowers to 1-3 miles
in areas of fog and rain, especially southern MA and RI waters. 

Outlook /Wednesday Night 

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

Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Seas up to 5 ft. Slight chance of rain showers. 

Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. 

Saturday: Winds less than 25 kt. Seas up to 5 ft. 

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for 
     ANZ230>237-251.

&&

$$

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