Lexington Weather

Lexington, Massachusetts, USA

57°F

5/10/2024 11:24am

Lexington Conditions: Few Clouds
Temperature: 56.8°F / 13.8°C
Dew Point: 41.4°F
Relative Humidity: 56%
Wind: Calm, 10-min avg: Calm, gust: 2 mph
Barometer: 29.77 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 101411
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1011 AM EDT Fri May 10 2024

.SYNOPSIS...
Low pressure tracks well south and east of New England through 
Saturday as high pressure builds in from the north. This will bring 
drier conditions after any lingering shower this morning, but cool 
temperatures as a persistent NE wind prevails. Continued cooler than 
normal Sunday with chance of showers as an upper level low pressure 
moves into the region. Milder temperatures return next week but an 
unsettled pattern persists through midweek.

&&

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

10 am Update:

Dry air has arrived from the north allowing for some significant
clearing especially over northern Massachusetts. This has also 
pushed showers further south and offshore which will be the case
for the rest of the day. 

Previous discussion:

Mid level trough moves into New Eng today as low pres moves off
mid Atlc coast and tracks well to the south. Modest forcing 
ahead of the mid level trough combined with area of deep 
moisture is resulting in showers pushing into SNE early this 
morning, mainly south of the MA Pike. A few showers will linger 
here this morning after daybreak, but expect a drying trend 
thereafter as low level drier air moves in from the north and 
east. While lots of cloud cover is expected today, this drier 
air will likely lead to partial sunshine developing later this 
morning into the afternoon, especially across eastern MA. NE 
flow and pocket of cold temps aloft with 850 mb temps falling to
near 0C will keep temps in the mid-upper 50s today, except 
lower 60s CT valley. This is about 10 degrees below normal. NE 
winds 10-20 mph expected with some higher gusts possible along 
the south coast where weak low level jet present.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Tonight...

Mid level trough moves south and east of New Eng with further 
drying from the north as PWATs drop below 0.50". Partial 
clearing expected overnight in the interior, but more clouds 
will linger near the coast. Decent radiational cooling may 
develop in the interior as winds decouple. This may result in 
lows dropping into the upper 30s in portions of the interior, 
with low-mid 40s elsewhere. 

Saturday...

Weak shortwave ridging develops across SNE between departing 
shortwave to the east and upstream trough moving into the Gt 
Lakes. This will maintain surface high pres with mainly dry 
conditions and partial sunshine, although can't rule out a spot
shower in eastern MA with marginally cold temps aloft and steep
low level lapse rates with lingering low level moisture. 
Another cool day with temps several degrees below normal as 850
mb temps 0 to -1C. Expected highs will be in the mid-upper 50s 
with lower 60s in the CT valley.

&&

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

* Unseasonably cool and mainly dry Sunday 

* Temps become more seasonable Monday and Tuesday

* Unsettled wet weather Monday - Wednesday, but uncertainty remains 
  high.

Sunday:

Upper level closed low becomes centered over SNE. This leaves the 
region under cyclonic flow along with a cold pool aloft. The best 
forcing with the closed low remains south of SNE. There is a low 
chance for a weak hit or miss diurnally driven showers Sunday, 
however, guidance doesnt show much if any instability and bufkit 
soundings show a rather capped atmosphere with some warming at 
700mb. Skies look to turn mostly cloudy Sunday with onshore flow and 
a moist column. High temps remain unseasonably cool in the upper 50s 
to low 60s with 850mb temps still around -1C.

Monday - Wednesday

Upper level closed low and cold pool finally move to the NE. 850mb 
temps quickly begin to warm to +7C by Monday. This will allow 
temperatures to become more seasonable with highs in the low to mid 
70s. Precipitation is rather messy during this time period with 
considerable uncertainty. Monday should be mainly dry for the most 
part with rising heights. However, WAA and PWATS near 1.1 inches 
enter the region and could bring a few weak showers late in the day. 
Better forcing doesnt look to arrive until late Tuesday night into 
Wednesday as a weakening shortwave exiting the Great Plains sends 
weak impulses of energy along with falling heights to the region. 
The best forcing from this shortwave once again looks to stay south 
of the region sending most of the widespread rain south as well. 
Ensemble guidance remains very spread out with this system with very 
little agreement between the GEFS and Euro members.  Using the LREF, 
which combines the GFS, Euro, and Canadian ensembles, 24 hour 
probabilities for 0.5 inches of rain max out Wednesday at 40-50% 
along the south coast, with 30% or less further north.  

Thursday and Friday

A very dry airmass looks to follow behind the shortwave with PWATS 
falling below 0.4 inches. An upper level ridge and rising heights 
should allow skies to be mostly sunny. Weak CAA and NW winds should 
keep daytime high temps in the low to mid 70s.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

12z Update:

An area of light showers is moving across the Cape and Islands 
this morning and should come to an end around 14z. Any leftover
MVFR ceilings should become VFR after 14z. 

Today...High confidence.

MVFR-VFR cigs trending to VFR from NE to SW. A few showers  
south of the MA Pike into early afternoon. NE wind 10-20 kt with
higher gusts over the Islands. 

Tonight...High confidence.

VFR, except for ACK where MVFR cigs possible with low chance of
a few showers. NE wind 5-15 kt becoming N overnight. 

Saturday...High confidence.

VFR, but areas of MVFR cigs developing across portions of eastern
MA and Cape/Islands where a spot shower possible. NE wind 10-20
kt.

KBOS TAF...High confidence in TAF. 

KBDL TAF...High confidence in TAF. MVFR cigs this morning with
scattered showers will improve this afternoon. 

Outlook /Saturday Night through Tuesday/... 

Saturday Night: Mainly VFR, with local MVFR possible. 

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

Sunday Night: VFR. 

Monday: VFR. Breezy. 

Monday Night: VFR. Breezy. Slight chance SHRA.

Tuesday: VFR. Breezy. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Saturday...

Low pres tracking south and east of the waters will bring NE 
winds 10-20 kt with occasional 25 kt gusts over southern waters
through Sat with seas building to 5 ft. Extended the SCA for 
outer southern waters through Sat. 

Outlook /Saturday Night through Tuesday/... 

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

Sunday through Sunday Night: Winds less than 25 kt. Areas of
seas approaching 5 ft. 

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

Monday Night: Low risk for Small Craft Advisory winds with
gusts up to 20 kt. Areas of seas approaching 5 ft. 

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 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 Saturday for ANZ254>256.

&&

$$

SYNOPSIS...KJC/KP
NEAR TERM...KJC/BW/KP
SHORT TERM...KJC
LONG TERM...KP
AVIATION...KJC/KP
MARINE...KJC/KP