Lexington Weather

Lexington, Massachusetts, USA

41°F

5/11/2024 3:06am

Lexington Conditions: Clear
Temperature: 41.2°F / 5.1°C
Dew Point: 37.0°F
Relative Humidity: 85%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.82 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 060511
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
111 AM EDT Mon May 6 2024

.SYNOPSIS...
A period of widespread showers impacts the region tonight with the 
focus for them this evening. Partial sunshine develops on Monday 
with much warmer temperatures. A brief band of scattered showers is 
expected Monday afternoon/evening...but the majority of the time 
will feature dry weather. Tuesday will be the pick of the week with 
abundant sunshine and above normal temperatures. Unsettled 
pattern develops for Wednesday and beyond with below normal 
temperatures. Some uncertainty revolves around the weekend 
forecast.

&&

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

1AM Update

Showers traversing across southern New England this evening are
moving a bit faster than expected and will be coming to an end
for hte areas across northeastern MA in the next hour or two.
Showers persist for a few more hours over the south coast,
southeastern MA, and RI before clearing out this morning. Made
some updates to reflect the faster departure of showers. The
rest of tonight's forecast remains unchanged. Expect some patchy
areas of fog to develop with light winds and plenty of moisture
in place prior to sunrise. 

Previous Update...

335 PM Update...

* Period of widespread showers tonight with the focus this evening
* Low temps between 45 and 50 with areas of fog developing

Approaching shortwave/mid level warm front was inducing a modest 
southwest low level jet this afternoon. This has allowed a band of 
widespread showers to overspread areas northwest of I-95. This band 
of showers will gradually sink southeast and impact the Boston to 
Providence corridor by late afternoon/early evening. Once the steady 
showers arrive they should generally last between 3 and 6 hours. The 
bulk of the showers will come to an end northwest of I-95 near or 
shortly after midnight...but linger towards the Cape and Islands. 

Overnight low temps should only drop a few degrees from their 
current readings...mainly in the 45 to 50 degree range. We do expect 
some fog to develop overnight given increasing low level moisture 
with light southerly flow.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
Key Points...

* Partial sunshine developing away from south coast Monday
* Turning much warmer with highs well into the 70s for most on Monday
* Scattered brief showers Mon PM, but most of the time it will be dry

Details...

Monday and Monday night...

Any lingering showers towards the Cape/Islands should come to an end 
Monday morning as the shortwave departs. Subsidence and enough 
westerly flow aloft should allow for partial sunshine to develop. 
Temperatures will quickly respond give 850T near +10C. It will be 
much warmer than today with highs well up into the 70s. May even 
feel a tad humid given dewpoints in the upper 50s to near 60...so 
quite the change. It will be cooler near the south coast, Cape and 
Islands where low clouds and fog patches may linger.

The vast majority of Monday will feature dry weather. However...a 
cold front dropping south will probably result in a band of brief 
scattered showers dropping south Monday afternoon and evening. There 
probably will be a few hundred J/KG of Cape developing...but mid 
level dry air advecting in from the west will limit potential. So 
while a rumble or two of thunder is possible...opted to keep out of 
the forecast for now. Later shifts may have to take another look. 
Low temps Monday night will mainly be in the upper 40s to the middle 
50s. There may be some patchy fog development too.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
* Dry and Mild on Tuesday

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

Tuesday continues to be the pick of the week, and while heights 
begin to fall as more zonal flow develops aloft, west/northwest 
downsloping boundary layer flow will support well above normal temps 
with 850mb temps between 7 and 9C and 925mb temps around 13C. Weak 
pressure gradient will lead to a seabreeze along the immediate 
coastline, so while temperatures soar into the mid and upper 70s 
across the interior, coastal localities will likely see peak temps 
in the late morning before temps drop back into the upper 50s/low 
60s by late afternoon. 

Synoptic shift towards a more zonal pattern on Wednesday and 
Thursday with a few shortwaves enhancing shower chances across 
southern New England. Robust trough develops over the eastern CONUS 
by Friday, allowing very unsettled pattern to persist through much 
of the weekend as low pressure remains nearly stationary over 
southern Ontario. Fortunately, the weak shortwaves wont bring 
tremendous rain chances to the region, with 7 Day QPF ensemble 
probabilities of 1" ranging between 40, SE MA, and 80, NW MA, 
percent through next Monday. While still a week out, the persistence 
of the pattern into late next weekend is a bit uncertain, with some 
global guidance, like the CMC and GFS, shifting the trough offshore 
late Saturday/early Sunday, which could yield improving conditions 
for the second half of the weekend.

Aside from scattered rain chances later this week, temperatures will 
be stuck below to well below normal thanks to aforementioned stalled 
front and very persistent onshore flow. Temps will be stuck in the 
50s most days across the eastern half of the CWA. Frontal boundary 
placement will make temperature forecasting a bit tricky for CT and 
western MA, where there are few opportunities late week for temps to 
climb into the 60s in that region.

&&

.AVIATION /05Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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


06Z TAF Update

Through 12Z...High Confidence

MVFR/IFR conditions persist through 12Z with patchy areas of fog
developing. -SHRA continues over The Cape/Islands with light
southeasterly winds.

Today...Moderate Confidence

MVFR/IFR conditions early should scatter out to VFR by 12-14Z
across the interior and at BOS. MVFR/IFR conditions persist over
the south coast, Cape, and Islands. Winds light out of the
west/southwest. Sea-breeze developing at BOS by mid to late
morning.

Tonight...High Confidence

MVFR/IFR conditions fill back in across the interior and persist
over the south coast, Cape, and Islands through about 06Z. Winds
shift to the north after that time frame and allow ceilings to
gradually improve to VFR by 09-12Z.

Tomorrow...High Confidence

VFR. Light northerly winds becoming light out of the west. Sea-
breezes likely along the coast with very warm temps forecast
over land. 


KBOS TAF...Moderate Confidence in TAF. BOS should scatter out
for a few hours this morning into early afternoon before
returning to MVFR by early to mid afternoon. Moderate 
confidence in a sea- breeze circulation developing today between
14 and 16Z. Higher confidence in a sea- breeze for Tuesday.

KBDL TAF...High Confidence in TAF.

Outlook /Tuesday Night through Friday/... 

Tuesday: VFR. Slight chance SHRA.

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

Wednesday: Mainly MVFR, with areas IFR possible. Breezy. SHRA
likely, isolated TSRA.

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

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

Thursday Night: MVFR/IFR conditions possible. Breezy. SHRA
likely, isolated TSRA.

Friday: MVFR/IFR conditions possible. Breezy. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight through Monday night...High Confidence.

A mid level warm front will cross the region tonight this will be 
followed by the passage of a weak cold front Monday night. 
However...the pressure gradient will remain relatively 
weak...keeping winds/seas below small craft advisory thresholds. We 
may have enough of a LLJ for some southerly wind gusts of around 20+ 
knots to develop very late tonight into Monday morning. Winds 
gradually shift to more of a W direction Monday afternoon and then 
NW Monday night...but well below small craft advisory thresholds. 
The main issue for mariners will be areas of fog developing 
overnight and persisting at times through Monday evening...until the 
cold frontal passage brings drier air and scours out the remaining 
fog. 

Outlook /Tuesday Night through Friday/... 

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

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

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

Wednesday Night: Winds less than 25 kt. Seas locally
approaching 5 ft. Chance of rain showers. 

Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers, isolated thunderstorms. 

Thursday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers, isolated thunderstorms. 

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

&&

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

&&

$$

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