Lexington Weather

Lexington, Massachusetts, USA

48°F

4/20/2024 1:40am

Lexington Conditions: Overcast
Temperature: 48.0°F / 8.9°C
Dew Point: 42.1°F
Relative Humidity: 80%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.96 in Falling Slowly
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 130627
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
227 AM EDT Sat Apr 13 2024

.SYNOPSIS...
An occluded front will sweep across the region late this
afternoon and evening, accompanied by a wind shift to the
southwest along with drier and cooler air. The front will be
accompanied by scattered showers, especially in CT and western-
central MA. It will remain mostly cloudy tonight and Saturday,
along with turning seasonably cool. Sunday is largely dry and  
comfortable, a quick moving system does bring showers late 
Sunday and exits before sunrise on Monday. Early next week 
features dry and above normal temperatures. Mid to late next 
week the forecast becomes unsettled with rain chances.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
1000 PM Update: 

Much quieter weather conditions tonight compared to last
night/Friday morning! Satellite reveals mostly clear skies in 
SNE currently and there are still some SWly breezes around 10-15
mph with occasional 25 mph gusts keeping current temps in the 
upper 40s to mid 50s. Despite the mostly clear skies, 
expectation of cold air stratocu moving back in across at least 
interior MA and CT still looks valid as upper low and associated
cold pocket of air aloft begins to make greater eastward 
inroads into SNE. Though there could be a shower or two 
underneath this cloud layer, should be the exception than the 
rule. Some cooling is expected tonight but with the breezes 
staying up for much of the night and the anticipated increase in
cloud cover toward overnight/early morning, should be 
predominantly in the 40s.

Previous update from 750 PM follows:

No whole sale changes to the forecast. The area did get a nice 
break in the clouds prior to sunset, now looking at mostly clear
conditions across much of the CWA. Did adjust the sky cover as 
result, but think more clouds will filter back across western 
Massachusetts and Connecticut later tonight. Winds are still
mostly south, but are starting to make more of a turn to the
south/southwest - this will continue tonight with periods of
gusty winds.

Previous discussion below.... 

345 PM update:

Occluded front moving into southwest CT at 330 pm. This feature
is accompanied by a cluster of showers moving SW to NE thru CT
and into western-central MA. Showers will be much less numerous
in RI and eastern MA late this afternoon/early evening. Despite
western MA being in a marginal risk from SPC, current thinking
is the limited instability will preclude any storms from forming
and any thunderstorms confined to much farther north across VT
and upstate NY, north of Albany. 

The front will also be accompanied by a wind shift from SSE to 
the SW, ushering in drier and cooler air. In fact, the core of 
the cold air aloft (-26C at 500 mb) advects across SNE between 
06z-09z. This could trigger an isolated shower overnight, 
otherwise mainly dry weather prevails in the post frontal 
airmass. Despite the cold air aloft, lows only dip into the 40s 
overnight, about 10 degs above normal. Dew pts only drop into 
the 40s as well, also above normal for mid April, but there 
should be sufficient wind/mixing to preclude any fog. Hence, 
remaining breezy behind the front, with SW winds 15-25 mph.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
345 PM update:

Saturday:

Good mixing via WSW winds 15-25 mph, gusting up to 30 mph along
the south coast including Cape Cod and the Islands. This
promotes drier air aloft to mix to the surface, with dew pts
falling into the 30s. Cyclonic flow will yield lots of clouds,
mostly cloudy the likely scenario. Best chance for sunny breaks
will be over southeast MA, including Cape Cod and Islands. Temps
begin to warm aloft during the day, this should limit
instability shower coverage to isolated, hence a mostly dry 
day. The exception will be across western MA, where upslope flow
over the Berkshires will yield more numerous showers for 
western MA. 

Temps seasonable Saturday, with highs in the mid to upper 50s.
Although, there will be a cool breeze as noted above, from the
WSW 15-25 mph, higher gusts south coast MA/RI. 

Saturday night...

Short wave ridging and warming temps aloft will promote
decreasing cloudiness. Thus, dry weather prevails. Gusty west
winds 15-25 mph during the evening, slowly slacken overnight.
Seasonably cool with lows in the upper 30s and lower 40s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
345 PM update...

Highlights: 

* Dry for much of Sunday, but a quick moving system will bring 
  showers late evening and wrapping up predawn Monday. 

* Early next week, Monday and Tuesday, features dry conditions and 
  above normal temperatures.

* Unsettled conditions return to the region by mid/late next week.  

Sunday and Sunday Night - Brief mid-level ridging and surface high 
pressure noses north, leading to an all around a nice day with 
sunshine during the first-half of the day, but increasing cloud 
cover during the afternoon ahead of a fast moving low pressure 
system coming out of the northern Great Lakes. Afternoon 
temperatures are pretty comfortable, 850mb temperatures are +2C to 
+5C, with a well mixed boundary layer, expect highs in the upper-50s 
to lower-60s. Winds do increase during the afternoon as well due to 
a quick moving 925mb LLJ, while the core is primarily over southern 
Rhode Island and southeastern Massachusetts, southwest gusts are in 
the range of 20 and 30 MPH, interior winds are generally around 15 
to 20 MPH. Most if not all of the daylight hours remain dry, it is 
not until the late afternoon/early evening we introduce POPs across 
far western zones. PWATs are fairly healthy around 0.8 and 1.1 inch, 
the best forcing does remain north across northern New England. Do 
think there will be terrain enhancement for the Berkshires, leading 
to little more in the way of rainfall overnight. With some MUCAPE 
don't be surprised if there are some rumbles of thunder - SPC does 
have areas west of Hartford and Springfield under general thunder in 
its day three outlook. Surface low pressure system is progressive 
and exits east of the coastal waters before dawn on Monday. QPF is 
less than a tenth of an inch across much of the CWA, with slightly 
higher values for the eastern slopes of the Berkshires where two 
tenths of an inch is possible. 

Monday - Low pressure system races east of the coastal waters with a 
drier air mass aloft moving into the region. Clouds to start, though 
expect morning clouds gives way to a mostly sunny Patriots Day. Made 
an adjustment to sky cover, as NBM held onto higher values of sky 
cover despite the mid-levels drying. Also lowered wind gusts due to 
the high bias NBM, had gusts 20 to 25 knots. BUFKIT showed winds at 
the top of the boundary layer generally between 12 and 17 knots, did 
blend in the CONSALL guidance to temper those gusts down. Northwest 
winds 10 mph with occasional gusts 15 to 20 mph. With the winds at 
the top of the boundary layer greater than 10 knots, the threat for 
a sea breeze at Boston remains low. Temperatures climb once again 
into the 60s, perhaps reaching the 70 degree mark due to the dry 
atmosphere and pre-greenup conditions, recipe to have over 
performing temperatures. 

Tuesday - Another stunning day thanks to surface high pressure to 
the south and mid-level ridging aloft. Do think our conditions will 
be similar to Monday, though slightly more of a WNW breeze. Mostly 
sunny conditions and highs in the 60s to near 70 degrees. As 
mentioned on Monday, this pre-greenup period and dry atmosphere 
could allow the highs to sneak up into the lower-70s.

Wednesday and Thursday - This period does look unsettled as the 
global models have a developing surface low pressure system in the 
central plains on Tuesday that races towards the Great Lakes. 
Perhaps a warm front develops with showers on Wednesday with a 
trailing cold front on Thursday. Still a lot of time between now and 
then. Have run with POPs of Chance due to the uncertainty at this 
point in time.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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

06Z TAF Update:

Through 12z Saturday: High confidence. 

VFR; however clouds will be increasing both in coverage and 
lowering in bases into the VFR/MVFR range toward daybreak in 
western MA/CT. S to SW winds around 10 kt.

Today: High confidence. 

BKN/OVC VFR to MVFR cloud bases (bases 015-040) with hit or 
miss light diurnal showers. Strongest chance at MVFR bases 
along and west of PVD to BED line, though BOS could see 
periodic MVFR bases. Bases should trend toward SCT-BKN VFR/MVFR
later in the day. Turning blustery with winds 25-35 kt from the
SW to WSW/W, but gusts could be as much as 40 kt at BAF and 
ORH.

Tonight: High confidence. 

VFR with decreasing cloudiness. West winds around 10-13 kt with
easing gusts.

Sunday: High confidence in trends, though moderate in timing
showers. 

Quick-moving frontal system from the Great Lakes spreads
increasing/lowering cloud bases into the VFR/MVFR range. Best
chance of scattered showers during the afternoon after 18z;
there could be a rumble or two of thunder south and west of a
BDL-PVD line later in the day but this is not set in stone. W
winds shift to SW then S around 10-12 kt.

KBOS TAF...High confidence in TAF. Mainly BKN VFR to at-times
MVFR bases (thinking 025-040). Could be a hit or miss shower 
but not enough confidence in coverage to include as a TAF 
mention. Bases should trend VFR by late afternoon to tonight. SW
winds increase around 15 kt with gusts 25 kt, then becoming W 
and decreasing to around 10-12 kt tonight.

KBDL TAF...High confidence in TAF. BKN to OVC VFR bases trend
MVFR early this morning, with periodic P6SM -SHRA. Bases start
to lift towards VFR levels tonight. S winds around 10 kt to
start, then shift to SW/WSW and increase to around 10-14 kt with
gusts 25-28 kt late AM to aftn, easing to 10 kt tonight. 

Outlook /Sunday Night through Wednesday/... 

Sunday: VFR. Breezy. Slight chance SHRA.

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

Monday through Monday Night: VFR. 

Tuesday: VFR. Breezy. 

Tuesday Night: VFR. 

Wednesday: VFR. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

1055 PM Update:

Latest forecasts now indicate a 5 to 10 kt increase in expected
WSW wind gusts for the southern waters on Saturday, with a 
950-925 mb SW jet of 35 to 45 kt. This had necessitated issuance
of Gale Warnings for all southern waters with gusts up to 35 
kt. Gale warnings will eventually need to be downshifted to 
small craft advisories as winds subside. The jet is weaker 
across the northern waters, and opted for small craft advisories
for these waters for Saturday.

Outlook /Sunday Night through Wednesday/... 

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

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

Monday: Winds less than 25 kt. Local rough seas. 

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

Tuesday through Tuesday Night: Winds less than 25 kt. 

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 AM this morning to 8 PM EDT this 
     evening for ANZ230-236.
     Small Craft Advisory until 8 AM EDT Sunday for ANZ231-250-251.
     Gale Warning until 2 AM EDT Sunday for ANZ232-256.
     Gale Warning until 8 PM EDT this evening for ANZ233>235-237.
     Gale Warning until 5 AM EDT Sunday for ANZ254-255.

&&

$$

SYNOPSIS...Nocera/Dooley
NEAR TERM...Loconto/Nocera/Dooley
SHORT TERM...Nocera
LONG TERM...Dooley
AVIATION...Loconto/KS
MARINE...Loconto/KS