Lexington Weather

Lexington, Massachusetts, USA

54°F
10/17/2021 8:18pm 
  • Lexington Conditions: Clear
  • Temperature: 53.6°F / 12.0°C
  • Dew Point: 47.8°F
  • Relative Humidity: 81%
  • Wind: Wind from SW SW Calm, 10-min avg: 1 mph, gust: 3 mph
  • Barometer: 29.66 in Steady
  • Visibility: 10 miles
  • Rain Today: 0.35 in
  •   

Area Forecast Discussion
for Boston, MA

        
000
FXUS61 KBOX 170551
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
151 AM EDT Sun Oct 17 2021

.SYNOPSIS...
A strong cold front moves offshore overnight with showers
exiting the region from west to east. Mainly dry and cool 
weather follows Sunday into early next week. Milder temperatures
return by mid to late next week before cooler temperatures 
follow for next weekend.

&&

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

Still a sliver of MUCAPES up to 500 J/kg across the 
Cape/Islands where locally heavy showers and isolated t-storms
will lift across the region next hour or so. Brief wind gusts to
40 mph possible with any t-storm. Cold front moving onto the 
Cape and will move offshore around 07z ending the threat of 
thunder. Otherwise, numerous light to moderate showers will move
east across the region. These showers are exiting the CT valley
and will end in BOS-PVD corridor around 09z, and the 
Cape/Islands 10-12z. Partial clearing will develop from west to 
east after the showers move out. 

Much cooler/drier air will be working in from the northwest 
behind the cold front. Low temps by daybreak may drop into the 
upper 40s in the Berkshires and northern Worcester Hills, with 
low to mid 50s elsewhere, except upper 50s Cape/Islands.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
Sunday

Will see clearing skies early tomorrow in the wake of the
passing cold front. However as a cold pool aloft settles 
overhead we'll see the development of some diurnal cu during the
afternoon as well a spot instability shower or two. High 
temperatures will be much cooler than we saw last week with 
highs topping out in the 60s for much of southern New England. 
Gusty west/northwest winds will gradually diminish through the 
day as the pressure gradient relaxes. 

Sunday Night

Persistent 10 mph winds out of the west/northwest will limit 
radiational cooling tomorrow night. However we'll still see some
pretty chilly overnight low temperatures across the interior in
the low- mid 40s. Areas near the coast stay a bit warmer 
bottoming out in the upper 40s to perhaps 50 degrees. Otherwise,
a very quiet Sunday night.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Highlights...

* Mainly dry and cool Mon into Tue
* Milder Wed & especially Thu with 70+ highs possible
* A few showers possible sometime Thu night and/or Fri
* Turning cooler next weekend and watching an offshore wave 

Details...

Monday and Tuesday...

Deep trough with cold pool aloft overhead will result in a cool
start to the work week. We should see an abundance of diurnal 
clouds on Monday, but given limited moisture nothing more than a
brief spot shower or two. Otherwise, rather cool and a bit 
breezy with high temperatures only in the middle 50s to the 
lower 60s. Low temps Monday night should be well down into the
40s for many locales and probably 30s for some outlying 
locations. Upper trough lifts further northeast by Tuesday, so 
expect to see more in the way of sunshine which should allow 
temps to recover into the lower to middle 60s in many locales.

Wednesday and Thursday...

High pressure moves off the southeast coast as another frontal
system approaches from the west by Thu. This will allow for a 
return southwesterly flow of milder air back into the region. 
Depending on timing and the amount of solar insolation expect 
to see highs recover into the 60s to near 70 on Wed. In fact, 
850T between +10C and +12C by Thu should support highs of 70+ 
for many locales as long as enough sunshine is realized. Dry 
weather should prevail Wed and through most of the daylight 
hours on Thu as the deeper forcing/moisture will remain to our 
west. 

Thursday night into Next Weekend...

A few showers are possible sometime Thu night and/or Friday with
the next frontal system, but it does not look like a washout
with limited moisture & forcing. Otherwise, perhaps another 
mild day Friday before things trend cooler by next weekend. The 
magnitude of cooling next weekend remains uncertain with the 
GEFS quickest/coolest; while the EPS is slowest and mildest. The
GGEM Ensembles seem to be in between. However, all guidance has
a northeast trough developing so expect cooler temps that will
be near or below normal. We also will have to watch a wave of 
low pressure off the coast for a period of unsettled weather, 
but that remains to be seen if it ends up close enough for some 
rain.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Low - less than 30 percent. 
Moderate - 30 to 60 percent. 
High - greater than 60 percent.

06Z TAF Update: 

Through 12z...
Locally heavy showers and isold thunder threat for the
Cape/islands will end around 07z as winds shift to W/NW behind
the cold front. Otherwise, numerous showers with areas of 
MVFR, but conditions improving to VFR with showers ending from 
west to east 06-12z. 

Today...High confidence. 
VFR with broken cigs 5-6k ft developing in the afternoon. A 
spot shower possible. W/NW wind gusts to 20 kt. 

Tonight...High confidence. VFR. W/NW wind 5-15 kt. 

Monday...High confidence. 
VFR with broken cigs 5-6k ft developing. Spot shower possible. 
NW gusts to 20 kt.

KBOS Terminal...High confidence in trends.

KBDL Terminal...High confidence in trends.

Outlook /Monday Night through Thursday/...

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

Tuesday through Tuesday Night: VFR. Windy with local gusts up
to 30 kt. 

Wednesday through Thursday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels.

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

Marine

Tonight

Gusty south/southwest winds of 25+ knots continue into the early
evening hours ahead of a passing cold front. Showers and 
possible a few thunderstorms will be possible as this front 
moves over the coastal waters overnight. Winds shift to the 
west/northwest behind the front prior to sunrise.

Tomorrow

Winds come down to the 15-25 knot range behind the cold front
during the day tomorrow. Seas come down below 5 feet for the 
outer waters.

Tomorrow night

Winds pick back up to 25 knots as a low-level jet moves over the 
southern Waters. This will result in seas rising to 5 feet for 
the outer marine zones. This may warrant SCY tomorrow night and 
into early Monday. 

Outlook /Monday Night through Thursday/...

Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft. Slight chance of rain
showers. 

Monday Night: Moderate risk for Small Craft Advisory winds with
local gusts up to 30 kt. Areas of seas approaching 5 ft. Slight
chance of rain showers. 

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of seas approaching 5 ft. 

Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Local rough seas. 

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Areas of seas approaching 5 ft. 

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

Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas locally approaching 5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 4 AM EDT early this morning for 
     ANZ232>235-237.
     Small Craft Advisory until 2 AM EDT early this morning for 
     ANZ230-231-236-251.
     Small Craft Advisory until 2 PM EDT this afternoon for ANZ250-
     254>256.

&&

$$
SYNOPSIS...Frank/RM
NEAR TERM...KJC
SHORT TERM...RM
LONG TERM...Frank
AVIATION...KJC/Frank
MARINE...Frank/RM
      

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