Lexington Weather

Lexington, Massachusetts, USA

10/17/2021 10:14pm 
  • Lexington Conditions: Clear
  • Temperature: 51.6°F / 10.9°CColder 1.1°F than last hour.
  • Dew Point: 46.9°FDecreased 0.4°Fsince last hour.
  • Relative Humidity: 84%Increased 2.0% since last hour.
  • Wind: Calm, 10-min avg: Calm, gust: 4 mph
  • Barometer: 29.68 in Steady
  • Visibility: 10 miles
  • Rain Today: 0.35 in

Area Forecast Discussion
for Boston, MA

FXUS61 KBOX 120152

Area Forecast Discussion
National Weather Service Boston/Norton MA
952 PM EDT Mon Oct 11 2021

High pressure remains in control through late this week with 
above normal temperatures. Widespread precipitation chances 
return to the forecast for sometime Saturday into Sunday, but 
timing is uncertain at this time.


950 PM update...

Area of stratus has developed across portions of SE MA and this
moisture is expected to expand across much of eastern MA and RI 
overnight with widespread stratus. The extent of fog is more
uncertain but we do expect areas of fog to develop in eastern
MA and portions of CT valley. Locally dense fog is possible but
not confident in widespread dense fog. Will continue to monitor
latest trends. 

Previous discussion...

Latest near term guidance has been consistent with developing a
stratus layer across most of the eastern half of southern New 
England late this evening, and especially after midnight.
Surface observations, and now derived satellite products have
also been hinting at a shallow moist layer just below 1000 ft 
or so. Given all these factors, confidence is increasing in this
outcome. Main change to the forecast this evening was to 
increase clouds for some areas overnight.

A trickier proposition will be if also fog develops, and how
widespread it will become. Thinking right now that the usual 
low spots are likely to see some fog. One of the tip offs is not
yet present, and that would be fog along coastal NH and ME. 
Satellite is hinting of this fog over Georges Bank, but no 
supporting evidence to back it up. Given the light onshore flow 
probably becoming light and variable overnight, decided to add 
patchy fog to the forecast, most of which will be after 
midnight. Will hold off on a Dense Fog Advisory until it becomes
more certain that it would be needed.



High pressure continues overhead Tuesday and Tuesday night. 


With the high overhead, expect sea breezes to develop Tuesday,
then light variable wind Tuesday night. On Tuesday expect the
moist surface layer to dry out faster than it did today, leading 
to clearing in the morning and some developing diurnal clouds. 
The mixed layer reaches to 950-mb, possibly a little higher. 
Temperatures at that layer will be equiv to 7C and supporting 
max temps of upper 60s and lower 70s.

Light wind Tuesday night, possibly some trend from the south. 
Another night of fair weather and areas of fog.



* Above normal temperatures with quiet weather through much of
  this week. Cannot rule out a few isolated showers across the
  interior on Wednesday, but the next opportunity for widespread
  rain showers looks to be this weekend. 

Wednesday through Friday...

expecting a mid level ridge to linger over most of the Eastern
Seaboard during this time. High pressure at the surface over the
central Appalachians into the southeast USA. This pattern favors
drier and warmer weather across southern New England. However,
our region will be on the northern edge of this high pressure.
It is possible that a weak surface trough may be enough to
trigger a few showers as it swings by Wednesday into Wednesday
night. The main limitation at this point is having enough 
moisture to generate those showers. Kept the forecast dry during
this time, for now. Looking at above normal temperatures.

Saturday through Monday...

Still appears that this ridging moves offshore towards this
weekend, opening the door for a mid level trough and surface
cold front to move through sometime Saturday into Sunday. This
looks to be our next greatest chance for precipitation. 

 Ridge axis builds offshore and a trough lifts in 
from the Mississippi River Valley on Saturday or Sunday. A deep 
low should be situated to the northwest of the region, which 
will slide a warm and cold front through New England. This far 
out timing and intensity is uncertain due to model differences, 
but this brings a shot for more widespread precipitation. 
Turning colder towards early next week behind this cold front,
but still near normal for mid October.


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


VFR early. Fog and low clouds developing overnight with cigs
below 1000 feet. Vsbys generally 4-5 miles overnight and locally 
below 1 mile.


Fog and low clouds burn off. Early to mid morning IFR returns to
VFR mid to late morning and afternoon. Light variable wind may
become light southeast during the day.

Tuesday night...

Winds again become light. Areas of fog/low clouds again form
with ceilings below 1000 feet overnight and vsbys locally below
1 mile.

KBOS Terminal...High confidence in TAF. 

KBDL Terminal...High confidence in TAF.

Outlook /Wednesday through Saturday/...

Wednesday through Friday: VFR. 

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

Saturday: Mainly MVFR, with local VFR possible. Breezy. Chance


Forecaster Confidence Levels.

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

Wind will diminish and become variable tonight through Tuesday night 
as high pressure builds fair weather over the waters. Areas of fog 
will form each night with vsbys under 1 mile in spots.  Expect winds 
and seas at Small Craft levels on the southern outer waters tonight 
and Tuesday morning, then below criteria Tuesday afternoon and night.

Outlook /Wednesday through Saturday/...

Wednesday through Friday: Winds less than 25 kt. 

Friday Night: Winds less than 25 kt. Slight chance of rain

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


MARINE...Small Craft Advisory until 10 AM EDT Tuesday for ANZ235-237-
     Small Craft Advisory until 6 PM EDT Tuesday for ANZ254.
     Small Craft Advisory until midnight EDT Tuesday night for 



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