Lexington Weather

Lexington, Massachusetts, USA

9/22/2021 12:47pm 
  • Lexington Conditions: Overcast
  • Temperature: 75.2°F / 24.0°CWarmer 0.5°F than last hour.
  • Dew Point: 68.2°FDecreased 0.5°Fsince last hour.
  • Relative Humidity: 79%Decreased 3.0% since last hour.
  • Wind: Wind from SSW SSW 5 mph, 10-min avg: 3 mph, gust: 12 mph
  • Barometer: 30.11 inFalling 0.02  inHg/hr Falling Slowly
  • Visibility: 10 miles
  • Rain Today: 0.00 in

Area Forecast Discussion
for Boston, MA

FXUS61 KBOX 190558

Area Forecast Discussion
National Weather Service Boston/Norton MA
158 AM EDT Sun Sep 19 2021

A cold front will move across the region during the predawn
hours Sunday and be accompanied by a few showers or 
thunderstorms over eastern MA. High pressure builds later  
Sunday morning and will bring sunny and dry conditions from 
through mid week. An approaching cold front will be accompanied
by showers and possible thunderstorms sometime Thursday into 
Friday, followed by dry and seasonably mild conditions Saturday.



2 AM update...

Short wave trough and cold front moving thru eastern MA early
this morning and accompanied by scattered showers and possibly
an isolated thunderstorms. True post frontal airmass now
advecting into western MA and southwest NH with dew pts in the
50s. This airmass will reach the coastline by sunrise or shortly
thereafter. Mostly cloudy over eastern MA, with partial clearing
westward into RI/CT and western-central MA. This clearing trend
reaches the coastline toward daybreak. 



Sunday looks to be the start of several gorgeous late summer 
days. With high pressure building in, skies should be sunny. 
Highs will be in the 70s with pleasantly dry dewpoints in the 
upper 40s to low 50s. 

With high pressure moving overhead, conditions will be ripe for
excellent radiational cooling. Leaned heavily on MOS guidance to
derive overnight lows in the mid 40s to low 50s, except for mid
50s in the urban centers and immediate coast. Might be a good
idea to close the windows! 

In addition, have opted to hoist Rip Current Statements for the
entire eastern MA coast through tomorrow evening due to
remaining swells and lingering elevated rip current risks from 
Tropical cyclone Odette.




* Pleasant, dry stretch of weather Mon into Wed with seasonably mild 
  day and cool nights

* Showers & scattered T-storms Thu into Fri


Strong mid level ridge along the east coast into New Eng early next 
week moves slowly east Wed/Thu as a high amplitude trough moves into 
Gt Lakes with cut off low developing. GFS remains most progressive 
of the guidance envelope sweeping the trough and attending cold 
front through on Thu while ECMWF/GGEM have a much slower evolution 
with fropa not until Fri/Fri night. Given the GFS progressive bias 
in amplified patterns we will trend the forecast toward the slower 
ECMWF solution and its ensembles which favor mainly dry weather into 
Wed, then increasing risk of wet weather with showers and possible t-
storms Thu into Fri. Additionally, with ECMWF indicating upper low 
opening up and lifting well to the NW into eastern Canada, airmass 
behind the fropa will be modified so not expecting a significant 
cooling trend into next weekend.


Strong high pres will maintain dry weather Mon and Tue and possibly 
into Wed as well. By Wed, the surface high will be well east of New 
Eng with increasingly moist southerly flow possibly bringing a few 
light showers in the west. However, much of the area should remain 
dry. Forecast confidence decreases beyond Wed due to timing 
differences on upstream trough and approaching cold front. ECMWF 
ensembles also vary a bit on timing so we will have chance showers 
Thu into Fri although there is uncertainty regarding which time 
period will have the greatest risk of showers. Pre-frontal PWAT 
plume approaching 2 inches suggests some heavy rainfall is possible 
with the front. Drying trend expected by Sat. 


Despite strong mid level ridge, high pres from Maritimes with 
ridging extending into New Eng will result in seasonably mild days 
Mon into Wed with highs low/mid 70s. Cool nights Mon night and Tue 
night. Still mild and somewhat humid Thu ahead of the front and 
depending on timing of fropa, the mild weather could linger into 
Fri, especially eastern New Eng where highs could reach into the 
70s. Not much push of cool air in the post frontal airmass on Sat 
with 850 mb ensemble mean temps around 10C so highs should reach the 
70s again.


Forecaster Confidence Levels.

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

06z Update...


MVFR/IFR across eastern MA along with scattered showers,
improves to VFR 09z-12z along with dry weather. Elsewhere,
mainly VFR and dry weather. NNW winds becoming NNE around
daybreak and increasing 15-20kt along the eastern MA coast.
Elsewhere 5-15 kt. 

Tonight...VFR. Winds light and variable. 

Monday...VFR with light and variable winds, becoming onshore
along the coast. 

KBOS Terminal...high confidence, dry weather toward 09z and then
MVFR improving to VFR by 16z. Then an extended stretch of dry
weather, VFR, light/variable winds with afternoon seabreezes. 

KBDL Terminal...High confidence.

Outlook /Monday night through Thursday/

Monday night through Tuesday Night: VFR. 

Wednesday: Mainly VFR, with local MVFR possible. 

Wednesday Night: Mainly MVFR, with local IFR possible. Slight
chance SHRA.

Thursday: Mainly MVFR, with local IFR possible. Breezy. Chance


Forecaster Confidence Levels.

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

Generally high confidence in the forecast. Even as Tropical 
cyclone Odette continues to pull further away into the Atlantic 
Ocean, lingering swells and 4-7 ft seas warrants the
continuation of Small Craft Advisories for most outer waters
through a good part of Sunday.

Chance of a shower or thunderstorm this evening. Areas of dense
fog over the waters east of Massachusetts overnight tonight, 
reducing visibility to less than 1 nm at times.

High pressure moves overhead late Sunday, resulting in light and
variable winds and seas falling below 5 ft overnight Sunday. 

Outlook /Monday Night through Thursday/...

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

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

Wednesday: Winds less than 25 kt. Seas up to 5 ft. 

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

Thursday: Winds less than 25 kt. Areas of rough seas. Chance of
rain showers.


MA...High Rip Current Risk through this evening for MAZ007-019-022-
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ250-
     Small Craft Advisory until 2 PM EDT this afternoon for ANZ255-


NEAR TERM...Nocera

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