Lexington Weather

Lexington, Massachusetts, USA

8/17/2022 5:53pm 
  • Lexington Conditions: Overcast
  • Temperature: 70.2°F / 21.2°CColder 0.5°F than last hour.
  • Dew Point: 59.2°FIncreased 1.6°Fsince last hour.
  • Relative Humidity: 68%Increased 5.0% since last hour.
  • Wind: Calm, 10-min avg: Calm, gust: 1 mph
  • Barometer: 29.86 inFalling 0.02  inHg/hr Falling Slowly
  • Visibility: 10 miles
  • Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

FXUS61 KBOX 140232

Area Forecast Discussion
National Weather Service Boston/Norton MA
1032 PM EDT Sat Aug 13 2022

High pressure provides dry and cool weather tonight, followed by
a warmer afternoon Sunday, however humidity will remain very
comfortable. High pressure and dry weather likely lingers into
Monday, however nearby low pressure likely results in cooler
than normal temperatures Tuesday thru Thursday, along with the
chance of rain from time to time. Then trending warmer and 
somewhat more humid Friday into next weekend.



1030 PM update...

Quiet evening as Nighttime Microphysics satellite imagery shows
cloud cover decreasing with the loss of diurnal heating. With
calm to light winds near the surface, it will be a cool and
refreshing night to open the windows! No significant changes
made to the forecast.

Previous Discussion...

* Cool night ahead

1020 mb high over the eastern Great Lakes advects east into New
England tonight, providing dry and cool conditions. Diurnal 
strato-cu will erode with sunset, and the combination of 
diminishing winds and dew pts in the 40s and 50s, will provide 
ideal radiational cooling conditions. Thus, followed the cooler 
MOS guidance to derive overnight mins, which yields widespread 
50s across the region. The coolest areas will be in the I495 
corridor of eastern MA and also in western MA, where temps will
dip into the upper 40s! Not quite as cool in the urban areas,
with lows in the upper 50s to lower 60s. Nonetheless, a taste 
of early fall weather.


330 PM update...

* More sunshine & warmer Sunday but humidity remaining 


A cool start to the day, but with upper trough and cold pool 
aloft exiting into Maine and New Brunswick, short wave ridging
will yield warmer temps and less diurnal clouds across MA/RI/CT
Sunday. 850 mb and 925 mb warm to about +12C and +19C
respectively, combined with mixing above 850 mb and still very 
dry soils, supports highs 80-85, upper 70s high terrain and 
along the immediate coast, where seabreezes will occur. Despite 
warmer temps, humidity levels will remain very comfortable, with
dew pts in the 40s and 50s. Overall, spectacular weather for 
mid August, enjoy! 

Sunday night...

Weak high pressure provides light winds, dry weather, mostly 
clear conditions, hence another cool night but not as cool as
Sat night. Followed a blend of all MOS guidance to derive
overnight mins, which translates to lows in the 50s, except low
60s in the urban areas. Another very pleasant, dry night.


330 PM update...


* Periodically unsettled weather expected for the first through the 
  middle of the work week, with the best chance for appreciable 
  rainfall being Tuesday night into Wednesday

* High temperatures hover around normal or just below normal in the 
  upper 70s/low 80s through Thursday before we switch to a warmer 
  and more humid pattern Friday into the weekend. Even so, 
  oppressive heat and humidity the likes of which we saw last 
  week are not expected. 


Monday through Thursday...

Much of the next week will feature a perpetually reloading mid level 
trough over the east coast with persistent ridging over the western 
U.S. For southern New England this means a prolonged reprieve from 
the oppressive heat and humidity of late thanks to cooler than 
average temperatures beneath this trough. 850 mb temperatures of 9-
11C together with north/northeast flow around a surface disturbance 
will hold temperatures to a seasonable upper 70s/low 80s each day. 

The more challenging forecast is that of precipitation (or lack 
thereof). While this pattern is much more favorable to widespread 
precipitation than what we've been in recently, guidance isn't as 
bullish on widespread precipitation as it was looking a few days 
ago. There would appear to be two camps among the global guidance, 
with the GFS all in on the low pressure system in question (moving 
off the coast of the mid-Atlantic early Tuesday) approaching and 
then moving directly overhead on Wednesday, while the ECMWF keeps 
high pressure strong enough to shunt the low further east and 
offshore keeping the bulk of the rain away. For what it's worth, 
ensemble trends have been downward for the percentage chance of >0.5 
inches of rain and the 12Z GFS is a westward outlier of all the 
members in the GEFS ensemble. It will be interesting to see what the 
NAM has to say in as the next few runs bring it into the window in 
question. All this to say, while precipitation chances are certainly 
greater Tue-Thu they may be more spotty in nature or even 
essentially a shutout; it's simply too soon to say for sure. For 
now, the best shot at rain will be over eastern MA and RI. 
Regardless, we're looking at a cooler stretch with potential for 
more clouds than sun. 

Friday and Saturday...

Beyond Thursday the trough finally shifts to the east and mid level 
ridging takes hold with SW flow pumping up temps and humidity 
levels. While it will be warmer than most of the week we aren't 
expecting temperatures to the levels that we saw last week; highs in 
the upper 80s are most likely, with negligible rain chances.


Forecaster Confidence Levels:

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

00Z TAF Update...

Thru 12z Monday...VFR cloud bases, dry weather and light winds,
with onshore winds for coastal terminals Sunday afternoon. See 
individual TAFs for details.

KBOS...High confidence in TAF. Afternoon seabreeze again Sunday

KBDL...High confidence.

Outlook /Monday through Thursday/...

Monday: VFR. Slight chance SHRA.

Monday Night: VFR. 

Tuesday: VFR. Breezy. Slight chance SHRA.

Tuesday Night: VFR. Breezy. Chance SHRA.

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


Forecaster Confidence Levels:

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

330 PM update...

1020 mb high pressure over the eastern Great Lakes advects into
southern New England tonight/Sunday and then drifts just
offshore Sunday night. This results in dry weather and good vsby
over the coastal waters of MA/RI. Light winds, locally onshore
along the immediate coast.  

Outlook /Monday through Thursday/... 

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

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

Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers. 

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




NEAR TERM...Nocera/Chai

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