Lexington Weather

Lexington, Massachusetts, USA

88°F

8/8/2022 6:17pm

Lexington Conditions: Clear
Temperature: 87.8°F / 31.0°C
Dew Point: 73.6°F
Relative Humidity: 63%
Wind: S 3 mph, 10-min avg: 3 mph, gust: 14 mph
Barometer: 29.79 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Southeast Middlesex County, MA - Heat Advisory
- SEE ALL NEARBY ALERTS -

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 071924
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
324 PM EDT Sun Aug 7 2022

.SYNOPSIS...

Heat and humidity will continue to be the main weather story 
well into next week. Heat Advisories continue through Monday, 
and the threat of isolated to scattered thunderstorms will 
remain as well. It may be Wednesday before this heat and 
oppressive humidity finally break in a significant way. Will 
have daily shots for showers and thunderstorms for much of next 
week, with more widespread rain expected sometime Wednesday into
Thursday. 

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...

Forecast is on track this afternoon, with cumulus bubbling across 
southern New England but only sparse showers so far which continue 
to pulse up and quickly collapse. As we go through the afternoon the 
coverage of showers and storms may increase, mainly along and north 
of the MA pike. Mesoanalysis shows 2000-2500 J/kg of CAPE but with 
no shear and lackluster mid level lapse rates which should keep any 
thunderstorms of the garden-variety. With sunset and loss of diurnal 
heating storms will rapidly diminish in coverage leaving mostly 
clear skies, save for the south coast where low level moisture will 
once again bring the threat of low stratus to the Cape and islands. 
Low temps will be quite warm owing to the very moist airmass, in the 
mid 70s. 

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...

Monday we rinse and repeat, as has been the story for days now. The 
hot and humid airmass remains overhead  with little change to speak 
of. SW winds continue and advect in marginally warmer air in the low 
levels (850 mb temps increase from 18C to 19-20C) so temperatures 
will be a few degrees warmer, especially in the Connecticut Valley. 
Highs in the low to mid 90s and dewpoints in the mid 70s mean 
another day of heat indices at or above 100F. Instability will once 
again be high (CAPE >1500 J/kg) with poor shear (though a bit higher 
than Sunday). Not expecting a severe threat with any storms that pop 
up on Monday afternoon and evening. Any convection that does fire 
will die down after sunset leaving a dry forecast for the overnight 
hours. Increasing winds late in the day and overnight will take the 
edge off, especially along the south coast and offshore. 

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Highlights...

* Slow southward movement to cold frontal boundary will favor 
  increased clouds and a few opportunities for showers and 
  t-storms Tue thru Thurs, with better chances on Wed. 

* Very warm and humid weather continues on Tues but odds for
  more cloud cover could temper oppressive heat. Mostly cloudy 
  conditions Wed and Thurs will bring cooler air temps but still
  quite humid. 

* Much drier/more refreshing air mass Fri into next weekend 
  with prevailing dry weather.

Details:

Precipitation Chances:

The focus in the first couple of days of the long-term forecast
period is a southward-sagging frontal boundary; per ensemble 
means, this feature projects to bring a few opportunities for 
showers and thunderstorms late Tue into Thurs. While it remains 
a heavily convective pattern, which means not everyone will see 
rains like some of the coarser-resolution global and ensemble 
guidance QPF would indicate, the front-parallel mid-level flow 
could favor several rounds of showers or storms, some which 
could feature local downpours given ensemble mean 2 sigma PWAT 
levels around 2". Have indicated at least Chance PoP beginning 
later Tue through Thurs. However a period of Likely was 
introduced for Wednesday based on reasonable consensus in the 
EPS/GEFS/GEPS ensemble means with notable 50-70% probs for 24 
hour rainfall in the 0.5" or greater range. There remains spread
in timing the front's southward progress in the Tue thru Thurs 
timeframe which still carries some degree of uncertainty, but 
seems that the middle portion of the workweek should tend to 
feature more cloud cover and increased chances for welcomed 
rains. Despite some indications in CIPS Analog guidance, 
prospects for severe weather in the Tue thru Thurs timeframe 
appear minimal given weak wind fields and correspondingly low 
shear values. 

By late week into the weekend, guidance favors a return to 
drier weather with continental NW flow and high pressure 
building into interior and western New England.

Temperatures and Humidity Levels: 

Monday night could be one of the warmer and more humid nights 
experienced in this stretch of oppressive heat and humidity with
widespread lows in the mid to even upper 70s south of the Mass 
Pike; some indication for cooler lows mid-upper 60s in NE MA as 
a pressure wedge tries to build down the NH/ME seacoast. Tues 
looks to be the last very warm day in this stretch of heat and 
humidity; given cloud cover trends there's still uncertainty on 
highs here but undercut the warm-biased NBM values by 2-4 
degrees. With dewpoints upper 60s to lower-mid 70s, heat indices
fall shy of Advisory levels in the mid-80s to low 90s. 

Wed and Thurs begin a trend toward cooler/more seasonable 
temperatures but this is due to increasing cloud cover versus 
any appreciable change in air mass, and humidity levels will 
however still be elevated. It won't be until the front clears 
our area for later in the week when a much more refreshing air 
mass then filters into Southern New England, with surface ridge 
and broad longwave troughing develops. Continued seasonable with
comfortable humidity levels into the weekend.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels:

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

18z TAF Update; 

This afternoon...High confidence. 

VFR. Iso to widely sct SHRA/TSRA through 02Z, mainly 
along/north of I-90. SW winds around 10 kt, gusts 18 to 22 kt.

Tonight...Moderate Confidence. 

Mainly VFR. Areas of IFR in stratus expected towards the south 
coast late. Light SW winds.

Monday...Moderate Confidence.

Mainly VFR. IFR stratus more likely to persist towards the 
south coast around daybreak. Brief periods of MVFR in any
afternoon showers or thunderstorms. SW winds 5-10 kt with gusts
up to 20 kt.

Monday night...High confidence. 

VFR. SW winds 5-15 kts gusting to 25 kts for southeast MA. 

KBOS...Moderate confidence in TAF due to uncertainty as to
whether any TSRA makes it to the terminal this afternoon.
Greatest risk, though still low, is no sooner than 20z.

KBDL...Moderate confidence in TAF due to uncertainty as to
whether any TSRA makes it to the terminal this afternoon.
Greatest risk, though still low, is no sooner than 19z. 

Outlook /Tuesday through Thursday/...

Monday Night: VFR. Breezy. Slight chance SHRA, slight chance
TSRA.

Tuesday: VFR. Breezy. Chance SHRA, isolated TSRA.

Tuesday Night: Mainly VFR, with areas IFR possible. Chance
SHRA.

Wednesday: MVFR/IFR conditions possible. Chance SHRA.

Wednesday Night: Mainly VFR, with local IFR possible. SHRA
likely.

Thursday: Mainly VFR, with local MVFR possible. Chance SHRA,
isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Monday night...High Confidence.

This afternoon and tonight, SW winds 15-20 kt with gusts up to 
25 kt. Seas increase to 5-6 ft on the southern waters tonight. 
Winds and seas diminish some into Monday, with rough seas 
lingering across the outer coastal waters the longest. Winds and
seas increase once again Monday evening and overnight. 

Outlook /Tuesday through Thursday/... 

Monday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Slight chance of rain
showers, slight chance of thunderstorms. 

Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas. 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 locally approaching
5 ft. Chance of rain showers. 

Wednesday Night: Winds less than 25 kt. Rain showers likely,
isolated thunderstorms. 

Thursday: Winds less than 25 kt. Chance of rain showers,
isolated thunderstorms. 

&&

.CLIMATE...
Record Maximum Temperatures

August 7th:
BOS  98F  [1924] 
ORH  98F  [1924] 
PVD  95F  [2001] 
BDL  100F [1918]

August 8th:

BOS  96F  [1983]
ORH  94F  [1916]
PVD  95F  [1909]
BDL  98F  [2001]

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT Monday for CTZ002>004.
MA...Heat Advisory until 8 PM EDT Monday for MAZ002>023-026.
RI...Heat Advisory until 8 PM EDT Monday for RIZ001>007.
MARINE...Small Craft Advisory until 8 AM EDT Tuesday for ANZ231>235-237.
     Small Craft Advisory until 1 AM EDT Monday for ANZ236-250.
     Small Craft Advisory until 8 PM EDT Tuesday for ANZ254>256.

&&

$$
SYNOPSIS...BW
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...Loconto
AVIATION...Loconto/BW
MARINE...Loconto/BW
CLIMATE...