Lexington Weather

Lexington, Massachusetts, USA

86°F
8/8/2022 7:14pm 
  • Lexington Conditions: Clear
  • Temperature: 85.8°F / 29.9°CColder 2.2°F than last hour.
  • Dew Point: 73.6°FDecreased 0.2°Fsince last hour.
  • Relative Humidity: 67%Increased 4.0% since last hour.
  • Wind: Wind from SSE SSE 2 mph, 10-min avg: 2 mph, gust: 15 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 071357
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
957 AM EDT Sun Aug 7 2022

.SYNOPSIS...
Heat and humidity will be the main weather story right into 
early next week. Heat Advisories have been extended through
Monday, and the threat of isolated to scattered thunderstorms 
will remain as well. It may be Tuesday, or later, before this 
heat and oppressive humidity finally breaks in a significant 
way. Will have daily shots for showers and thunderstorms for 
much of next week, but no washouts are anticipated at this time.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

10 AM Update: 

No significant change needed to the forecast or key messages for
today, with oppressive heat and humidity again a focus, with
afternoon isolated to widely scattered showers or thunderstorms
dissipating by sundown. 

Remains very muggy this morning with dewpoints generally in the
low to middle 70s again. Other than stratus affecting Cape Cod
and the Islands, mostly clear to partial cloudiness begins
Sunday. Strong heating to push highs into the low-middle 90s,
with upper 80s across the Cape and Islands. Heat Advisories
continue with no changes to its status, with expectation of 95
to 103F heat indices. 

Given the high dewpoints, won't take much heating to develop
cumulus fields with moderate instability and weak wind shear
environmental setup for today. On the mesoscale, looks like a
subtle windshift boundary sets up and could force weak 
convergence along or just north of the Mass Pike per HRRR and 
NAM-3km guidance. May see more in the way of shower/t-storm 
coverage compared to yesterday toward widely scattered near or 
north of the Mass Pike. HRRR has been really consistent in 
showing storms developing near the berkshires by mid-aftn
(19z-ish) and moving eastward through late-afternoon into 
central MA and on into Metrowest. Poor wind fields/weak shear to
make any showers or storms highly pulse in character, with 
lightning and localized brief downpours the main risk versus any
severe risk. 

Previous discussion:

Still no significant changes to the overall pattern today. heat
and humidity continue, along with the risk for some disorganized
showers and thunderstorms later today. The only synoptic feature
that would provide more focus to this convection, a stalled
front, will remain well to our north today. Much like the past
few days, not everyone will see a shower or thunderstorm, but do
not have enough confidence to pin it very precisely. Locations
farther inland and closer to northern New England will have a
greater risk than those farther south and east.

Expecting a little more of pressure gradient today, so no east
coast seabreezes.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Any lingering showers and thunderstorms should diminish quickly
with sunset. Leading to another mostly rain-free night. It will
remain muggy, with yet another round of stratus and patchy fog
towards southeast MA.

No real change in air mass Monday, so no real change to the
forecast either. Continued heat and humidity with a risk for
afternoon showers and thunderstorms. Heat Advisories continue as
posted through Monday.

&&

.LONG TERM /MONDAY NIGHT 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 /14Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels:

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

12z TAF Update; 

Today: 

Generally VFR. MVFR-IFR stratus/mist from overnight near the 
southern coast to dissipate by 15z. Iso to widely sct SHRA/TSRA
by mid afternoon to sundown, mainly along/north of I-90.
Included VCSH at ORH but too low prob to carry mention at either
BDL, BED and BOS. SW winds around 10 kt, gusts 18 to 22 kt.

Today...Moderate Confidence. 

Mainly VFR. IFR stratus more likely to persist towards the 
south coast this morning. Brief periods of MVFR in any showers 
or thunderstorms. SW winds 10-15 kt with gusts up to 25 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.

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 /Monday Night through Thursday/...

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

Tuesday: VFR. Breezy. Chance SHRA, slight chance TSRA.

Tuesday Night: Mainly VFR, with local IFR possible. Chance
SHRA, slight chance TSRA.

Wednesday: MVFR/IFR conditions possible. Chance SHRA, slight
chance TSRA.

Wednesday Night: MVFR/IFR conditions possible. SHRA likely,
chance TSRA.

Thursday: Mainly VFR, with local IFR possible. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Monday...High Confidence.

Light winds and seas with early morning areas of fog with 
reduced visibility. Today 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.

Outlook /Monday Night through Thursday/... 

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

Tuesday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain showers, slight chance of thunderstorms. 

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

Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers, slight chance of thunderstorms. 

Wednesday Night through Thursday: Winds less than 25 kt. Rain
showers likely, chance of 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 6 AM EDT Monday for ANZ231>235-237.
     Small Craft Advisory until 1 AM EDT Monday for ANZ236-250.
     Small Craft Advisory until 2 PM EDT Monday for ANZ254>256.

&&

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

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