Lexington Weather

Lexington, Massachusetts, USA

87°F
8/8/2022 6:48pm 
  • Lexington Conditions: Clear
  • Temperature: 86.9°F / 30.5°CColder 2.5°F than last hour.
  • Dew Point: 73.8°FDecreased 0.3°Fsince last hour.
  • Relative Humidity: 65%Increased 4.0% since last hour.
  • Wind: Wind from W W 6 mph, 10-min avg: 2 mph, gust: 14 mph
  • Barometer: 29.80 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 042345
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
745 PM EDT Thu Aug 4 2022

.SYNOPSIS...
Heat and humidity will be the main weather story right into 
early next week. The hot stretch continues Friday with even
higher humidity. The greatest potential for showers and 
thunderstorms will be Friday into Saturday, with localized heavy
rainfall possible at times. It may be Tuesday or later before 
this heat and oppressive humidity finally breaks in a 
significant way.

&&

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

740 PM UPDATE...

Forecast remains largely on track. A new daily max temperature
record of 98F was set at Boston while 96F was enough to tie for
Hartford. A few strong to severe thunderstorms have mostly
missed our CWA to the north and west. Besides the negligible
shear to sustain updrafts, SPC mesoanalysis shows a steep K
index gradient northwest of our area. So while places like
Bennington received reports of localized damaging wind gusts 
and the Albany area reported up to 3 inches of rain, there was
simply too much dry air aloft to deal with to even organize
updrafts. The only exception was across far northwest Franklin
county where part of a decaying thunderstorm spilled over the 
Berkshires but nothing severe. Otherwise, a quiet night of
weather with muggy and uncomfortable conditions. The marine
layer or fog bank that has been draped over Nantucket the whole
day would move slightly north overnight, possibly resulting in
reduced visibility across the south coast into Cape Cod. 


PREVIOUS DISCUSSION...

Well, it's hot out. Boston is sitting two degrees above the record 
for the day, at 98F. Importantly, the "feels like" temperature (heat 
index) has risen to 100 and above for many locations across southern 
New England. As the heat increases instability has risen with it; 
SPC mesoanalysis shows surface based CAPE values increasing to 1,500-
2,000 J/kg. Shear is extremely weak to nil, however, so while 
scattered showers and thunderstorms are possible in northwest MA 
this afternoon/evening they should be of the garden variety (non-
severe). The showers and thunderstorms come to an end in the hours 
just after sunset with loss of daytime heating leaving a quiet night 
with a mix of mid/high clouds to the northwest and low stratus and 
fog over southeast MA thanks to that increased low level
moisture.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
We end the week with more of the same: heat and humidity. The 
humidity, though, will be markedly higher tomorrow as dewpoints 
surge into the mid 70s on SW flow. Thus, while actual temperatures 
should be a few degrees cooler, the heat index will once again reach 
over 100 F. The bullseye of highest heat index Friday will be over 
southeast MA rather than northeast MA thanks to the higher 
dewpoints. All that to say, another day of dangerous heat is in 
store, so take the proper precautions ahead of time to limit your 
time outside. Heat Advisories continue for all of southern New 
England. 

Showers and thunderstorms will be more likely on Friday thanks to 
some better forcing from an approaching cool front and weak mid 
level shortwave. As it moves in it will take advantage of strong 
instability (CAPE 1000-1500 J/kg) and deep moisture (PWATs ~2 
inches) initiate a round of showers and thunderstorms generally 
between noon and 8 PM. Like today, the thinking is that these will 
be sub-severe owing to the non-existent bulk shear for organizing 
and sustaining convection. Given the instability and steep low level 
lapse rates, though, can't rule out some localized damaging winds. 
More likely would be the an isolated threat of some urban and poor 
drainage flooding given weak steering flow and deep moisture. 
Showers and storms come to an end after sunset but with the stalled 
front draped across northern areas this may be enough to kick off 
some scattered showers overnight. Lows will be very warm, in the 70s.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Highlights...

* Oppressive heat and humidity continues through early next week. 
  There is the chance for isolated showers and thunderstorms daily. 
* A slow-moving cold front could bring much needed rainfall to 
  portions of the region by later next week, but timing and areal 
  coverage remain uncertain at this time. 
  
Details...

Saturday into Sunday...

Bermuda High continues to hold strong this weekend and support a 
deep southwest flow pattern into southern New England. As a result, 
above normal temperatures and humid conditions will persist. Whether 
individual locations meet the criteria for a heatwave, which is 
three consecutive days of 90 deg, the combination of air temperature 
and dew points in the mid 60s to mid 70s will yield heat indices in 
the mid 90s to low 100s. The elevated dew points also means muggy 
and uncomfortable nights. Current heat headlines will likely be 
extended with future forecast packages for this weekend, and perhaps 
into Cape Cod and the Islands. 

Precipitation wise, weak upper level short wave will bring some 
cloudiness and a chance for isolated showers and thunderstorms. 
While there will be sufficient instability for convection, little to 
no deep-layer shear will suppress severe thunderstorm development. 
However, abundant deep layer moisture and weak boundary layer winds 
could support slower moving thunderstorms with localized, brief 
heavy downpours. Unfortunately, short of widespread soaking 
rainfall, there will barely put a dent in the deteriorating drought 
situation, where the eastern half of our CWA is now in D2 severe 
drought category according to the US Drought Monitor. 

Monday into Thursday...

No notable air mass change as we enter the new work week so high 
heat and humidity continues with a trend towards somewhat more 
seasonable temps later in the work week. For reference, typical 
highs for the second week of August are in the low to mid 80s. For 
those tired of the heat and humidity, we may get a reprieve sometime 
in the mid to late week time frame. But there remains plenty of 
uncertainty with regards to the timing. CIPS analog indicates that 
there is a somewhat better chance for stronger thunderstorms in the 
Tuesday or Wednesday time frame, but that is contingent on the 
strength and progression of the cold front. Given the plenty of 
uncertainty, mainly stuck to blended guidance for this part of the 
forecast.  While there may seem to be no end in sight to this heat, 
the good news is that we are now past the climatologically warmest 
time of the year and cooler days are not far away.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels:

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

Tonight...Moderate confidence. 

Generally VFR except for localized IFR to LIFR for Cape
terminals due to fog development. 

Friday...Moderate confidence.

Areas of LIFR to start the day. Sea breeze expected to kick in
for BOS around 15-17z time frame. Generally VFR. Greater risk 
for showers and thunderstorms, especially across the western
two-thirds of southern New England.

Friday night...Moderate confidence. 

Mainly VFR. MVFR/IFR CIGS possible for some, mainly along the
south coast, Cape, and islands. SHRA and TSRA come to an end
after sundown. 

KBOS...High confidence in TAF. 

KBDL...High confidence in TAF. 

Outlook /Saturday through Tuesday/...

Saturday: Mainly VFR, with areas MVFR possible. Breezy. Chance
SHRA, isolated TSRA.

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

Sunday: Mainly VFR, with areas MVFR possible. Breezy. Chance
SHRA, isolated TSRA.

Sunday Night: Mainly VFR, with local MVFR possible. Breezy. 

Monday: Mainly MVFR, with areas VFR possible. Breezy. Chance
SHRA.

Monday Night: Mainly MVFR, with local IFR possible. Breezy.
Chance SHRA.

Tuesday: Mainly MVFR, with areas VFR possible. Breezy. Chance
SHRA, isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

High confidence. 

Winds and seas to remain relatively tranquil through Friday
night.

Areas of fog tonight into Friday morning for southeast MA
including Cape Cod and the islands. Fog should dissipate during
Friday morning.

Outlook /Saturday through Tuesday/... 

Saturday: Winds less than 25 kt. 

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

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

Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers. 

Monday Night through Tuesday: Winds less than 25 kt. Seas up to
5 ft. Chance of rain showers, isolated thunderstorms.

&&

.CLIMATE...
August 4th daily record maximum high temperatures...

BOS - 96F [1928]
ORH - 95F [1944]
PVD - 98F [1944]
BDL - 96F [1944]

August 4th daily record maximum low temperatures...

BOS - 76F [1930] 
ORH - 72F [2002] 
PVD - 74F [2010] 
BDL - 74F [2006]

August 5th daily record maximum high temperatures...

BOS - 100F [1955]
ORH - 96F  [1944]
PVD - 100F [1944]
BDL - 101F [1955]

August 5th daily record maximum low temperatures...

BOS - 76F [1938]
ORH - 73F [1938]
PVD - 77F [1938]
BDL - 76F [1938]

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Air Quality Alert until 11 PM EDT this evening for CTZ002.
     Heat Advisory until 8 PM EDT Friday for CTZ002>004.
MA...Air Quality Alert until 11 PM EDT this evening for MAZ005>007-
     010>012-014.
     Heat Advisory until 8 PM EDT Friday for MAZ002>021-026.
RI...Heat Advisory until 8 PM EDT Friday for RIZ001>007.
MARINE...None.

&&

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

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