Lexington Weather

Lexington, Massachusetts, USA

86°F
8/8/2022 7:10pm 
  • Lexington Conditions: Clear
  • Temperature: 86.0°F / 30.0°CColder 2.2°F than last hour.
  • Dew Point: 73.8°FDecreased 0.1°Fsince last hour.
  • Relative Humidity: 67%Increased 4.0% since last hour.
  • Wind: Wind from SW SW Calm, 10-min avg: 2 mph, gust: 12 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 041723
AFDBOX

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

.SYNOPSIS...
Heat and humidity will be the main weather story right into 
early next week. The heat and humidity will peak today and
Friday, with near record high temperatures today as well. The 
greatest potential for showers and thunderstorms will be Friday 
into Saturday, with localized heavy rainfall possible at times.
It may be Tuesday before this heat and oppressive humidity
finally breaks in a significant way.

&&

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

1 PM Update

Well, it's hot out. Boston is sitting just a degree below the
record for the day, at 95F, with several hours of peak heating
yet to come. Importantly, the "feels like" temperature (heat
index) has risen to 100 or 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,
however, so while scattered showers and thunderstorms are
possible in northwest MA this afternoon/evening they should be
of the garden variety (non-severe). 

Previous Discussion...

GOES night fog channel still showing a fair bit of patchy fog
and low stratus across the south coast, Cape, and Islands.
However it appears that it has been starting to become less
widespread over the last hour or so. Short-term models suggest
fog and low stratus lifting over the next couple of hours after
sunset. Have maintained patchy fog through about 14Z. Otherwise,
previous forecast remains on track and no major changes have
been made.

3 AM Discussion

Late night stratus and fog was readily apparent on 
the GOES east fog product. So far, this as constrained to be 
across portions of the outer Cape and Nantucket, with a smaller 
area just getting started across the Connecticut River valley. 
These areas should dissipate shortly after sunrise.

Then the story becomes mostly about heat and humidity. With
essentially full sunshine and near oppressive humidity,
expecting heat index values to each 90 degrees by mid to late
morning, and be near 100 degrees in many place for most of this
afternoon. As such, Heat Advisories continue as posted. A few
areas still have a chance to meet or briefly eclipse Excessive 
Heat Warning levels, mainly in the Hartford-Springfield portion
of the CT Valley and in the Merrimack Valley, but confidence
remains too low for a large enough area to consider upgrading.

So the message remains the same when it comes to the heat. We  
encourage everyone to practice appropriate heat-related
precautions such as staying hydrated, taking frequent breaks 
in air conditioned rooms, and making sure pets and children are
not left alone in cars for any length of time.

As for shower and thunderstorms chances today, the greatest
chance will be across western MA. Despite the heat and 
humidity, it appears there will just be too much dry air towards
the mid levels. The synoptic forcing is also not the greatest, 
with a weak pre-frontal trough. Timing will be everything. At 
this time, expecting showers and thunderstorms to arrive a 
little before sunset, which will limit the chances. Expecting 
any storms to weaken after sunset.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Any isolated garden-variety thunderstorms across western MA and
western CT should weaken and fizzle shortly after sundown. A 
warm and muggy night is in store with continued southerly flow.
Re-developing fog and stratus seems likely as well near south 
coastal New England given the rising dewpoints. Other than the 
higher terrain where upper 60s are forecast, lows should only 
drop into the lower to mid 70s.

Friday will be more favorable for showers and thunderstorms as a
weak cold front and mid level shortwave approaches of region.
This front may linger near the Route 2 corridor by late evening.
Temperatures are expected to be slightly less, due to more 
cloud cover, but dew points should be even higher to compensate.
Thus, Heat Advisories will continue.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Highlights

* Oppressive heat and humidity continues into the weekend. 
  Additional heat headlines will likely be needed.

* Chance for scattered showers and thunderstorms on Saturday
  with the potential for localized heavy rainfall.

* Hot/humid weather continues into early next week before 
  temperatures moderate by middle of next week.

Saturday

Bermuda High holds strong this weekend and continues to support
a deep southwest flow pattern into southern New England. This 
will continue to result in above normal temperatures and
humidity. Additional heat headlines, or perhaps an extension 
of current heat headlines may be needed in some locations. Heat 
indices expected to range in the 95-100 degree range or perhaps 
higher on Saturday and Sunday. 

Saturday will be a bit unsettled as a 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 heavy rainfall. This will 
provide a chance for some isolated areas to receive some much 
needed rainfall. Unfortunately this wouldn't be enough to even 
put a dent in the current precipitation deficits and ongoing 
drought conditions. Temperatures on Saturday "only" expected to 
break into the upper 80s and low 90s, but dewpoints in the low 
to mid 70s will continue to support heat indices well over 95 on
Saturday afternoon. 

Drier low-level air filters in behind the upper-level short-
wave on Sunday. Drier air will support less cloud cover and more
solar radiation. Thus we can expect Sunday to be the warmest of
the two days this weekend with air temperatures getting into 
the low to mid 90s. Deep mixing of drier air to the surface will
support lower dewpoints in the upper 60s to low 70s. This will 
translate to heat indices from 95 to 100 on Sunday afternoon.

Monday through Wednesday

Consensus among model guidance has been for the deep southwest 
flow pattern and hot/humid conditions to continue into at least 
Monday. By early to mid next week, there are signals for a 
trough to settle over the eastern CONUS. This would help bring 
temperatures back down closer to normal. Additionally, model 
guidance has suggested a frontal passage with the associated 
trough that would support showers and thunderstorms sometime in 
the Tuesday to Wednesday time frame. Confidence in timing of the
front and associated trough are low at this time.

&&

.AVIATION /17Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels:

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

This afternoon...High confidence. 

VFR save for ACK where fog and low stratus and looking more
likely to hold on throughout the day. Low prob of isolated TSRA
across far western New England/Berkshires after 22Z. SW winds 
8-13 kt with gusts to 18-20 kt. 

Tonight...Moderate confidence. 

Generally VFR. Stratus and fog likely return to the South 
Coast, Cape and Islands.

Friday...Moderate confidence.

Areas of LIFR to start the day. Generally VFR. Greater risk for
showers and thunderstorms, especially across the western 2/3 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 /Friday Night through Monday/...

Friday Night: VFR. Slight chance SHRA, isolated TSRA.

Saturday: VFR. Breezy. Slight chance SHRA, isolated TSRA.

Saturday Night through Sunday Night: VFR. Breezy. Slight chance
SHRA.

Monday: VFR. Breezy. Chance SHRA.

&&

.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.

Areas of fog this morning, especially east of Cape Cod and
Nantucket. SW gusts increase up to 20 kt today, with fog re- 
developing on the southern waters tonight. Any fog should
dissipate during Friday morning.

Outlook /Friday Night through Monday/... 

Friday Night through Saturday: Winds less than 25 kt. Slight
chance of rain showers, isolated thunderstorms. 

Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers. 

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

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

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

&&

.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...Belk/RM
NEAR TERM...Belk/BW/RM
SHORT TERM...Belk
LONG TERM...RM
AVIATION...Belk/BW/RM
MARINE...Belk/RM
CLIMATE...
      

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