Lexington Weather

Lexington, Massachusetts, USA

88°F
8/8/2022 6:15pm 
  • Lexington Conditions: Clear
  • Temperature: 88.0°F / 31.1°CColder 3.8°F than last hour.
  • Dew Point: 73.8°FDecreased 1.6°Fsince last hour.
  • Relative Humidity: 63%Increased 4.0% since last hour.
  • Wind: Wind from WSW WSW 14 mph, 10-min avg: 2 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 031947
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
347 PM EDT Wed Aug 3 2022

.SYNOPSIS...
Heat and humidity will be the main weather story right through
this weekend into early next week. The heat and humidity will 
peak tomorrow and Friday, with near record high temperatures 
and oppressive heat indices as well. The greatest potential for 
showers and thunderstorms will be on Friday with even some 
localized heavy rainfall possible.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
330 PM Update: 

While still rather humid across Cape Cod and the Islands, it's 
otherwise a warm but less humid afternoon across Southern New 
England, with local sea-breezes near the eastern and southern 
coasts. Shallow cumulus clouds dot the skies but otherwise mostly 
sunny skies with temperatures in the 80s to low 90s, though in the 
upper 70s to low 80s for coastal MA and RI.

A 1016 mb high pressure area over the northern portion of Cape Cod 
Bay will continue to move southeastward into the offshore waters 
tonight. Clear skies to prevail tonight, though increasing southerly 
to southwest flow will transport higher dewpoints (mid to upper 60s 
inland, low 70s toward southern waters) northward later tonight and 
especially overnight. This should result in re-developing mist/fog 
and stratus fields initially towards the southern coastal waters and 
the adjacent Islands toward late evening or midnight, then tending 
to expand north/northwest into the south coast. Its northwestern 
extent is a little uncertain given S/SW winds but we could see some 
expansion of mist/fog toward central and northern RI into SE MA. 
Lows mid 60s to low 70s. 

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
330 PM Update:

Thursday:  

Any overnight stratus/fog near southeast New England should 
dissipate by mid morning. 

Thereafter we are looking at hot and humid weather with temperatures 
expected to rise quickly under full sun and 850-925 mb warm 
advection. GFS is on the higher end of this range with 850 mb temps 
reaching around +21 to +22C. However in looking at the NAM and 
ECMWF, values are a couple degrees cooler. It really won't make much 
difference because southwest breezes will also add an element of 
downsloping and produce air temps in the mid to upper 90s and lower 
80s for southeast New England. Will also mention that skies could be 
rather hazy as HRRR-Smoke model vertically integrated smoke shows a 
plume of high-altitude smoke from wildfires in the western states. 

Heat Advisories were maintained with this forecast package with heat 
indices up to 104F. A few areas 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 wasn't high enough for a large enough area to consider 
upgrading. Source air for dewpoints tomorrow looks to be across the 
central and southern Appalachians where current values are in the 
upper 60s to low 70s. While it still will be rather humid, WSW 
downsloping will help to reduce dewpoints a little, which cuts into 
how high heat indices get. There may be either convective cloud 
debris from convection over NY and/or isolated storms moving into 
western MA/CT later in the day. There is strong confidence in heat 
indices between 95 to 104 for most of Southern New England. So the 
message however is the same when it comes to the heat and 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.

Thursday Night: 

Any isolated garden-variety thunderstorms in western MA and western 
CT should weaken and fizzle shortly after sundown. A warm and muggy 
night is in store with continued southerly flow. This will also 
transport tropical low to mid 70s dewpoints northward. 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.

&&

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

* Oppressive heat and humidity continues Friday. Heat Advisory 
  in effect.

* Scattered showers and thunderstorms Friday afternoon with
  local heavy rainfall possible

* Hot/humid weather continues trough the weekend and into early
  next week. Additional heat headlines possible

Thursday night and Friday

Pronounced Bermuda high pressure system continues to pump hot
and humid air into the northeast Thursday night into Friday. 
Dewpoints surge overnight Thursday into Friday across southern 
New England, rising into the low to mid 70s. Thus, expect 
Thursday night to consist of very uncomfortable sleeping 
weather.

Current heat advisory extends into Friday as we'll have a 
second consecutive day of 850 temps near 20 Celsius supporting 
surface temps in the mid to upper 90s at the surface across 
southern New England. While temperatures are not expected to be 
as warm as what is expected Thursday (see short term AFD) the 
increased humidity will have heat indices well over 100 degrees 
again on Friday afternoon. Also can't rule out heat indices 
perhaps eclipsing the 105 mark which would warrant excessive 
heat warning headlines. Confidence in reaching that mark is low 
at this time, so we're hanging on to the heat advisory in the 
mean time. Highest heat indices expected to reside across the CT
and Merrimack River valleys.

Some relief will be possible Friday afternoon as a weak surface
cold front drops into southern New England. While the forcing 
associated with this front is expected to be weak, it should be 
enough to initiate scattered convective showers and 
thunderstorms across the northern and western areas of southern 
New England. Weak wind fields will suppress the severe 
thunderstorm threat, but also introduce the possibility for slow
moving storms that will have the ability to produce much needed
locally heavy rainfall. 

This Weekend

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 may be needed this weekend. 
Heat and humidity will also support an unstable atmosphere 
during the afternoon hours which will bring isolated 
shower/thunderstorm chances each afternoon through Monday. May 
see temperatures and humidity moderate early next week with a 
cold frontal passage possible during the Monday to Tuesday time 
frame.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
Forecaster Confidence Levels:

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

18z TAF Update:

Rest of the Afternoon (thru 00z Thu): High confidence. 

VFR. S/SE winds (more SE near the eastern MA coast) around 5-10
kt. 

Tonight: High confidence in trends, moderate on extent of
fog/stratus. 

VFR early, then will start to see LIFR mist/fog and stratus develop
near ACK and spread northwestward toward at least the South 
Coast, Cape Cod, MVY and BID. Looks like IFR fog or stratus may 
advance as far northward as PVD, but how far north is a question
given S/SW flow. Most areas along/north of the Mass Pike to
stay VFR. 

Thursday: High confidence. 

Fog/stratus dissipates by 13z. VFR with hazy skies aloft. Low
prob of isolated TSRA in far western New England/Berkshires
after 22z. SW winds 8-13 kt gusts to 18-20 kt. 

Thursday Night: Moderate confidence. 

Generally VFR. Status/fog may return overnight to the South 
Coast, Cape and Islands.

KBOS...High confidence in TAF. 

KBDL...High confidence in TAF. 

Outlook /Friday through Monday/...

Friday: Mainly VFR, with local MVFR possible. Chance SHRA,
slight chance TSRA.

Friday Night: VFR. Chance SHRA, slight chance TSRA.

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

Saturday Night: VFR. Breezy. 

Sunday through Sunday Night: VFR. Breezy. Slight chance SHRA,
isolated TSRA.

Monday: VFR. Breezy. Chance SHRA, slight chance 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 tranquil through the period. 

Winds become S/SW tonight around 10 kt with fog re-developing near 
the south coastal waters. SW gusts increase to 15 to 20 kt Thursday, 
with fog re-developing on the southern waters Thursday night. Seas 
continue at 3 ft or less for all waters.

Outlook /Friday through Monday/... 

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

Friday Night: Winds less than 25 kt. Chance of rain showers,
slight chance of thunderstorms. 

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

Saturday Night: Winds less than 25 kt. 

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

Sunday Night through Monday: Winds less than 25 kt. Seas up to
5 ft. Slight 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 from 11 AM to 11 PM EDT Thursday for CTZ002.
     Heat Advisory from 11 AM Thursday to 8 PM EDT Friday for 
     CTZ002>004.
MA...Air Quality Alert from 11 AM to 11 PM EDT Thursday for 
     MAZ005>007-010>012-014.
     Heat Advisory from 11 AM Thursday to 8 PM EDT Friday for 
     MAZ002>021-026.
RI...Heat Advisory from 11 AM Thursday to 8 PM EDT Friday for 
     RIZ001>007.
MARINE...None.

&&

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

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