Lexington Weather

Lexington, Massachusetts, USA

59°F

6/17/2026 6:15am

Lexington Conditions: Clear
Temperature: 58.5°F / 14.7°C
Dew Point: 53.1°F
Relative Humidity: 82%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.77 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 102355
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
755 PM EDT Wed Jun 10 2026

.WHAT HAS CHANGED...
Small Craft Advisory issued for the southern outer waters from
06z Thursday to 00z Friday. 

&&

.KEY MESSAGES...

- Scattered showers and isolated thunderstorms expected
  overnight. 

- Heat Advisories advisories remain in effect for northern
  Connecticut and much of interior Massachusetts from noon 
  Thursday to 8pm Friday.

- A few scattered strong to severe thunderstorms are possible 
  Thursday and Friday. 

- Above normal temperatures continue into next week. Decreasing 
  humidity as well. Weekend looking mostly dry, while 
  uncertainty remains high regarding potential for rain showers 
  early next week.

&&

.DISCUSSION...
.KEY MESSAGE 1...Scattered showers and isolated thunderstorms  
expected overnight.

An approaching warm front pushes into the region overnight
bringing a round of scattered showers and isolated elevated
thunderstorms. Potential for severe will be held at bay as 0-6km 
Bulk Shear values stay below 15kts. Still, some of the machine 
learning guidance shows a slight (5-15%) chance for some
stronger storms. Notably, the HRRR Neural Network still
highlights the potential for severe winds across far northern
Massachusetts overnight. Higher confidence part of the forecast 
is areas of heavy rain as PWATs surge to 1.9"-2.0" across most 
of southern New England overnight into Thursday morning. The 
exact corridor of the most concentrated precipitation is still 
somewhat uncertain as forcing will be somewhat weak and
nebulous. There may be two corridors of heavier rain, one near
northwestern Mass, and the other across the Cape and Islands as 
a weak low pressure passes offshore. 


KEY MESSAGE 2...Heat Advisories advisories remain in effect for  
northern Connecticut and much of interior Massachusetts from 
noon Thursday to 8pm Friday.

The warmest air mass of the season so far arrives Thursday and 
Friday as 925 mb temperatures soar to +25-29C. In addition to 
the heat, humidity will increase behind a warm front as it moves
north of our CWA. Southwest flow brings oppressive 65-70 degree
dew point temperatures especially across interior MA and 
northern CT. These high dew points combined with temperatures 
climbing into the low to mid 90s will lead to heat index values 
approaching the upper 90s to near 100F Thursday and likely above
100F Friday across the CT River Valley. As such, Heat 
Advisories remain in effect for these areas through 8pm Friday. 

By Friday, a backdoor cold front will provide some relief from
the heat as onshore flow develop. Lowest temperatures will be 
found mainly east of 495. Further inland, temperatures soar to 
the middle and perhaps upper 90s with heat index values as high 
as 100-101 degrees for the CT River Valley. Moderate heat-
related impacts expand across the region, with major impacts 
expected in the CT River Valley, both Thursday and Friday, 
leading to an increased risk of heat-related illness for anyone 
spending extended time outdoors without adequate hydration or 
access to cooling.

There is still some uncertainty as to how far east heat index
values >95F expand. The latest guidance shows apparent
temperatures increasing to between 90 and 95 degrees in the
Merrimack Valley. While just below heat advisory criteria, these 
temperatures are no less dangerous to those without adequate 
hydration or cooling. 


KEY MESSAGE 3...A few scattered strong to severe thunderstorms
are possible Thursday and Friday. 

The increased heat and humidity set the stage for impressive
levels of instability Thursday and Friday. In terms of aggregate 
severe weather probabilites, machine learning guidance continues
to show a 15-20 percent chance for severe wind potential
Thursday and Friday. In terms of CAPE, guidance continues to
show moderate destabilization with values approaching 1500-2000 
J/kg across the region. The limiting factor will be weak shear 
as values of 0-6km Bulk Shear struggle to get above 20kts
Thursday afternoon. Forcing will also be weak and confined to 
western portions of the CWA. Guidance shows only modest height 
falls as a weak shortwave moves through the region Thursday 
evening. Still, any storms that do form will have the
opportunity to tap into the richly buoyant and unstable airmass. 
Notably, forecast soundings show mid level lapse rates around 
6-7.5C/km Thursday afternoon and evening. The primary threat 
with any stronger storm would be cold pool-driven damaging 
winds. 

KEY MESSAGE 4...Above normal temperatures continue into next
week. Decreasing humidity as well. Weekend looking mostly dry,
while uncertainty remains high regarding potential for rain 
showers early next week. 

A weak high pressure sandwiched between two fronts should
dominate our weather for most of this weekend. The main impact
of these fronts will be lowered humidity. It should still be 
plenty warm for most, if not outright hot. At least the peak 
heat index values should remain mainly in the 80s, with a few 
locations reaching the lower 90s.

Still quite a bit of uncertainty with the details of the
forecast early next week. The latest guidance stalls yet another 
front towards the south coast of New England as a weak low
pressure develops towards NJ sometime Monday night into Tuesday. 
The forcing looks rather weak, but cannot completely dismiss the
idea of scattered showers in our area at times. A subtle shift 
of even just 20 miles to the south, and the forecast could be 
largely dry. This is one of those details yet to be ironed out. 
Changes with later forecasts are expected.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...

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

Through Tonight...Moderate confidence.

Made some changes to the forecast this evening as much of
southern New England remained VFR and dry. Stratus was moving
north from the south coast of New England. Latest thinking based
on latest CAMs is that the convection across upstate NY should
track north of our region. Meanwhile, the convection near the NJ
coast should pass close to the Cape and islands after midnight
tonight. An area of weaker -SHRA could pass in between these two
areas after midnight as well. This would be best times by the
showers around KELM as of this writing.

The northward extent of the MVFR, and especially the IFR,
stratus is not certain. Thinking MVFR is most likely at BOS,
with IFR generally south of a line from KGHG-KSFZ-KIJD.

Winds become light as an inversion moves overhead later tonight.

Thursday...Moderate confidence.

Generally MVFR/IFR conditions. Improvement from showers and fog
overnight will likely be slow (not until 12z or later). Some 
areas could be on the cusp of LIFR conditions as any lingering 
showers push offshore. SW winds continue through the morning 
hours, generally around 10 kts once showers move out.

KBOS Terminal...High confidence in trends. Moderate confidence 
in timing.

KBDL Terminal...High confidence in trends. Moderate confidence 
in timing.

Outlook /Thursday Night through Monday/...

Friday: VFR. Chance SHRA, slight chance TSRA.

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

Saturday through Saturday Night: VFR. 

Sunday: VFR. Breezy. 

Sunday Night: VFR. Breezy. Chance SHRA, slight chance TSRA.

Monday: VFR. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Thursday...High confidence.

Seas 2-4 feet for the majority of the waters except 3-5 feet
across the southern outer waters overnight. SW winds increase to
15-25 kt with gusts as high as 30 kts. Areas of showers and
perhaps a thunderstorm or two through Thursday morning. SCA
conditions continue for the southern waters Thursday before
gradually subsiding by the evening. 

Outlook /Thursday Night through Monday/...

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

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

Saturday through Sunday: Winds less than 25 kt. 

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

Monday: Winds less than 25 kt. Chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory from noon Thursday to 8 PM EDT Friday for 
     CTZ002>004.
MA...Heat Advisory from noon Thursday to 8 PM EDT Friday for MAZ002-
     003-008>011.
     Air Quality Alert from 11 AM to 8 PM EDT Thursday for MAZ013-
     016>024.
RI...Air Quality Alert from 11 AM to 8 PM EDT Thursday for 
     RIZ001>008.
MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Thursday for 
     ANZ254>256.

&&

$$

DISCUSSION...Belk/FT
AVIATION...Belk/Hrencecin/FT
MARINE...McMinn