Old Res Weather

Lexington, Massachusetts, USA

35°F

2/16/2025 7:17pm

Lexington Conditions: Clear
Temperature: 35.1°F / 1.7°C
Dew Point: 32.4°F
Relative Humidity: 90%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.00 in Falling Slowly
Visibility: 10 miles
Rain Today: 0.01 in
UV Index: $VPuv None

Southeast Middlesex County, MA - Heat Advisory
- SEE ALL NEARBY ALERTS -

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 101836
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
236 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 0-6 km 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 /18Z WEDNESDAY THROUGH MONDAY/...
Forecaster Confidence Levels...

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

Through Tonight...High confidence to start, moderate confidence
towards the nighttime hours.

VFR conditions continue for the rest of the afternoon. Some 
MVFR to localized IFR conditions may overspread parts of the 
region from southwest to northeast by early this evening along 
with a few showers. Showers become more likely tonight and
coverage looks limited as the activity makes its way from west
to east. Greater chance for -TSRA/-SHRA across western
terminals.

Gusts to around 20 kt continue thru the early evening SW winds 
will shift more S in the wake of a passing warm front later 
today into tonight. Winds become light as an inversion moves
overhead.

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. TEMPO for -SHRA continues from 01-05z.

KBDL Terminal...High confidence in trends. Moderate confidence 
in timing. Timing for SHRA and later TSRA still a bit uncertain.
Included as TEMPOs for now.

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.
RI...None.
MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Thursday for 
     ANZ254>256.

&&

$$

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