Lexington Weather

Lexington, Massachusetts, USA

67°F

6/21/2025 1:25am

Lexington Conditions:
Temperature: 67.3°F / 19.6°C
Dew Point: 56.8°F
Relative Humidity: 69%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.93 in Rising Slowly
Rain Today: 0.00 in

Southeast Middlesex County, MA - Extreme Heat Watch
- SEE ALL NEARBY ALERTS -

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 192335
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
735 PM EDT Thu Jun 19 2025

.SYNOPSIS...
High heat and humidity today with strong to severe thunderstorms 
possible this afternoon and evening. The best chance of severe 
weather today is in interior Southern New England. Turning drier and 
much less humid on Friday, but also quite windy by late June 
standards. Seasonably warm temperatures are expected this weekend. 
Monitoring for thunderstorm potential this weekend but the overall 
risk is low. A multi-day stretch of significant heat is looking more 
likely for Monday through Wednesday, with the potential for heat to 
reach dangerous levels.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Key Messages: 

* Heat Advisory in effect through 8PM with apparent temps near triple 
  digits

* Severe thunderstorm risk quickly wanes 


Details:

Heat and Humidity...

A Heat Advisory remains in effect through 8 PM this evening. We've 
already seen several hours of full sun today, and the temperatures 
skyrocketed this morning in response. Expecting temperatures to 
continue to warm into the lower to mid 90s, and with dewpoint 
temperatures in the low to mid 70s, it may feel closer to the low 
100s.

Remember to stay hydrated and limit strenuous outdoor activities 
today. Take frequent breaks in locations with air conditioning and 
wear light weight and light colored clothing.


Strong to Severe Thunderstorms This Afternoon...

The severe threat has quickly waned as earlier convection made
quick work of instability. As a result, the severe thunderstorm
watch has been cancelled. 


&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Key Messages: 

* Sunny and slightly cooler Friday

* High winds likely during the day on Friday

Friday and Friday Night:

Clearing skies and lots of sun combine with a low-level jet around 
40 kts and lead to the likelihood of quite high winds at the surface. 
Thinking we could see areas of 30-45 mph with a few gusts near
50 mph in parts of western, central, and northeastern
Massachusetts and possibly go with a Wind Advisory for Friday. 
Already went with a Gale Warning for Boston Harbor, 
Massachusetts Bay, and Ipswich bay for the day. Wind speeds 
should decrease more steadily into Friday evening.

We'll start to dry out a little bit for the start of the weekend 
once the post-FROPA airmass moves in. Temperatures look to be in the 
mid 80s across the interior and mid to upper 70s across the Cape and 
Islands.&&

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Key Messages:

* More seasonable temperatures for the weekend behind cold front.

* Slight chance for showers and thunderstorms early Saturday but 
  coverage is in question. 

* Multiple days of dangerous heat still expected through mid-week 
  next week. Air temperatures could rise as high as 100 degrees with 
  humidity making things feel even hotter. Greatest chance across 
  the interior, especially in river valleys and urban areas. 


Little in the way of changes with regards to the evolution of the 
upper-level pattern in the 3-7 day range. Heights are still expected 
to  build across the eastern CONUS as a trough deepens over the 
western CONUS. This results in a strong ridge centered over the Ohio 
Valley and Mid Atlantic. Ensemble guidance suggests that 500 
millibar heights rise to as high as 597 dm by Tuesday. This setup 
likely brings the hottest conditions of the season so far starting 
Monday and lasting through Wednesday. Widespread 90's, and even a 
few 100-degree readings will be likely across the region. Locally 
hotter conditions are possible in river valleys where downslope flow 
may warm things by a few degrees. 

Saturday and Sunday:

The warm-up begins Saturday as heights start to build over the 
region. Temperatures will be near to slightly above normal with 
highs rising into the mid and upper 80s except across the Cape and 
Islands where southwesterly flow will likely keep things a bit 
cooler. High temperatures climb a bit more on Sunday, likely 
reaching the upper 80s and lower 90s across the interior. 

Outside of the increasing temperatures, there is a slight chance for 
a few showers or thunderstorms earlier Saturday. A weak shortwave 
moving around the periphery of the building ridge may bring a round 
of showers and storms mainly across northwestern areas. At the 
moment the risk is quite low as the storms will be battling rising 
heights and limited surface instability. 

Through Mid-Week:

Confidence in a significant heat event continues as guidance shows 
near unanimous agreement in dangerously hot conditions. Heat starts 
to build on Monday with ensemble guidance showing probs near 100 
percent for high temperatures >90F across much of the interior. The 
NBM suggests even hotter conditions on Tuesday with widespread 90-
95% probs of high temperatures exceeding 95F! A few spots in area 
river valleys may approach 100 degrees with light westerly downslope 
flow. The idea for widespread heat is further supported by 850mb 
temperatures soaring to +22-24C Monday and Tuesday! This is an 
impressive signal considering we are still more than 120 hours away 
from the event. Some relief is possible Wednesday as low pressure 
passing through the Canadian Maritimes swings a weak backdoor cold 
front through the area. Guidance suggests than an onshore flow 
develops by Wednesday afternoon. The onshore flow could bring a 
relief from the hot weather, mainly for coastal areas and much of 
eastern MA.

&&

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

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

00Z TAF Update:

Tonight: High confidence. 

A low chance for lingering TSRA thru 02z but improvement is
expected at all airports. IFR stratus and fog out over the Cape
and Islands may still linger until we see a gusty westerly 
windshift overnight. SW to W winds increase to around 10-15 kt
with gusts low-20s kt range and LLWS for the Cape and Islands 
from a 40kt westerly low level jet. 

Friday: High confidence. 

VFR. W/WNW winds become gusty by late morning, with speeds 
13-18 kt and gusts 25-35 kt.

KBOS Terminal...High confidence in TAF. 

VFR ceilings with the main concern being gusty west winds. Winds
overnight switch to 240 between 12 and 15 kt. Stronger winds 
arrive around 15z Friday with frequent gusts up to 35 kt. Winds
quickly calm tomorrow night. 

KBDL Terminal...High confidence in TAF. 

IFR VFR ceilings S winds around 10-12 kt with gusts to 20 kt 
this evening, then with a windshift to W around midnight at 
similar speeds. Increasing winds tomorrow with gusts around 35
kt around 15z. Winds slowly calm throughout the afternoon
tomorrow. 

Outlook /Saturday through Tuesday/... 

Saturday: VFR. 

Saturday Night through Sunday: Mainly VFR, with areas MVFR
possible. Breezy. Slight chance SHRA, slight chance TSRA.

Sunday Night: VFR. Breezy. 

Monday through Monday Night: VFR. 

Tuesday: 

&&

.MARINE...
Forecaster Confidence Levels...

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

Small craft advisories have been expanded to all waters starting
this afternoon and were also extended into Friday. SW gusts
today should reach into the 25 kt range, although we expect 
stronger gusts on Friday on all waters to around 30 kt. Gusts 
could approach near gale force at times on Friday. Seas will
also be building today to around 3-5 ft, and then increase to
around 4-7 ft on Friday. 

Because of the building seas and SW to W winds expected for
today and tonight, we've also hoisted a rip current statement
for today and Friday on south-facing beaches. It is somewhat
borderline today, but the threat for dangerous rip currents
should increase tonight and into Friday.

Outlook /Saturday through Tuesday/...

Saturday: Winds less than 25 kt. 

Saturday Night: Winds less than 25 kt. Slight chance of rain
showers. 

Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas locally approaching 5 ft. Slight chance of
rain showers. 

Sunday Night through Tuesday: Winds less than 25 kt. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT this evening for CTZ002>004.
MA...Heat Advisory until 8 PM EDT this evening for MAZ003>007-
     010>019-026.
     High Risk for Rip Currents through Friday evening for MAZ023-024.
RI...Heat Advisory until 8 PM EDT this evening for RIZ001-002.
     High Risk for Rip Currents through Friday evening for RIZ008.
MARINE...Gale Warning from 9 AM to 7 PM EDT Friday for ANZ230-251.
     Small Craft Advisory until 8 PM EDT Friday for ANZ231>237-250-
     254>256.

&&

$$

SYNOPSIS...Frank/McMinn/FT
NEAR TERM...Frank/McMinn
SHORT TERM...Frank/McMinn
LONG TERM...FT
AVIATION...Frank/McMinn
MARINE...