Lexington Weather

Lexington, Massachusetts, USA

50°F

5/24/2025 12:05am

Lexington Conditions: Overcast
Temperature: 50.4°F / 10.2°C
Dew Point: 48.4°F
Relative Humidity: 93%
Wind: WSW 2 mph, 10-min avg: 2 mph, gust: 7 mph
Barometer: 29.75 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 181330
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
930 AM EDT Sun May 18 2025

.SYNOPSIS...

An upper level low pressure will track across northern New
England today and into the Canadian Maritimes on Monday. This
will bring cooler and less humid conditions, but also generally
unsettled weather with cloud cover and hit or miss showers
mainly north of the Massachusetts Turnpike. A cooling trend 
sets in Tuesday that will continue through the week. Unsettled 
weather returns once again in the second half of the week into 
the weekend.

&&

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

Key Messages...

* Considerable clouds overspread the region from the west today
  with highs mainly upper 60s/lower 70s and a bit of a breeze

* A few spot showers possible this afternoon mainly north of
  I-90...but the vast majority of the day will remain dry

A closed upper level low across northern New England will result
in cyclonic flow across the region today. This will result in 
broken deck of strato-cu overspreading the region from west to 
east through the afternoon. The cold pool aloft coupled with 
shortwave energy may trigger a few spot showers later 
today...mainly north of I-90. However...the vast majority of the
day will be dry with the bulk of the showers in northern New 
England closer to the closed upper level low. 

High temps today will mainly be in the upper 60s to the lower
70s...although a few degrees cooler across the interior high
terrain. A westerly breeze of 20-25 mph and decreasing humidity
will make it feel cooler compared to the weather.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...

230 AM Update:

Key Messages:

* Turns breezy and cooler, drier and much less humid tonight,
  with partly cloudy skies. Lows mid 40s to low 50s.

* These conditions last into Monday, with less clouds south and
  west and more north. Highs mainly in the 60s, but northwest
  breezes could make it feel cooler.

Details: 

The upper low will continue to pull into Maine tonight, then
slowly progress into the Maritimes on Monday. This will create a
strengthening NWly pressure gradient tonight which lasts into
Monday, along with strong cold and dry advection. 

Expect any instability type showers to dissipate shortly after
sundown this evening. The real noticeable airmass change then 
comes in as northwest winds pick up, with speeds 10-15 mph and 
gusts in the 25-30 mph range. Dewpoints fall into the 40s, so it
should feel noticeably less humid compared to the last couple 
days. Our 925 mb temps then turn unseasonably cool, falling to 
around +3 to +5C by early Monday morning! Expect mostly clear to
partly cloudy skies, greatest north, but the strengthening 
winds overnight should keep temps in the mid 40s to lower to 
mid 50s.

Monday features variable amts of cloud cover, with less
cloudiness toward mostly sunny conditions south and west, and
quite a bit more across northern and northeast MA closer to the
upper level circulation. More sunshine will facilitate stronger
mixing too, with NWly gusts around 25-35 mph. Although the sun 
should be enough to keep temps closer to the mid 60s - near 70, 
temps could struggle to reach 60 degrees in northeast MA/North 
Shore area, and the breezes could make it feel cooler than that.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Key Messages:

* Cooling trend starts Tuesday and continues through the rest of the 
  week

* Another system will likely bring rain and gusty winds to southern 
  New England in the second half of the week

Details...

Not much has changed in the early part of this period. An upper 
level low makes its exit offshore towards the Maritimes Monday 
night. Northwest flow kicks in while cooler temperatures aloft 
remain, which will help keep the region cooler and drier. Winds 
shift to the northeast Tuesday into Tuesday night as the low 
continues offshore. Highs Tuesday through Friday are expected to be 
mostly in the 50s and low 60s.

A surface low is expected to move up along the east coast towards 
southern New England. This late spring Nor'Easter could bring 
significant rainfall and gusty winds starting sometime in the early 
hours of Thursday through Friday. Timing is starting to get more 
defined, with ensembles starting to agree on the low passing to the 
southeast Thursday afternoon/evening. There is still significant 
variance in its track though. The GEM tracks its center right over 
SE MA, while the GFS and ECMWF track it to the southeast of 
Nantucket (though the GFS keeps it further offshore). This is 
uncertainty is also seen in the different ensembles' 24 hour QPF 
values, where they range from around 0.35" across southern New 
England (GEFS) up to an inch in some areas (ECMWF ENS). If the storm 
remains closer to the coast, we can expect more rain and gustier 
winds. Both decrease if the low tracks further offshore. NAEFS 
guidance also signals PWATs about a standard deviation above normal 
remaining well offshore. Even so, wetting rains can be expected. The 
overall consensus is that the end of next week will be unsettled and 
cool with continued broad cyclonic flow and cooler temperatures 
aloft.

&&

.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

12z TAF Update:

Today: High confidence. 

VFR for most, though trends to BKN-OVC VFR/MVFR range after 14z
interior and around 16-18z for the coastal plain. Better chance
at MVFR bases for ORH, BDL and BAF. Hit-or-miss -SHRA mid-
morning thru sundown but won't restrict visbys. W breezes 10-15
kt with gusts 20-25 kt.

Tonight thru Monday: High confidence.

VFR. Windshift to NW around 10-15 kt with gusts to 25 kt
tonight, which increase to around 15 kt with gusts 25-30 kt on
Monday.

KBOS TAF...High confidence. Mainly SCT-BKN VFR cigs, though 
wouldn't entirely dismiss a 025-030 base this afternoon. Hit or
miss showers possible but better chance north and west. W winds
increase to around 10-13 kt with gusts 20-24 kt today, then
shift to NW tonight and increase to 15 kt with gusts 25-28 kt. 

KBDL TAF...High confidence. SCT-BKN VFR ceilings into the mid-
morning hours, then becomes BKN/OVC MVFR with hit-or-miss
showers late morning to sundown. Improves back to VFR tonight. W
winds increase to around 10-12 kt with gusts 20-25 kt range
today, then becomes NW and increases to 15 kt / gusts to 25-28
kt tonight and overnight. 

Outlook /Monday Night through Thursday/...

Monday Night through Tuesday: Mainly VFR, with local MVFR
possible. Breezy. 

Tuesday Night: Mainly VFR, with areas MVFR possible. Slight
chance SHRA.

Wednesday: MVFR/IFR conditions possible. Chance SHRA.

Wednesday Night: MVFR/IFR conditions possible. Breezy. SHRA
likely.

Thursday: Mainly MVFR, with areas IFR possible. Breezy. SHRA
likely.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Monday: High Confidence.

An upper level low will track across northern New England today,
then move into the Gulf of Maine tonight and into Canadian
Maritimes Mon. 

W wind gusts increase to around 20-25 kt on most waters this
afternoon, with a windshift to NW around 25-30 kt on most waters
tonight and into Monday. Offshore flow should limit wave heights
to around 3-5 ft, though some 6 footers possible on southern
waters. Small craft advisories remain posted.

Outlook /Monday Night through Thursday/...

Monday Night through Tuesday Night: Winds less than 25 kt.
Areas of seas approaching 5 ft. 

Wednesday: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers. 

Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers. 

Thursday: Strong winds with gusts up to 25 kt. Rough seas up to
10 ft. Rain showers likely.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Monday for ANZ230-
     231-236-250-251.
     Small Craft Advisory until 8 PM EDT Monday for ANZ232>235-237-
     254>256.

&&

$$

SYNOPSIS...Loconto/Hrencecin
NEAR TERM...Frank
SHORT TERM...Loconto
LONG TERM...Hrencecin
AVIATION...Loconto/Hrencecin
MARINE...Loconto/Hrencecin