Lexington Weather

Lexington, Massachusetts, USA

50°F

5/24/2025 12:21am

Lexington Conditions: Overcast
Temperature: 50.4°F / 10.2°C
Dew Point: 48.7°F
Relative Humidity: 94%
Wind: W 1 mph, 10-min avg: 2 mph, gust: 5 mph
Barometer: 29.75 in Steady
Visibility: 10 miles
Rain Today: 0.01 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 180649
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
249 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 conditons, 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/...
230 AM Update:

Key Messages:

* Partial sun early today, but turns mostly cloudy late this
  morning into afternon, with hit- or-miss showers to dodge. No
  washouts though.

* Increasing westerly breezes to around 20-25 mph.

* Highs low 70s coastal plain, RI and most of CT, but could stay
  in the lower to mid 60s. A bit less humid, too.

Details: 

Surface analysis shows a frontal occlusion boundary was just 
about to clear into the waters east of Cape Cod as of early this
morning. Conditions are much less active compared to the last 
couple nights with less fog or storms around, but there is still
quite a bit of at least mid- level cloud cover across most of 
Southern New England. The culprit is associated moisture owing 
to a well- developed upper level low seen quite well on water 
vapor imagery circulating slowly ESE in vicinity of Kingston, ON
and moving into the Tug Hill of NY. There are even some spotty
rain showers in its vicinity mainly N/W of Albany, NY. This 
upper level low and its associated residual moisture and cold 
pocket of air aloft will be the main driver of our weather for 
today and also into Monday. Really not much airmass change so 
far behind the frontal occlusion early this morning, with a 
modest west wind, temps in the upper 50s to low-mid 60s and 
dewpoints mid 50s to low 60s. But that will change as we move 
through the day today.

The upper level low is progged to move eastward across VT/NH
thru early tonight, although we'll still feel the effects of its
broader cyclonic flow aloft here in Southern New England. Could
see some early breaks in the midlevel cloudiness and some early
peeks of sun. As the upper low begins to near our area, quite a
bit of moisture will fill southeastward; this will lead to
mostly cloudy conditions as stratocumulus fills the sky. Cold
advection aloft (925 mb temps tumble to +8 to +10C) with the
moisture could generate some hit-or-miss instability light
showers, more concentrated mainly along and north of the Mass 
Pike closer to the upper level feature, but I couldn't rule out
showers to dodge anywhere. Expect these shower possibilities
during the mid-morning to mid-afternoon, with PoPs around 15-30%
for isolated to scattered showers. No washouts though. A 
tightening westerly gradient will also lead to increased breezes
with dewpoints falling into the upper 40s to low 50s. 

All in all a somewhat unsettled day, but not looking at active 
weather. Westerly breezes to around 20-25 mph, hit or miss 
showers and increased cloudiness. Highs in the coastal plain and
RI/CT should still reach near 70 degrees with falling dewpoints,
but in the interior where cloud cover should trend to overcast,
temps may struggle to reach the lower to mid 60s.

&&

.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 faciliate 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 /07Z SUNDAY THROUGH THURSDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

06z TAF Update: 

Through 12z Sunday: High confidence. 

VFR mostly midlevel clouds. West winds around 5 kt, but 
increase toward morning to around 10 kt.

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 beocmes 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 from 8 AM this morning to 8 PM EDT Monday 
     for ANZ232>235-237-254>256.

&&

$$

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