Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 141748
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
148 PM EDT Tue Jul 14 2026

.WHAT HAS CHANGED...
Added western Hampden County to the Heat Advisory, and issued 
rip current statements for south-facing beaches today through
Wednesday with potential for dangerous rip currents and surf.

&&

.KEY MESSAGES...

- Hazy, hot and humid today and Wednesday.

- Strong thunderstorms possible early overnight tonight and/or into 
Wednesday.

- Dangerous rip currents and surf expected on south-facing beaches 
today and Wednesday.

- More seasonable temperatures and less humid late week into the 
weekend, but still unsettled with chances for showers and 
thunderstorms, with the best chance this weekend.

&&

.DISCUSSION...
KEY MESSAGE 1...Hazy, hot and humid today and Wednesday.

Main story today through Wednesday is the hot temperatures with some 
humidity with it, associated with a plume of 850 mb temperatures in 
the low 20s C range which begin to advect in today from the west-
northwest. Heat Advisories remain in effect, as temperatures project 
to reach into the mid to upper 90s away from the Cape and the 
Islands today and end up slightly cooler on Wednesday. Certainly 
want to limit exposure outdoors today and Wednesday if possible; but 
this spell of heat should be a little different compared to the 
early-July oppressive heat and humidity we had. For one, both days 
feature pretty strong southwesterly breezes with peak gusts in the 
25-30 mph range, and upwards of 35 mph towards the Cape and Islands 
which tend to blow pretty strongly on SW winds. Second, the 
southwest downsloped winds and some mixing should allow for 
dewpoints to stay in the mid to upper 60s: humid, but not the air-
you-can-wear type oppressive humidity. Not sure it's fair to call it 
a dry heat, but compared to the early-July stretch, it could be 
construed that way. Thirdly, at least for today, the 00z HRRR-Smoke 
guidance progs a pretty sizable concentration of vertically-
integrated smoke across a large part of the Northeast early this 
afternoon advecting in from the fires burning in northern MN and 
portions of central Canada. This smoke layer looks constrained to 
being aloft so no risk for health problems from it, but its possible 
that it could temper full sun to an extent with a hazier look to the 
sky if it's as concentrated as progged to be. For Wednesday, one of 
the bigger flies in the ointment at least for the northern portion 
of the Advisory is the timing of a cool front. Latest guidance shows 
this front now nearing the MA border by the pre-dawn hrs, then 
moving southward through the morning hrs to the MA Pike and to the 
southern coast later in the day. Could make the Advisory a bit 
borderline if we do get an early-day passage, as dewpoints tumble 
behind its passage. Heat indices today in the mid 90s to low 100s 
today, but could be closer to the low 90s north and mid/upper 90s 
south of the Pike Wednesday.

KEY MESSAGE 2...Strong thunderstorms possible early overnight 
tonight and/or into Wednesday.

This is the more uncertain element of the forecast the next couple 
days. Still looks as though northern New England has the greatest 
risk for severe weather today into part of tonight, with as much as 
a Enhanced (Level 3 of 5) risk for severe weather in northern ME, NH 
and VT. In Southern New England, we look capped to convection today 
and into part of tonight per bufkit sounding profiles, but there 
remains a large amount of instability above that capping inversion, 
in some solutions upwards of 2500-3000 J/kg of CAPE using an average 
parcel in the lowest 100 mb of atmosphere. Some of the high-res 
guidance is beginning to come around to the idea of showing 
convective development trailing back westward along a cold front 
with a weakening capping inversion into central VT/NH as soon as 
early overnight; but the timing and coverage of this activity still 
is pretty scattershot across the high-res suite. This could 
ultimately end up being a nowcast situation, but given this trend I 
couldn't really justify NBM's nil PoPs. Opted for up to 30% PoP 
along the MA/NH/VT border between 4-7 AM Wed, then slowly sagging 
southward through the day. If any storms develop, they would 
likely become strong to potentially severe quickly given the 
degree of instability aloft and pretty strong NW mid-level 
winds, with frequent lightning, hail and strong straight line 
winds all possible, potentially early in the day as well. Low 
confidence but potentially higher impact if storms can 
materialize.

KEY MESSAGE 3...Dangerous rip currents and surf expected on south-
facing beaches today and Wednesday.

SW breezes expected today and again on Wednesday will end up 
building wave heights later today into tonight to around 5-8 ft on 
the outer waters, then start to lower into the 4-6 ft range for 
Wednesday but becoming longer in period. This poses a risk for 
dangerous rip currents and higher surf, and though it's often 
bullish in its output, it is supported by NWPS high probabilities 
for rip currents. Given the hot temperatures expected today and 
again on Wednesday, we should see an anticipated increase in people 
venturing to the beaches. For that reason we've hoisted a rip 
current statement for today and ran it through Wednesday early 
evening for the southern coastline, with those areas with 
south/southwest facing exposures most at-risk. There should be fewer 
numbers of people at beaches at night but since the waves look to be 
higher tonight, opted to not get cute with the timing. the Wave 
periods are on the shorter side today which could reduce wave energy 
to an extent, as it's often the longer period waves which cause the 
biggest risk for rip currents. Swim near vicinity of lifeguards and 
stay off jetties.  

KEY MESSAGE 4...More seasonable temperatures and less humid late 
week into the weekend, but still unsettled with chances for showers 
and thunderstorms, with the best chance this weekend. 

Upper low to our northeast drives a fast, but broadly cyclonic flow 
aloft into Southern New England most of this period. After the cool 
front moves southward into early Thursday morning, seasonable 
temperatures in the low to mid 80s return with less humidity. We'll 
have to watch for any ripple in the NW flow aloft thru late this 
week, which could trigger showers/storms, but too uncertain at this 
time. Ensembles continue to offer a wetter weather pattern evolving 
this weekend which offers the next best chance for needed rainfall.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...

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

18z TAF Update:  

Today and Tonight: High confidence. 

VFR continues at all terminals. Hazy skies continue through the
afternoon due to high- altitude smoke from fires in central 
Canada, and have continued with the mention of SCT-BKN200 decks
in TAFs. Gusty SW winds 19-26kt will persist through the evening
hours, gradually subsiding for most terminals except along the
Cape and Islands. Areas of LLWS will be possible for KFMH, KHYA
& KACK with a strong 40-50kt LLJ moving overhead. 

Wednesday: Moderate confidence.

Mainly VFR conditions throughout, however some visibility
restrictions may be possible across western MA & CT due to
increasing near surface smoke from Canadian wildfires.
Additionally, tomorrow morning/afternoon some isol-sct showers 
may be possible for northern terminals, however no mention of 
VCSH/VCTS have been included at this time given the uncertainty 
in timing and coverage. Winds will become more W/NW after 07-10z
becoming gusty 20-25kt once again in the afternoon.

KBOS Terminal...Moderate Confidence.

Minor visibility restrictions are possible on Wednesday due to 
concentrations of surface smoke from Canadian wild fires. 
Visibilities may drop to around 5-6sm. 


KBDL Terminal...Moderate confidence.

MVFR visibility restrictions are possible on Wednesday due to 
surface smoke from Canadian wild fires.

Outlook /Wednesday Night through Sunday/...

Thursday through Thursday Night: VFR. Breezy. 

Friday through Friday Night: VFR. 

Saturday: VFR. Slight chance SHRA.

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

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

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Wednesday: High confidence. 

SCAs take effect today and were extended into Wednesday. SW
winds increase today to around 25-30 kt, with low prob of gusts
to gale force near the Cape and Islands today into tonight, with
seas building to 6-8 ft offshore by tonight. Seas then slowly
ease into Wednesday but should still be in the SCA range for
Wednesday. Potential for thunderstorms on the northern waters as
soon as overnight tonight into early Wed AM, with lesser risk
for thunderstorms on the southern waters Wed aftn/night.

Outlook /Wednesday Night through Sunday/...

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

Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. 

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

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

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

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

Sunday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain
showers. 

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT Wednesday for CTZ002>004.
MA...Heat Advisory until 8 PM EDT Wednesday for MAZ003>007-010>021-
     026.
     Heat Advisory until 8 PM EDT this evening for MAZ009.
     Air Quality Alert until 11 PM EDT this evening for MAZ017>024.
     High Risk for Rip Currents through Wednesday evening for MAZ020>024.
RI...Heat Advisory until 8 PM EDT Wednesday for RIZ001>007.
     Air Quality Alert until 11 PM EDT this evening for RIZ001>008.
     High Risk for Rip Currents through Wednesday evening for RIZ006>008.
MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ230-
     231-250-251.
     Small Craft Advisory until 8 PM EDT Wednesday for ANZ232>235-
     237-254>256.
     Small Craft Advisory until 11 PM EDT this evening for ANZ236.

&&

$$

DISCUSSION...Loconto
AVIATION...Belk/Guest
MARINE...Loconto