Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 151843
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
243 PM EDT Thu Oct 15 2026

.WHAT HAS CHANGED...

There is a low risk for severe weather Friday between 5 and 11 pm in 
the form of strong to localized damaging wind gusts.

&&

.KEY MESSAGES...

- Brief period of showers mainly Fri morning with a lull in the
  activity much of Fri afternoon outside of a few spot showers.
  Cluster of showers & perhaps a few embedded t-storms with even
  a low risk for severe weather between 5 and 11 pm Fri evening.
  Windy and much cooler Sat with highs in the lower-middle 50s.

- Chilly night Saturday night with below-freezing low temperatures 
  away from the coasts.

- Dry with a modest warmup through early next week, though
  monitoring coastal storminess near or south of the mid-
  Atlantic waters. 


&&

.DISCUSSION...

KEY MESSAGE 1...Brief period of showers mainly Fri morning with a 
lull in the activity much of Fri afternoon outside of a few spot 
showers. Cluster of showers & perhaps a few embedded t-storms with 
even a low risk for severe weather between 5 and 11 pm Fri evening.
Windy and much cooler Sat with highs in the lower-middle 50s.

Large high pressure shifts east of the region tonight as an 
intensifying low pressure moves across the eastern Great Lakes. This 
will allow a return southerly flow of air along with increasing low 
level moisture to work northward into the region overnight. 
Initially...mainly clear skies/light winds will allow for temps to 
fall quickly through the 40s in many locations shortly after sunset 
this evening. However...increasing clouds along with developing low 
level southeast flow will allow for slowly rising temperatures 
toward daybreak.

In addition...the developing southerly LLJ/moisture transport will 
increase the forcing for ascent and allow for a cluster of showers 
to develop toward daybreak across interior southern New England. 
These showers may reach the coastal plain during the early-mid 
morning hours. The showers should be fairly numerous especially 
across northern MA...but the steady showers should be relatively 
short-lived lasting generally 1-3 hours in a given location. 
Otherwise...a good portion of Fri afternoon should feature a lull in 
the activity. A few spot showers certainly will remain 
possible...But much of this period may feature just cloudy skies 
with a breezy southerly wind. Despite lots of clouds...strong warm 
advection should push highs well into the 60s in many locations 
perhaps even near 70 in few spots. Dewpoints reaching or breaking 
60+ will result in a bit of humidity too for the middle of October 
standards. 

The main concern though is between 5 and 11 pm Fri evening as a cold 
front crosses the region. There should be roughly a few hundred J/KG 
of at least elevated Cape ahead of this front. Strong jet 
dynamics/forcing are also depicted ahead of this front with 55-65 
knots of effective shear. The high resolution models generally show 
a line of showers with perhaps some embedded thunder as the cold 
front sweeps across the region. Despite very strong jet 
dynamics...instability is meager...so the severe weather potential 
is low but brief sub-severe wind gusts of 35-50 mph are still 
possible even if the showers do not contain any thunder. 
However...if we end up getting just a bit better moisture return off 
the relatively warm ocean...the low risk for severe weather could be 
realized. The CSU machine learning probabilities as well as the NCAR 
HRRR neural network indicate a low risk for severe weather. Again 
this is a low probability...but it needs to be watched. The main 
risk would be locally strong to damaging wind gusts especially with 
fully leafed trees across most locations.

Otherwise...a much cooler airmass works into the region late Fri 
night and Saturday on quite gusty NW winds. A few lingering showers 
possible into mid-morning Sat near the southeast New England coast. 
Otherwise...windy with northwest wind gusts on the order of 25 to 35 
mph with a few gusts near 40 mph expected on Sat. Despite skies 
becoming partly sunny on Sat...highs will be held in the lower to 
middle 50s. 

KEY MESSAGE 2...Chilly night Saturday night with below-freezing
low temperatures away from the coasts.

After a cool, dry and blustery Saturday, looking at one of the 
coldest nights we've seen to this point in autumn 2026 as broad, and 
strong high pressure settles in over the Northeast. It's still a 
little unclear how quickly the blustery NW winds from the daytime 
hours subside but at least very good radiational cooling conditions 
are anticipated. With a likely cool start, should see lows drop into 
mid 20s to low 30s range for much of Southern New England except in 
the mid 30s for the cities and Cape Cod/Islands. Note that the 
frost/freeze program for Southern New England has ended as of 
October 11th and not expected to resume again until mid-Spring 2027, 
which means freeze/frost headlines won't be issued; however if you 
still have plants/crops outside, you'll want to take the necessary 
precautions to prevent freeze/frost damage. 

KEY MESSAGE 3...Dry with a modest warmup through early next 
week, though monitoring coastal storminess near or south of the 
mid- Atlantic waters. 

The expansive surface high pressure from Saturday night, spanning 
from the Southern Appalachians through Southern New England and the 
Canadian Maritimes, then governs our weather pattern Sunday through 
early next week. This will facilitate a steady warming trend with 
slightly above normal temperatures, with mostly clear skies and 
strong diurnal temperature ranges (milder days, cool nights). 
Looking at highs Sunday in the mid to upper 50s and lows in the 30s. 
Highs by early next week rebound back into the middle 60s with lows 
in the upper 30s/low 40s.

It should be a largely dry period through Tuesday, though the one 
system we'll be monitoring is a closed upper low near the mid-
Atlantic/Carolinas waters, a feature which became detached from the 
broader upper level westerlies along the stalled frontal boundary 
from Friday night and early Saturday. The general position of this 
system is generally agreed upon across the ensemble NWP suite and AI-
based guidance, but there's quite a bit of uncertainty on if we see 
any of this moisture come back northward through the governing 
ridge. That could bring at least enhanced NE breezes, strongest near 
Cape Cod, and possibly some clouds/light rain showers by Tuesday for 
southeast New England. But it's very possible it ends up being 
mainly dry/remains to our south. Will maintain blended guidance for 
the time being until there's more agreement, but for now will 
continue to reassess subsequent guidance. 

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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. Winds currently shifting NE and diminishing to near 10 kts
as the high pressure system takes over. Winds shift SE this 
evening, generally around 5 kts, and some higher level clouds 
begin to build in overnight.

Thursday Night...Moderate confidence. 

Becoming MVFR to IFR with -SHRA moving in from west to east 
between 06Z and 12Z. S-SW winds develop with gusts nearing 20 kt
closer to sunrise.

Friday...Moderate confidence.

IFR to LIFR with SHRA. Brief respite from SHRA possible in the 
afternoon hours, though low ceilings continue. Will need to 
monitor for the risk of some embedded TSRA and convective 
features. Gusty S to SW winds up to 30 kt with higher gusts 
possible near the coasts and higher elevations.

KBOS Terminal...High confidence in TAF. 

KBDL Terminal...High confidence in TAF.

Outlook /Saturday through Tuesday/...

Saturday: Mainly VFR, with local MVFR possible. Windy with
gusts up to 30 kt. 

Saturday Night: VFR. Windy with local gusts up to 30 kt. Patchy
frost.

Sunday through Sunday Night: VFR. 

Monday: VFR. Breezy. 

Monday Night through Tuesday: VFR. 

&&

.MARINE...

Forecaster Confidence Levels...

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

Tonight through Saturday...High confidence.

High pressure moves east of the waters tonight...but winds/seas will 
remain below small craft advisory thresholds. Intensifying low 
pressure will move across the eastern Great Lakes tonight and then 
proceed near the northern New England/Quebec border Fri into Fri 
evening. Ahead of this front...strong small craft southerly wind 
gusts along with choppy seas will develop early Fri. We have hoisted 
small craft headlines for all our waters on Fri. 

Behind this cold front...NW wind gusts of 30-35 knots will develop 
especially late Fri night into Sat in the CAA pattern. Given it is 
marginal...we opted to continue Gale Watch over this time period. 
Despite marginal conditions...cold air advection patterns can often 
overperform this time of year given relatively warm SST which can 
enhance mixing. Either way...strong SCA to gale force wind gusts are 
expected with choppy seas. 

Outlook /Saturday night through Tuesday/...

Saturday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Rough seas up to 10 ft. 

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

Sunday Night: Winds less than 25 kt. 

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 AM to 6 PM EDT Friday for ANZ230-
     236.
     Gale Watch from Friday evening through Saturday evening for 
     ANZ230>237-250-251-254>256-280>283.
     Small Craft Advisory from 6 AM to 6 PM EDT Friday for 
     ANZ231>235-237-250-251-254>256.

&&

$$

DISCUSSION...Frank/Loconto
AVIATION...McMinn
MARINE...Frank/Loconto