Severe Thunderstorm Warning 9, NWS Boston/Norton, MA

916 
WWUS51 KBOX 192200
SVSBOX

Severe Weather Statement
National Weather Service Boston/Norton MA
600 PM EDT Tue May 19 2026

CTC003-192210-
/O.CAN.KBOX.SV.W.0009.000000T0000Z-260519T2245Z/
Hartford CT-
600 PM EDT Tue May 19 2026

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHERN HARTFORD COUNTY IS
CANCELLED...

The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning has been cancelled.

LAT...LON 4171 7300 4177 7247 4163 7244 4160 7241
      4159 7243 4158 7246 4165 7251 4163 7271
      4160 7272 4155 7282 4157 7283 4155 7286
      4156 7288 4156 7294 4163 7293 4164 7294
      4164 7298
TIME...MOT...LOC 2159Z 263DEG 44KT 4165 7259 

$$

FT

Area Forecast Discussion
National Weather Service Boston/Norton MA
235 PM EDT Tue May 19 2026

.WHAT HAS CHANGED...
No changes were made to this forecast package.

&&

.KEY MESSAGES...

- Lingering thunderstorm activity quickly winds down with the loss
of daytime heating. Expecting very warm minimum temps tonight with
lows in the 60s and low to mid 70s in more urban areas.

- Final day of record warmth Wednesday with highs in the 90s away
from the immediate coast. Chance for strong to severe thunderstorms
by the afternoon with a risk for damaging winds and small hail.

- Cooler temperatures through Memorial Day Weekend.
Unsettled weather returns for the weekend with periods of rain
possible, but confidence is low.

&&

.DISCUSSION...

KEY MESSAGE 1...Lingering thunderstorm activity quickly winds down
with the loss of daytime heating. Expecting very warm minimum temps
tonight with lows in the 60s and low to mid 70s in more urban areas.

Showers and storms are expected to develop across western portions
of our CWA between 3 and 5pm and then quickly move east. Main but
guidance is showing the potential for storms to initiate over the
Southern Adirondacks and Green Mountains and then gradually coalesce
into a more organized line or cluster that generally moves west to
east through the afternoon. Main threats with any organized storms
will be strong to damaging straight-line winds given drier air in
the low to mid-levels resulting in inverted-V soundings. Somewhat
notably, the 12z ALB and OKX soundings featured a modified EML
between 700 and 500mb with mid level lapse rates between 6.5 and 7.5
C/km. Thankfully RAP mesoanalysis indicates limited bulk shear
around 25 kt this afternoon so we're not looking at a widespread
severe weather episode. Still, with CAPE values between 1200 and
1500 J/kg, there could be a severe storm or two north of the Mass
Pike. Activity quickly wanes with the loss of daytime heating this
evening.

Bigger story tonight will be continued heat in humidly. Overnight
lows remain in the upper 60s for much of the region and closer to
the lower and even middle 70s across urban areas. These
temperatures, paired with dewpoints in the 60s will keep apparent
temperatures in the upper 70s to low 80s even well into the night.
Those without adequate access to cooling and air conditioning are at
greatest risk with the elevated overnight lows. There won't be much
in the way of relief from winds as the boundary layer decouples and
winds calm to less than 5 mph for much of the CWA.

KEY MESSAGE 2... Final day of record warmth Wednesday with highs in
the 90s away from the immediate coast. Chance for strong to severe
thunderstorms by the afternoon with a risk for damaging winds and
small hail.

Upper level ridge begins to break down on Wednesday ahead of an
approaching trough. Despite the changes to the upper pattern, 850
temps will remain above +15C S of the Mass Pike and slightly cooler
to the N. Guidance has somewhat increased the speed of the cold
front resulting in increased cloud cover over much of northern
Massachusetts where temperatures have trended a few degrees cooler.
Even in these areas, still think that valley locations see highs in
the low 90s with downsloping from west winds. Further south, there
is higher confidence in more widespread readings in the low to mid
90s away from the water. Greatest chance will be in the HFD PVD and
BOS urban corridor. Dewpoints in the low to mid 60s (discounting the
outlier NAM) will make it feel humid but not tropical by any means.

An approaching cold front provides a much more robust lifting
mechanism on Wednesday. With temperatures quickly warming into the
90s, expecting surface CAPE values to rise to 1000-1500 J/kg. 0-6km
bulk shear values, while fine (25-30 kts), are less favorable for
organized severe weather than they are further north where the
stronger mid level flow resides. So, the ingredients are there for
some strong to severe storms. Wednesday the cold front will serve as
a better lifting mechanism, timed coincident with peak diurnal
heating so would expect more coverage of storms and any storms that
do form have the chance to produce strong to damaging winds
primarily given inverted-v soundings. Greatest threat for any severe
weather will likely be S of the Mass Pike where higher instability
exists.

KEY MESSAGE 3...Cooler and unsettled weather is possible Memorial
Day Weekend, but confidence remains low.

High pressure builds and mid-level ridging building in behind
Wednesday's system bringing near-seasonable temperatures and dry
conditions.

For Memorial Day weekend there is a signal for the pattern to
become more unsettled with a few disturbances moving through
bringing periods of rain. However, there is still a sufficient
amount uncertainty in the details of the track and timing of the
waves which will influence rain chances, timing, and amounts
this holiday weekend. Across deterministic guidance, there is
plenty of spread in the track and details of a system that moves
in from the Ohio Valley. This has led to a range of scenarios
from a drier weekend with seasonable temperatures to a weekend
with periods of rain and cooler temperatures. Whats adds to the
uncertainty is the lack of consistency of models from run to run
as well. From a probabilistic view, ensemble means are keying
in on moderate probabilities for rain across their respective
members at this time, so the risk is there for periods of rain
over the weekend into the holiday. We'll have to keep monitoring
as well get closer and model guidance comes into better
agreement.

&&

.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:

This Afternoon and Tonight...High confidence.

VFR. Sct'd TSRA possible by the afternoon with continued
confidence in impacts between 21 and 00z from BOS, BED, BDL,
and ORH. S-SW wind 10 to 15 kt gusts to 25 kt through the
afternoon and evening. VFR overnight, with MVFR ceilings across
the Cape and Islands. Possible IFR at ACK with areas of fog.

Gusts drop off for terminals not on the Cape and Islands after
00z tonight.

Wednesday...High confidence.

VFR. Scattered TSRA along and ahead of a cold front in the
afternoon and evening. S-SW wind 8-10kt with gusts 20-25 kts
turning NW behind the cold front between 15-00Z. Strong gusts
possible in any thunderstorms.

KBOS...High confidence in TAF.

KBDL...High confidence in TAF.

Outlook /Wednesday through Sunday/...

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

Wednesday Night: VFR. Breezy.

Thursday through Friday: VFR.

Friday Night through Saturday Night: VFR. Chance SHRA.

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.

Small craft advisories remain in effect through 06z Thurs. SW
winds of 15-25 kt continues this afternoon and overnight
Seas will also be building to around 4-6 ft, with some 7
footers possible tonight over the southern waters.

Mainly dry weather prevails through tonight with a few showers
or thunderstorms possible for the northern waters., Some fog may
persist and expand across the southern waters tonight on
increasing southwest winds.

Outlook /Wednesday through Sunday/...

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Local rough seas. Slight chance of rain showers.

Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Chance of rain showers.

Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers.

Thursday Night through Friday: Winds less than 25 kt.

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

Saturday through Saturday Night: Winds less than 25 kt. Seas
locally approaching 5 ft. Chance of rain showers.

Sunday: Winds less than 25 kt. Local rough seas. Chance of rain
showers.

&&

.CLIMATE...
Record Highs for Tue May 19...

BOS 90/2017
BDL 94/1962
PVD 91/2017
ORH 92/1962

Record Highs for Wed May 20...

BOS 91/1996
BDL 99/1996
PVD 95/1996
ORH 91/1903

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT Wednesday for CTZ002>004.
     Air Quality Alert until 11 PM EDT this evening for CTZ003-004.
MA...Heat Advisory until 8 PM EDT Wednesday for MAZ003>007-010>019-
     026.
     Air Quality Alert until 11 PM EDT this evening for MAZ006-007-
     013>019.
RI...Heat Advisory until 8 PM EDT Wednesday for RIZ001>004.
     Air Quality Alert until 11 PM EDT this evening for RIZ001>008.
MARINE...Small Craft Advisory until 2 AM EDT Thursday for ANZ254>256.

&&

DISCUSSION...Mensch/FT
AVIATION...Hrencecin/FT
MARINE...FT
CLIMATE...BW/Hrencecin