Severe Thunderstorm Warning 126, NWS Boston/Norton, MA

322 
WWUS51 KBOX 242113
SVSBOX

Severe Weather Statement
National Weather Service Boston/Norton MA
513 PM EDT Mon Aug 24 2020

CTC003-013-242122-
/O.CAN.KBOX.SV.W.0126.000000T0000Z-200824T2145Z/
Tolland CT-Hartford CT-
513 PM EDT Mon Aug 24 2020

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN TOLLAND AND
CENTRAL HARTFORD COUNTIES 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. However heavy rain is 
still occurring with this thunderstorm. If you encounter flooded 
roadways, turn around, don't drown. 

LAT...LON 4180 7296 4182 7294 4184 7294 4185 7295
      4189 7294 4190 7291 4195 7290 4203 7263
      4202 7259 4204 7248 4173 7239 4172 7297
      4180 7297
TIME...MOT...LOC 2109Z 250DEG 14KT 4190 7274 

$$

Chai

Area Forecast Discussion
National Weather Service Boston/Norton MA
429 PM EDT Mon Aug 24 2020

.SYNOPSIS...

Scattered showers and thunderstorms will come to an end early
this evening. However, another round of scattered showers and
thunderstorms are expected Tuesday into early Tuesday evening
with an approaching cold front. Much drier and cooler weather
will give a taste of fall to the region later Tuesday night into
Wednesday. Unsettled and warm/muggy weather does return to wrap up the
week and kick-off the weekend.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...

430 PM Update...

* Scattered strong-severe thunderstorms into early evening

Scattered strong to severe thunderstorms were in progress across
the region. SPC Meso-Analysis is indicating around 3000 J/KG of
Cape across southern New England. Despite marginal effective
shear of 25 knots, the amount of instability will be enough to
trigger scattered strong to severe thunderstorms into early this
evening. A contributing factor to this was modest mid level
lapse rates on the order of 6 C/KM to even a bit higher.

The main threat will be localized damaging wind gusts given
DCape values on the order of 1000 J/KG. However, given modest
mid level lapse rates and a lot of instability the risk exists
for isolated reports of large hail. Lastly, slow moving storms
will be capable of producing heavy rain and localized urban
street flooding.

Most of this activity should be winding down by 7 or 8 pm this
evening with the loss of daytime heating. Otherwise, dry weather
expected later this evening into the overnight hours. We will
have to watch for the formation of patchy dense ground fog in
the typically prone locations given light winds and relatively
high dewpoints. This is especially true in locations that
receive localized heavy rainfall from the earlier convection.
Low temperatures will only drop into the middle 60s to the lower
70s and it will be bit humid.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...

Tuesday...

The main concern will revolve around the severe weather
potential Tuesday afternoon into early evening and there are
mixed signals. Plenty of sunshine and westerly flow should push
highs into the upper 80s to the lower 90s by early afternoon.

In regards to the severe weather threat Tuesday afternoon, the
environment will be quite different than what we have see the
past few days. Strong northern stream shortwave energy will
result in jet dynamics increasing significantly during the
afternoon. This should allow bulk effective shear to increase to
between 30 and 40 knots. In addition, modest mid level lapse
rates near 6.5 C/KM along with Capes on the order of 1500 to
2500 J/KG.

The parameters mentioned above are a lot more favorable for
severe weather than what we have seen the past few days. That
being said, there are some potential red flags as well. Westerly
flow aloft may result in too much mid level dry air. This could
potentially could cutoff thunderstorm updrafts. In addition,
westerly flow at the surface will limit surface convergence as
well.

So in a nutshell...the risk certainly exists for a few severe
thunderstorms Tuesday afternoon and early evening. In fact, if
we are able to maintain modest moisture the risk for a localized
microburst or golf ball size hail would be enhanced. This is
because of modest mid level lapse rates and effective bulk
shear. However, if too much mid level dry air overwhelms the
updrafts we may escape with little if any severe weather. We
need to play this somewhat probabilistic. Perhaps the greatest
risk ends up across eastern MA/RI, where better
instability/moisture may persist longer.

Tuesday night...

Any left over convection will dissipate early Tuesday evening.
Otherwise, much drier and cooler weather will follow. 850T drop
to between +8C to +10C by 12z Wednesday. Expect low temps will
bottom out mainly in the 50s to lower 60s by daybreak with a bit
of a northwest breeze on the coast. Dewpoints may be down into
the 40s in many locations as well, so a big change in the
current airmass is on the way.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...

Highlights

* Small Craft Advisory continues through Wednesday morning for the
  outer waters for wave heights 5 & 7 feet.

* Fall-like conditions Wednesday! Sunny, cool, and dry.

* Unsettled with showers and storms late-week through first half of
  upcoming weekend.

Wednesday...

An area of high pres will move south out of Hudson Bay in Canada
early to mid morning Wednesday, bringing big changes to our forecast,
even if it's for a short period of time. A northwest flow will allow
for CAA, temperatures in and around the northern Hudson Bay are
between +8C and +10C. Needless to say, it will feel as if it were
early fall. Guidance is in fairly good agreement that our
temperatures will only reach the low and middle 70s. A few outliers
would be the southern CT River Valley, there temperatures could
reach the upper 70s. And the east slopes of the Berkshires, there
temperatures could possibly top out in the upper 60s.

Otherwise, high pres gives us an abundance of sunshine. A northwest
wind between 10 to 15 mph, and gust to 20 mph, will likely make it
feel a tad bit cooler.

Thursday...

Clouds and showers return, once again, as a weak area of low pres
moves out of the Great Lakes region. As previously stated on Sunday,
the ECMWF and GFS have had differences in regards to the timing of
the rains arrival. Still, the GFS is on the slower side, while the
ECMWF is a couple of hours quicker... we went ahead and increased
POPs during the afternoon and evening hours. Temperatures wise,
afternoon maximum temperatures will be a tad warmer as our wind
direction becomes southwesterly.

Friday through Sunday...

Heading into Friday and the start of the weekend the forecast
remains unsettled. Though there is a toss-up between the models for
what we can expect. On Friday, the EMCWF keeps southern New England
dry while GFS is on the wet side. The Super Blend is indicating that
the GFS could be the better solution, we did opt to go with chance
showers and thunderstorms. Then, what might be the leftovers of
Laura could be enroute to southern New England by Saturday and
moving off the east coast by in time to give us a dry Sunday.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

18Z Update...

This Afternoon...Moderate confidence.

Scattered SHRA/TSRA will continue into early this evening. So
while VFR conditions dominate, localized pockets of IFR-LIFR
conditions possible in any strong thunderstorms. Localized
strong wind gusts possible too. Low clouds/fog should mainly be
confined to ACK and parts of the Cape.

Tonight...Moderate confidence.

Scattered SHRA/TSRA should be winding down towards 00z, but can
not rule out a bit of activity lingering an hour or two longer.
Otherwise, VFR much of the evening but patchy ground fog may
develop late in the typically prone locations. Low clouds should
be confined to ACK and perhaps near the south coast and Cape
Cod. Light SW winds.

Tuesday...Moderate confidence.

Patchy ground fog should burnoff by mid morning, yielding mainly
VFR conditions. The main concern will be Tuesday afternoon and
evening with the potential for a few strong thunderstorms. Some
uncertainty on areal coverage, but a few may result in strong
wind gusts.

Tuesday night...High confidence.

Any left over convection should wind down early in the evening.
Otherwise, VFR with NW winds of 5 to 15 knots with some 20 to 25
knot gusts expected across portions of the coastal plain.

KBOS Terminal...Moderate confidence in TAF. Main concern is the
threat for scattered thunderstorms in the vicinity of the
terminal until about 00z.

KBDL Terminal...Moderate confidence in TAF. Main concern is the
threat for scattered thunderstorms in the vicinity of the
terminal until about 00z.

Outlook /Wednesday through Saturday/...

Wednesday: VFR. Breezy.

Wednesday Night: VFR. Breezy. Slight chance SHRA.

Thursday: VFR. Chance SHRA.

Thursday Night: VFR. Slight chance SHRA.

Friday: VFR. Chance SHRA, chance TSRA.

Friday Night: Mainly VFR, with local IFR possible. SHRA likely,
patchy BR.

Saturday: Mainly VFR, with areas IFR possible. SHRA likely,
chance TSRA, patchy BR.

&&

.MARINE...

Tonight...High confidence. Winds/seas remain below SCA
thresholds. SW winds of 5 to 15 knots. Only concern is a few
strong thunderstorms near shore into early this evening and some
fog, which may be locally dense in our southern waters.

Tuesday and Tuesday night...High confidence. WSW wind gusts of
20 to 25 knots expected to develop Tue afternoon, especially in
our southern waters ahead of a cold front. We did begin SCA for
most of our waters during the afternoon, but high confidence
that the develop Tue night. This is when expected NW wind gusts
of 25 to 30 knots develop in the CAA behind the cold front. We
also will have to watch for a few strong thunderstorms Tue
afternoon and early evening with the front itself.

Outlook /Wednesday through Saturday/...

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Areas of seas approaching 5 ft.

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

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

Thursday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers, patchy fog.

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

Friday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Rain showers likely, patchy fog.

Saturday: Winds less than 25 kt. Seas up to 5 ft. Rain showers
likely, chance of thunderstorms, patchy fog.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 2 PM Tuesday to 8 AM EDT Wednesday
     for ANZ231>235-237-251.
     Small Craft Advisory from 2 PM Tuesday to 10 AM EDT Wednesday
     for ANZ250-254>256.

&&

SYNOPSIS...Frank/Gaucher
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...Gaucher
AVIATION...Frank/Gaucher
MARINE...Frank/Gaucher

Hazardous Weather Outlook
National Weather Service Boston/Norton MA
422 PM EDT Mon Aug 24 2020

CTZ002>004-MAZ002>016-026-RIZ001-002-008-252030-
Hartford CT-Tolland CT-Windham CT-Western Franklin MA-
Eastern Franklin MA-Northern Worcester MA-Central Middlesex MA-
Western Essex MA-Eastern Essex MA-Western Hampshire MA-
Western Hampden MA-Eastern Hampshire MA-Eastern Hampden MA-
Southern Worcester MA-Western Norfolk MA-Southeast Middlesex MA-
Suffolk MA-Eastern Norfolk MA-Northern Middlesex MA-
Northwest Providence RI-Southeast Providence RI-Block Island RI-
422 PM EDT Mon Aug 24 2020

This Hazardous Weather Outlook is for northern Connecticut, central
Massachusetts, eastern Massachusetts, northeastern Massachusetts,
western Massachusetts, northern Rhode Island and southern Rhode
Island.

.DAY ONE...Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

ANZ230>237-250-251-254>256-252030-
Boston Harbor-Cape Cod Bay-Nantucket Sound-Vineyard Sound-
Buzzards Bay-Rhode Island Sound-Narragansett Bay-Block Island Sound-
Coastal waters east of Ipswich Bay and the Stellwagen Bank National
Marine Sanctuary-Massachusetts Bay and Ipswich Bay-
Coastal waters from Provincetown MA to Chatham MA to Nantucket MA
out 20 nm-
Coastal Waters extending out to 25 nm South of Marthas Vineyard and
Nantucket-
Coastal Waters from Montauk NY to Marthas Vineyard extending out to
20 nm South of Block Island-
422 PM EDT Mon Aug 24 2020

This Hazardous Weather Outlook is for Massachusetts and Rhode
Island coastal waters.

.DAY ONE...Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

MAZ017>024-RIZ003>007-252030-
Northern Bristol MA-Western Plymouth MA-Eastern Plymouth MA-
Southern Bristol MA-Southern Plymouth MA-Barnstable MA-Dukes MA-
Nantucket MA-Western Kent RI-Eastern Kent RI-Bristol RI-
Washington RI-Newport RI-
422 PM EDT Mon Aug 24 2020

This Hazardous Weather Outlook is for southeastern Massachusetts,
northern Rhode Island and southern Rhode Island.

.DAY ONE...Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

For more information on upcoming hazardous weather, please see the
Area Forecast Discussion on our webpage for the latest forecast
thinking. There is also our Enhanced Hazardous Weather Outlook at
www.weather.gov/box/ehwo

For the latest updates...please visit our webpage at
www.weather.gov/boston

You can follow us on Facebook at
www.facebook.com/us.nationalweatherservice.boston.gov

You can follow us on Twitter at
@NWSBoston

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
330 PM EDT MON AUG 24 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0200 PM     TSTM WND DMG     REHOBOTH                41.83N  71.27W
08/24/2020                   BRISTOL            MA   AMATEUR RADIO

            LARGE TREE FALLING ON WIRES ON OAK STREET.

0235 PM     TSTM WND DMG     REHOBOTH                41.83N  71.27W
08/24/2020                   BRISTOL            MA   AMATEUR RADIO

            UTILITY POLE SNAPPED WITH A TREE DOWN ON THE WIRES ON
            TREMONT ST.

0250 PM     TSTM WND DMG     NORTHFIELD              42.71N  72.44W
08/24/2020                   FRANKLIN           MA   AMATEUR RADIO

            TREE DOWN ON MAIN ST. (ROUTE 63).

0305 PM     TSTM WND DMG     NORTHFIELD              42.71N  72.44W
08/24/2020                   FRANKLIN           MA   AMATEUR RADIO

            MULTIPLE TREES DOWN ON WEST ROAD.

&&

EVENT NUMBER BOX2002006 BOX2002007 BOX2002008 BOX2002009

WS

Special Weather Statement
National Weather Service Boston/Norton MA
330 PM EDT Mon Aug 24 2020

MAZ017-018-020-RIZ005-007-242015-
Southern Bristol MA-Northern Bristol MA-Western Plymouth MA-
Bristol RI-Newport RI-
330 PM EDT Mon Aug 24 2020

...STRONG THUNDERSTORM OVER PARTS OF SOUTHERN RHODE ISLAND AND
MASSACHUSETTS...

At 328 PM EDT, Doppler radar was tracking a strong thunderstorm over
Warren, or near Bristol, moving east at 10 mph.

Penny size hail and winds in excess of 40 mph will accompany this
storm. Torrential rainfall is also occurring with this slow-moving
storm.

Locations impacted include...
Fall River, Dartmouth, Bristol, Somerset, Portsmouth, Barrington,
Swansea, Tiverton, Westport, Seekonk, Rehoboth, Warren, Lakeville,
Freetown, Dighton and Berkley.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Get indoors when this storm approaches. Winds may be strong enough to
produce minor damage, such as a few downed branches.

Do not drive through flooded roads or underpasses. Avoid low lying
areas near small streams.

Frequent lightning was occurring. Lightning can strike far away from
the storm. Go inside a building or vehicle. Wait at least 30 minutes
until after the storm has passed to resume outdoor activities.

&&

LAT...LON 4164 7124 4165 7122 4164 7121 4171 7116
      4172 7120 4171 7121 4173 7122 4170 7124
      4172 7126 4168 7123 4164 7126 4168 7128
      4165 7130 4171 7129 4172 7133 4180 7132
      4179 7109 4181 7099 4159 7102
TIME...MOT...LOC 1928Z 270DEG 7KT 4171 7123

Chai

Special Weather Statement
National Weather Service Boston/Norton MA
337 PM EDT Mon Aug 24 2020

MAZ003-004-010-011-242015-
Eastern Hampden MA-Eastern Franklin MA-Northern Worcester MA-
Eastern Hampshire MA-
337 PM EDT Mon Aug 24 2020

...STRONG THUNDERSTORM OVER EASTERN HAMPSHIRE COUNTY...

At 336 PM EDT, Doppler radar was tracking a strong thunderstorm over
Hadley, or over Amherst, moving east at 10 mph.

Penny size hail and winds in excess of 40 mph will accompany this
storm. Torrential rainfall is also occurring with this storm.

Locations impacted include...
Amherst, Northampton, Ludlow, South Hadley, Belchertown, Palmer,
Ware, Granby, Hadley, Sunderland, Hatfield, Hardwick, Leverett,
Shutesbury, Whately, Pelham, Petersham and New Salem.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Get indoors when this storm approaches. Winds may be strong enough to
produce minor damage, such as a few downed branches.

Do not drive through flooded roads or underpasses. Avoid low lying
areas near small streams.

Frequent lightning was occurring. Lightning can strike far away from
the storm. Go inside a building or vehicle. Wait at least 30 minutes
until after the storm has passed to resume outdoor activities.

&&

LAT...LON 4231 7266 4245 7259 4239 7223 4216 7236
TIME...MOT...LOC 1936Z 290DEG 9KT 4235 7255

Chai

Special Weather Statement
National Weather Service Boston/Norton MA
341 PM EDT Mon Aug 24 2020

MAZ003-004-242045-
Eastern Franklin MA-Northern Worcester MA-
341 PM EDT Mon Aug 24 2020

...STRONG THUNDERSTORM MOVING INTO NORTHERN WORCESTER COUNTY...

At 341 PM EDT, Doppler radar was tracking a strong thunderstorm near
Athol, or near Orange, moving southeast at 20 mph.

Penny size hail and winds in excess of 40 mph will accompany this
storm.

Locations impacted include...
Leominster, Fitchburg, Orange, Gardner, Athol, Winchendon, Lunenburg,
Templeton, Rutland, Westminster, Ashburnham, Barre, Hubbardston,
Princeton, Phillipston, Royalston, Petersham and New Salem.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Get indoors when this storm approaches. Winds may be strong enough to
produce minor damage, such as a few downed branches.

&&

LAT...LON 4255 7230 4271 7220 4259 7175 4237 7199
TIME...MOT...LOC 1941Z 301DEG 15KT 4261 7217

BW

Special Weather Statement
National Weather Service Boston/Norton MA
411 PM EDT Mon Aug 24 2020

MAZ003-004-010-242100-
Eastern Franklin MA-Northern Worcester MA-Eastern Hampshire MA-
411 PM EDT Mon Aug 24 2020

...STRONG THUNDERSTORM OVER EASTERN FRANKLIN COUNTY...

At 409 PM EDT, Doppler radar was tracking a strong thunderstorm over
Leverett, or 8 miles north of Amherst. This storm was nearly
stationary.

Penny size hail and winds in excess of 40 mph will accompany this
storm. Torrential rainfall is also occurring with the storm.

Locations impacted include...
Amherst, Deerfield, Belchertown, Montague, Sunderland, Leverett,
Shutesbury, Pelham, Petersham, New Salem and Wendell.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Get indoors when this storm approaches. Winds may be strong enough to
produce minor damage, such as a few downed branches.

Do not drive through flooded roads or underpasses. Avoid low lying
areas near small streams.

Frequent lightning was occurring. Lightning can strike far away from
the storm. Go inside a building or vehicle. Wait at least 30 minutes
until after the storm has passed to resume outdoor activities.

&&

LAT...LON 4248 7259 4258 7248 4250 7222 4233 7239
TIME...MOT...LOC 2009Z 312DEG 3KT 4248 7247

Chai

Special Weather Statement
National Weather Service Boston/Norton MA
427 PM EDT Mon Aug 24 2020

CTZ002-242115-
Hartford CT-
427 PM EDT Mon Aug 24 2020

...STRONG THUNDERSTORM APPROACHING HARTFORD COUNTY...

At 426 PM EDT, Doppler radar was tracking a strong thunderstorm near
Burlington, or 8 miles east of Torrington, moving east at 10 mph.

Penny size hail and wind gusts up to 50 mph will accompany this
storm. Torrential rainfall is also occurring with this storm.

Locations impacted include...
Hartford, New Britain, West Hartford, Bristol, Newington, Windsor,
Farmington, Simsbury, Bloomfield, Avon, Plainville, Windsor Locks,
Granby, Canton, Burlington and East Granby.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Get indoors when this storm approaches. Winds may be strong enough to
produce minor damage, such as a few downed branches.

Do not drive through flooded roads or underpasses. Avoid low lying
areas near small streams.

Frequent lightning was occurring. Lightning can strike far away from
the storm. Go inside a building or vehicle. Wait at least 30 minutes
until after the storm has passed to resume outdoor activities.

&&

LAT...LON 4181 7295 4184 7294 4185 7295 4189 7294
      4190 7291 4192 7291 4194 7266 4165 7273
      4172 7300 4180 7302
TIME...MOT...LOC 2026Z 285DEG 10KT 4181 7297

Chai