Severe Thunderstorm Warning 62, NWS Boston/Norton, MA

519 
WWUS51 KBOX 181120
SVSBOX

Severe Weather Statement
National Weather Service Boston/Norton MA
720 AM EDT Fri Aug 18 2023

CTC003-013-015-181145-
/O.CON.KBOX.SV.W.0062.000000T0000Z-230818T1145Z/
Windham CT-Tolland CT-Hartford CT-
720 AM EDT Fri Aug 18 2023

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 745 AM EDT
FOR SOUTHWESTERN WINDHAM...CENTRAL TOLLAND AND SOUTHEASTERN HARTFORD
COUNTIES...

At 719 AM EDT, a severe thunderstorm was located over Bolton, or near
Vernon, moving northeast at 40 mph.

HAZARD...60 mph wind gusts and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees.

Locations impacted include...
Manchester, East Hartford, Glastonbury, Vernon, Mansfield, Windham,
Willimantic, Tolland, Coventry, Hebron, Marlborough, Willington,
Columbia, Bolton, Ashford, Andover, Chaplin, and Scotland.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4193 7223 4165 7205 4166 7216 4171 7224
      4169 7227 4167 7227 4164 7233 4161 7233
      4159 7239 4160 7241 4158 7246 4165 7251
      4165 7254 4174 7264
TIME...MOT...LOC 1119Z 237DEG 33KT 4177 7241 

TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.88 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$
Dooley

581 
WWUS51 KBOX 181141
SVSBOX

Severe Weather Statement
National Weather Service Boston/Norton MA
741 AM EDT Fri Aug 18 2023

CTC003-013-015-181151-
/O.EXP.KBOX.SV.W.0062.000000T0000Z-230818T1145Z/
Windham CT-Tolland CT-Hartford CT-
741 AM EDT Fri Aug 18 2023

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHWESTERN WINDHAM...CENTRAL
TOLLAND AND SOUTHEASTERN HARTFORD COUNTIES WILL EXPIRE AT 745 AM
EDT...
                
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 will be allowed to expire.  However gusty
winds and heavy rain are still possible with this thunderstorm.

LAT...LON 4193 7223 4165 7205 4166 7216 4171 7224
      4169 7227 4167 7227 4164 7233 4161 7233
      4159 7239 4160 7241 4158 7246 4165 7251
      4165 7254 4174 7264
TIME...MOT...LOC 1141Z 247DEG 28KT 4183 7221 

$$
Dooley

Area Forecast Discussion
National Weather Service Boston/Norton MA
343 AM EDT Fri Aug 18 2023

.SYNOPSIS...
Showers and thunderstorms overspread southern New England after
sunrise Friday, with a warm front in the morning followed by cold
front approaching from the west during the afternoon. A few of the
storms may become severe and also produce brief torrential rainfall
and localized flooding. Then dry, less humid weather overspreads the
area Friday night, with some sunshine finally returning Saturday.
Turning warmer and more humid Sunday into Monday. The next chance
for showers and thunderstorms arrives sometime late Monday into
Monday night. Turning slightly cooler and drier through the middle
of next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

345 AM update...

Key Points...

* Showers & t-storms after sunrise into this afternoon, with a few
  of which may become severe but not expecting a widespread outbreak

* Brief torrential rainfall may result in localized street flooding

* Any lingering showers & storms come to an end toward sunset, with
  cooler/less humid weather Fri night

Friday...

Latest water vapor imagery shows a high amplitude, negative tilt
trough moving across the eastern Great Lakes into NYS, providing
strong forcing for ascent and resulting in a squall line of
convection from eastern PA and eastern NY at 3 AM. This line of
convection will interact with a warm front lifting northward into
SNE this morning. As warm sector overspreads SNE this morning, dew
pts will surge into the low and mid 70s, along with PWATs climbing
to 1.5 to 2.o inches. This very humid airmass combined with strong
forcing for ascent from the approaching negatively tilted trough,
will result in brief torrential downpours. HREF offers low probs of
1-2 inches of rain in a short period of time. This may result in
localized flooding. However, storms will be moving rapidly, 40-50
mph to the northeast and this will likely limit the flood potential.
Rainfall across the region will range from 0.50 to 1.0 inches, but
up to 2 inches in heavier bands and thunderstorms.

These strong wind fields aloft, combined with ML CAPES on the order
of 750-1500 j/kg, in response to dew pts surging into the low and
mid 70s, and highs warming into the low 80s, will yield a wind
threat from the stronger thunderstorms. HREF indicates modest
updraft helicity swaths this morning and again this afternoon. There
could also be a few rotating storms in vicinity of the warm front
this morning, especially if a meso-low develops, which will enhance
low level helocity. This will need to be watched. Then a second
round of showers and thunderstorms this afternoon with the
approaching cold front and dry slot. Given the progressive flow
aloft, storms will exit offshore between 5 pm and 8 pm.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...

345 AM update...

* Drier and much less humid with cooler temps

Friday night...

Post frontal airmass overspreads the region with dew pts crashing
into the 50s and PWATs down to about 0.75 inches! Hence, much drier
and less humid.  West winds 5 to 15 mph. Overnight lows in the 50s.

Saturday...

Dry weather with morning sunshine giving way to diurnal afternoon
clouds given chilly (-12C at 500 mb) cyclonic flow aloft. This will
result in slightly cooler than normal temps, with highs only in the
low to mid 70s. Low humidity with dew pts in the 50s and a west
breeze 10-15 mph.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...

345 AM

Highlights...

* Dry to end the weekend and much of next week with continued
  seasonable temperatures.

* Next chance for unsettled weather comes late Monday but
  widespread/heavy rain is not expected.

Details...

The extended forecast looks quiet overall with a few chances of
unsettled weather on Monday and perhaps again late week. At the
synoptic scale we'll have a broad mid level ridge over the center of
the country with SNE sandwiched between itself and the trough of low
pressure over eastern Canada. At the surface high pressure centered
south of the region builds north and remains in control for most of
the period. The exception is Monday when a lobe of northern stream
energy rounds the base of the trough while its surface trough
reflection crosses New England at the same time. After a sunny and
dry Sunday this brings increasing cloudcover and the chance for
widely scattered showers with potential for embedded thunder.
Humidity increases ahead of the cold front with dewpoints rising to
the upper 60s Monday before dropping back into the 40s/50s on
Tuesday. After Monday high pressure moves in from the Great Lakes
keeping things dry. Temperature-wise Monday will be the warmest day
of the extended forecast, in the mid to upper 80s ahead of the cold
front, dropping back into the 70s post frontal for mid week.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

06z update...

Thru 12z Friday...Moderate Confidence.

IFR/LIFR in patchy fog and areas of drizzle. E-NE becoming SE.
Line of thunderstorms across eastern PA/NY at 06z, enters
western MA/CT towards 12z.

After 12z Friday...Moderate Confidence.

IFR/LIFR at 12z lifts to IFR/MVFR midday then MVFR/VFR by toward
sunset. Numerous showers and thunderstorms 12z-18z from west to
east. A few severe storms possible with strong winds and brief
torrential downpours. This activity is associated with a warm
front moving through the region. A cold front moves through
this afternoon, accompanied by scattered showers and
thunderstorms, but likely less intense than morning activity.
The front will be accompanied by a wind shift from SSW to west.
Improving weather with the wind shift.

Friday night...High Confidence.

At 00z any lingering MVFR conditions across Cape Cod and the
Islands will depart early in the evening. Otherwise, VFR
conditions with west winds 10 to 15 knots.

Saturday...high confidence.

Dry weather with SKC in the morning, then VFR cloud bases in the
afternoon. West winds 10 to 20 kt.

KBOS TAF...High confidence in trends. Lower confidence in exact
timing. Thunderstorms move across the terminal 14z-17z with
gusty winds and brief torrential downpours.

KBDL TAF...High confidence in trends. Lower confidence in exact
timing. Thunderstorms move across the terminal 11z-14z with
gusty winds and brief torrential downpours.

Outlook /Saturday Night through Tuesday/...

Saturday Night through Sunday Night: VFR.

Monday: VFR. Slight chance SHRA.

Monday Night through Tuesday: VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

345 AM update...

Friday...high confidence on trends, lower on exact timing.

Warm front lifts north across the RI and MA waters, with predawn SE
winds becoming SSW later this morning at 15-20 kt with a few gusts
up to 25 kt possible. Showers and thunderstorms with brief
torrential rain and gusty winds. Vsby at or below 1 mile in patchy
dense fog before daybreak, then improving to 1-3 miles.

Friday night...high confidence.

A cold front sweeps across the waters Friday evening, with a wind
shift from SSW to west. The front may have a few lingering showers
or thunderstorms early, then improving weather with the wind shift.

Saturday...high confidence.

Dry weather, good vsby and west winds 10-15 kt.

Outlook /Saturday Night through Tuesday/...

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

Sunday through 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.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from noon today to 4 AM EDT Saturday for
     ANZ235-237.
     Small Craft Advisory from 7 AM this morning to 8 AM EDT
     Saturday for ANZ254>256.

&&

SYNOPSIS...Nocera/BW
NEAR TERM...Nocera
SHORT TERM...Nocera
LONG TERM...BW
AVIATION...Nocera/BW
MARINE...Nocera/BW

Hazardous Weather Outlook
National Weather Service Boston/Norton MA
410 AM EDT Fri Aug 18 2023

CTZ002>004-MAZ002>024-026-RIZ001>008-190815-
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 Bristol MA-
Western Plymouth MA-Eastern Plymouth MA-Southern Bristol MA-
Southern Plymouth MA-Barnstable MA-Dukes MA-Nantucket MA-
Northern Middlesex MA-Northwest Providence RI-
Southeast Providence RI-Western Kent RI-Eastern Kent RI-Bristol RI-
Washington RI-Newport RI-Block Island RI-
410 AM EDT Fri Aug 18 2023

This Hazardous Weather Outlook is for northern Connecticut, all of
Massachusetts east of Berkshire County, and Rhode Island.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

ANZ230>237-250-251-254>256-190815-
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-
410 AM EDT Fri Aug 18 2023

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

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

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

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