Special Weather Statement, NWS Boston/Norton, MA

Area Forecast Discussion
National Weather Service Boston/Norton MA
959 PM EDT Wed Aug 8 2018

.SYNOPSIS...

The risk of scattered showers and thunderstorms will continue
into Thursday along with very warm and humid conditions. Weak
high pressure will bring dry conditions on Friday. Waves of low
pressure will move along a stalled front south of New England,
which could bring scattered showers and thunderstorms from time
to time from Friday night through the weekend. Another low may
develop early next week, then slowly move across the region
which may bring scattered showers and thunderstorms.

&&

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

10 pm update...

It has been a rather busy evening with clusters of showers and
thunderstorms across the region. These storms produced
torrential rainfall and pockets of localized flash flooding.
The most recent storms brought significant flooding to the
Stowe, Maynard as well as the Framingham/Natick areas. Much of
that activity has weakened...but still a cluster of storms that
was resulting in very heavy rainfall over a portion of south
central MA.

Uncertainty exists on what exactly happens overnight. We are
watching a cluster of showers and thunderstorms with more
torrential rainfall across southeast NY/western CT. Some
guidance indicates this holds together and works into our
western zones over the next few hours. It is certainly plausible
given Capes remaining between 1000 and 1500 J/KG overnight and
deep layer shear increasing to between 30 and 35 knots. There
are also indications we may see showers and thunderstorms
blossom out of nowhere across the southeast New England coast
toward daybreak. While the shear/low level jet is not off the
charts...appears enough to trigger these typical showers and
thunderstorms with the amount of instability.

Main concern with any storms overnight would be heavy
rainfall/localized flooding given high Pwat airmass in place. We
also can not rule out an isolated strong storm or two given
instability in place.

Low temps mainly in the 70 to 75 degree range and will need to
watch for areas of fog developing overnight.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Thursday...

Mid level trough moves into SNE during the afternoon with
attending frontal boundary shifting to the coastal plain by
evening. MLCAPES 1000-2000 J/kg with increasing mid level lapse
rates moving in from the west as temps aloft cool. Expect more
scattered showers/t-storms which may develop in the morning,
but focus should shift to eastern half New Eng in the afternoon
within axis of best moisture, as drier air moves in from the
west. Deep layer shear a bit stronger Thu, up to 30 kt, so
potential for a few strong to severe storms. Heavy rainfall also
a concern with localized flood threat mainly confined to
eastern New Eng.

Temps should reach well into the 80s again with a few locations
possibly around 90 in eastern MA and RI. Dewpoints will be in
the lower 70s, but dropping in the west in the afternoon. Heat
indices may reach mid 90s for a few hours across portions of RI
and eastern MA. Will have to monitor for another heat advisory
for eastern New Eng Thu.

Thursday night...

Cold front moves off the coast with drier air moving into the
region with NW flow. A quiet night expected with cooler and
less humid conditions. Lows will range through the 60s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Overview...
A broad H5 trough crosses New England on Friday with a brief
dry spell with a W-NW flow in place. High amplitude H5 ridge
across the northern Plains into central Canada will allow
trough to develop from New England into the Ohio Valley. Models
and ensembles continue to signal H5 cutoff low from the central
Great Lakes to Ohio valley. In the meantime, noting mid level
ridging shifting westward from the central Atlantic to N and
NE of the Bahamas. This may cause some warmer and possibly
drier conditions around the Mon-Wed timeframe. However, there
is uncertainty due to the movement of the cutoff low into the
central and northern Appalachians by the middle of next week,
Models signaling surface low pressure development and slow
movement across the region that may bring scattered
showers/thunderstorms.

Details...

Friday...
Expect dry conditions as a bubble of high pressure sits across
northern New England into NY state. Dewpts start out in the 60s
early Friday, then gradually fall during the afternoon as the
high tries to nose S. Temps will still be warm, topping off in
the 80s, but the humidity will be lower so it will feel more
comfortable.

Friday night through Sunday...
With the front stalled S of Long Island, weak waves of low pres
will move along it. Clouds develop Fri night, but precip should
hold off across S coastal areas until after midnight. Some
question as to position of this front, and how far N the precip
will develop.

At this point, have carried slight chance POPs Fri evening
mainly S of the Mass Pike, then POPs increase to chance a bit
further N overnight into Saturday and continue through the
weekend as the front waves along the S coast. Noting marginal
instability, though somewhat higher near or just N of the
front, mainly along the S coast. Can not rule out isolated
thunderstorms at any time. Also noting PWATs at 1.9 to 2
inches, with the higher values along the S coast, so may see
heavy downpours.

Monday through Wednesday...
Models all signal low pres developing across the mid Atlc
states and moving slowly NE. Timing and track are still
somewhat in question as the H5 cutoff low opens up and drifts E
out of NY state. Looks like a better chance of showers/
thunderstorms as the H5 trough shifts E into New England while
slowly flattening. Higher PWATs also surge NE with 2 to 2.2
inches moves to the S coast by 06Z Tue, then most of the region
by 12Z Tue. So, could also see heavy downpours and localized
street/poor drainage flooding in any precipitation Tue into Tue
evening.

May see drier air work in later Tue night into Wed as the mid
level trough shifts NE. May see a few leftover showers lingering
across the interior on Wed.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...

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

Short Term /through Thursday Night/...

Tonight...Moderate confidence.
Scattered showers and thunderstorms, particularly this evening
across the interior, but more scattered showers and isolated
t-storms may move into the region overnight. Mainly VFR outside
of any showers/t-storms. Areas of IFR stratus and fog
developing along the south coast and especially on Cape Cod and
the islands. Patchy late night fog may also develop across
interior locations.

Thursday...Moderate confidence.
Coastal stratus and patchy fog will improve to VFR by midday.
Otherwise, expect scattered showers/t-storms again with activity
shifting to eastern half New Eng during the afternoon as drier
air begins to move in form the west.

Thursday night...Moderate confidence. Mainly VFR.

KBOS Terminal...Moderate confidence in TAF.

KBDL Terminal...Moderate confidence in TAF.

Outlook /Friday through Monday/...

Friday: VFR.

Friday Night: VFR. Slight chance SHRA.

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

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

Sunday: Mainly VFR, with local MVFR possible. Chance SHRA,
slight chance TSRA.

Sunday Night: Mainly IFR, with areas VFR possible. Slight
chance SHRA, patchy BR.

Monday: Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Thursday Night/...High confidence.

Persistent southwest flow through Thu with gusts to 20 kt at
times over nearshore south coastal waters during the
afternoons. Winds shift to W/NW Thu night. Seas mainly 3 ft or
less through Thu night. Vsbys reduced in areas of fog across
south coastal waters tonight into Thu morning. A few t-storms
possible over eastern MA waters into this evening, and all
waters during Thu.

Outlook /Friday through Monday/...

Friday: Winds less than 25 kt.

Friday Night: Winds less than 25 kt. Slight chance of rain
showers. Local visibility 1 to 3 nm.

Saturday: Winds less than 25 kt. Chance of rain showers, slight
chance of thunderstorms.

Saturday Night: Winds less than 25 kt. Chance of rain showers,
isolated thunderstorms, patchy fog. Local visibility 1 to 3 nm.

Sunday: Winds less than 25 kt. Slight chance of rain showers,
isolated thunderstorms.

Sunday Night: Winds less than 25 kt. Slight chance of rain
showers. Areas of visibility 1 to 3 nm.

Monday: Winds less than 25 kt. Slight chance of rain showers,
slight chance of thunderstorms.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

SYNOPSIS...KJC/EVT
NEAR TERM...Frank
SHORT TERM...KJC
LONG TERM...EVT
AVIATION...KJC/EVT
MARINE...KJC/EVT

Hazardous Weather Outlook
National Weather Service Boston/Norton MA
604 PM EDT Wed Aug 8 2018

CTZ002>004-MAZ002>024-026-RIZ001>008-092215-
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-
604 PM EDT Wed Aug 8 2018

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

.DAY ONE...Tonight.

A few strong to severe thunderstorms are possible this evening.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

A few strong to severe thunderstorms are possible Thursday. Main
threat would be very localized strong to damaging wind gusts. In
addition, any thunderstorm that develop will be capable of producing
torrential rainfall, resulting a very localized flood threat.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

ANZ230>237-250-251-254>256-092215-
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-
604 PM EDT Wed Aug 8 2018

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...Thursday through Tuesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

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

You can follow us on Facebook at
www.facebook.com/NWSBoston

You can follow us on Twitter at
@NWSBoston

Special Weather Statement
National Weather Service Boston/Norton MA
1124 PM EDT WED AUG 8 2018

MAZ002-003-008>011-090415-
Western Franklin MA-Western Hampshire MA-Western Hampden MA-
Eastern Hampden MA-Eastern Franklin MA-Eastern Hampshire MA-
1124 PM EDT WED AUG 8 2018

...TORRENTIAL RAINFALL ...

At 1123 PM EDT, Doppler radar was tracking a strong thunderstorm over
Williamsburg, or near Northampton, moving northeast at 20 mph.

Heavy rain with minor flooding as well as winds in excess of 30 mph
will accompany this storm.

Locations impacted include...
Holyoke, Northampton, Deerfield, Easthampton, Montague, Southampton,
Hadley, Sunderland, Hatfield, Williamsburg, Huntington, Conway,
Leverett, Ashfield, Westhampton, Whately, Chester, Chesterfield,
Worthington and Goshen.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4230 7300 4255 7285 4252 7249 4220 7266
      4225 7300
TIME...MOT...LOC 0323Z 224DEG 19KT 4239 7276

md

Special Weather Statement
National Weather Service Boston/Norton MA
1136 PM EDT WED AUG 8 2018

MAZ003-004-090415-
Northern Worcester MA-Eastern Franklin MA-
1136 PM EDT WED AUG 8 2018

...STRONG THUNDERSTORM...

At 1135 PM EDT, Doppler radar was tracking a strong thunderstorm over
Montague, or near Greenfield, moving northeast at 25 mph.

Wind gusts up to 50 mph will accompany this storm.

Locations impacted include...
Greenfield, Orange, Gardner, Athol, Winchendon, Montague, Templeton,
Northfield, Fitzwilliam, Bernardston, Leverett, Erving, Shutesbury,
Phillipston, Gill, Royalston, Petersham, Richmond, 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.

&&

LAT...LON 4272 7229 4272 7210 4253 7201 4247 7251
      4266 7257 4273 7231
TIME...MOT...LOC 0335Z 246DEG 23KT 4256 7249

md

Special Weather Statement
National Weather Service Boston/Norton MA
1157 PM EDT WED AUG 8 2018

CTZ002-MAZ009-011-090445-
Hartford CT-Western Hampden MA-Eastern Hampden MA-
1157 PM EDT WED AUG 8 2018

...TORRENTIAL RAINFALL ...

At 1157 PM EDT, Doppler radar was tracking a thunderstorm over
Burlington, or near Bristol, moving northeast at 45 mph.

Heavy rain with localized flooding along with winds in excess of 30
mph will accompany this storm.

Locations impacted include...
West Hartford, Bristol, Enfield, Southington, Windsor, Agawam,
Farmington, Wolcott, Simsbury, Bloomfield, Avon, Plainville,
Longmeadow, Suffield, East Longmeadow, Windsor Locks, Granby, Canton,
Southwick and Burlington.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4205 7298 4205 7251 4162 7293 4164 7294
      4164 7298 4180 7302 4181 7295 4184 7294
      4185 7295 4188 7295 4189 7294 4190 7291
      4197 7289 4197 7303
TIME...MOT...LOC 0357Z 225DEG 40KT 4177 7300

md

Special Weather Statement
National Weather Service Boston/Norton MA
134 AM EDT THU AUG 9 2018

CTZ004-090600-
Windham CT-
134 AM EDT THU AUG 9 2018

...STRONG THUNDERSTORM...

At 133 AM EDT, Doppler radar was tracking a strong thunderstorm near
Scotland, or near Windham, moving northeast at 45 mph.

Winds in excess of 40 mph will accompany this storm.

Locations impacted include...
Windham, Plainfield, Willimantic, Killingly, Southbridge, Griswold,
Putnam, Thompson, Brooklyn, Woodstock, Willington, Canterbury,
Lisbon, Ashford, Pomfret, Sterling, Chaplin, Hampton, Eastford and
Scotland.

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.

&&

LAT...LON 4166 7209 4172 7223 4173 7219 4175 7218
      4175 7216 4183 7216 4184 7222 4189 7222
      4196 7219 4196 7210 4203 7210 4202 7180
      4171 7179 4164 7188 4163 7196
TIME...MOT...LOC 0533Z 227DEG 38KT 4173 7207

md

Special Weather Statement
National Weather Service Boston/Norton MA
158 AM EDT THU AUG 9 2018

CTZ004-MAZ005-012-013-017-RIZ001-090700-
Windham CT-Southern Worcester MA-Northern Bristol MA-
Western Norfolk MA-Central Middlesex County MA-
Northwest Providence RI-
158 AM EDT THU AUG 9 2018

...STRONG THUNDERSTORM...

At 158 AM EDT, Doppler radar was tracking a strong thunderstorm near
Brooklyn, or 8 miles north of Plainfield, moving northeast at 30 mph.

Wind gusts up to 50 mph will accompany this storm.

Locations impacted include...
Woonsocket, Cumberland, Franklin, North Attleborough, Milford,
Plainfield, Smithfield, Lincoln, Killingly, Webster, Bellingham,
Burrillville, Northbridge, Hopkinton, Uxbridge, North Smithfield,
Wrentham, Scituate, Glocester and Putnam.

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.

&&

LAT...LON 4174 7193 4192 7200 4221 7155 4194 7136
TIME...MOT...LOC 0558Z 229DEG 26KT 4182 7191

mld

Special Weather Statement
National Weather Service Boston/Norton MA
229 AM EDT THU AUG 9 2018

CTZ004-RIZ001>004-090700-
Windham CT-Northwest Providence RI-Eastern Kent RI-Western Kent RI-
Southeast Providence RI-
229 AM EDT THU AUG 9 2018

...STRONG THUNDERSTORM...

At 229 AM EDT, Doppler radar was tracking a strong thunderstorm over
Sterling, or near Plainfield, moving northeast at 25 mph.

Winds in excess of 40 mph will accompany this storm.

Locations impacted include...
Providence, Warwick, Cranston, Coventry, North Providence, West
Warwick, Johnston, Plainfield, Smithfield, Lincoln, Killingly,
Scituate, West Greenwich, Canterbury, Foster, Sterling and Voluntown.

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.

&&

LAT...LON 4164 7179 4164 7189 4174 7194 4190 7147
      4171 7138 4160 7179
TIME...MOT...LOC 0629Z 241DEG 22KT 4173 7181

md