Special Weather Statement, NWS Boston/Norton, MA

Area Forecast Discussion
National Weather Service Boston/Norton MA
350 PM EDT Sun Jun 28 2020

.SYNOPSIS...
A broad area of low pressure aloft will move over New England
through midweek with another disturbance toward the end of the
week. This will result in an unsettled pattern for the upcoming
week with scattered showers and thunderstorms at times, but a
washout is not expected. Warm and dry weather is expected for
next weekend.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Severe Thunderstorm Watch 312 in effect until 8 pm. Rather
unstable environment across SNE with MLCAPES 2000 J/kg, with
effective bulk shear near 30 kt which is more than enough for
organization and multicellular clusters. Expect scattered
storms to continue to develop through the rest of the afternoon
into early evening as mid level shortwave sweeps through. Most
of the activity has been focused near and north of the Mass
Pike as southerly wind maintaining a stabilizing influence near
the south coast with barely any cu there. Scattered strong
storms possible further south across northern CT, N RI and
interior SE MA within main instability axis, especially along
any outflow boundaries.

Expect convection to gradually diminish this evening as
boundary layer cooling commences. However, with mid level low
dropping south into New Eng, scattered showers and a risk of an
isolated t-storm will continue overnight. Otherwise, expect
stratus and patchy fog to develop along the coast and spread
inland tonight. Lows mostly mid/upper 60s.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Monday into Monday night.

Mid level low and associated cold pool moves south across SNE
during Mon/Mon night. Steepening mid level lapse rates under the
cold pool will result in 1000-2000 J/kg CAPE developing and
expect another round of scattered showers and thunderstorms
during the afternoon/evening. Wind field is weakening as the
upper low moves overhead so not expecting organized storms with
mainly pulse storm mode. Still can't rule out an isolated strong
storm with hail given colder air aloft. Cooler day on Mon,
especially in northern and eastern MA as N/NE wind develops in
response to weak low pres near the south coast. Highs in the 70s
here with 80-85 in the lower CT valley.

Any scattered showers/t-storms will diminish during the
evening, but can't rule out a brief shower/t-storm through the
night with upper low overhead. Lows Mon night in the 60s.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Highlights

* Scattered to isolated diurnal shower and thunderstorm chances
  through midweek. Cooler than normal Tuesday, but some
  uncertainty on temperatures Wednesday.

* Drier late in the week into next weekend.

Monday night through Wednesday night...

Omega block remains in place through at least the middle of the
week. The ridge axis associated with the block extends roughly
from the Southeastern US through the central Great Lakes and
into northern Ontario. New England will have an upper low
rotating over the region throughout this period.

Expect daily shower and thunderstorm activity due to the upper
low overhead. This will keep a -10 to -15 degree Celsius cold
pool overhead at 500 hPa. The combination of the cold pool aloft
with diurnal heating will result in scattered to isolated
shower and thunderstorm activity. There is weak shear, generally
25 kts or less, within the 0-6 km layer during this timeframe,
so storms will remain pulse like. This will result in many areas
remaining dry, but there is 1 to 1.5 inches of PWATs in place.
This could bring heavy rain in areas where showers/storms
develop. Storms may be a bit more robust on Tuesday in
comparison to Wednesday as mid level lapse rates are more
supportive of stronger updrafts based on the GFS/NAM. The
ECWMF/GEM guidance is not in line with the better mid level
lapse rates on either day, so will need to keep an eye on things
Tuesday. MUCAPE values range from a few hundred J/kg closer to
the coast to 1500 J/kg in the interior.

Tapered down precipitation chances during the night time hours
and removed thunder chances after 06Z. The majority of the EPS
members show little to no precipitation, but hard to remove
precip chances completely with the upper low overhead. If there
are any lingering showers leftover they will be diminishing and
should be fairly light.

Temperatures will be cooler than normal with onshore flow
expected Monday night through Tuesday night. There is some
uncertainty between the GFS and the ECMWF/GEM. The GFS keeps the
onshore flow, while the ECMWF/GEM shifts flow to a southerly
and westerly direction at 925 hPa. This appears to be a result
of the upper low center rotating into northern New England with
the ECWMF/GEM, whereas the GFS keeps it overhead. Due to the
differences have stuck with the NBM guidance for temperatures.
This keeps highs in the 70s across the region on Tuesday and
Wednesday. There may be a few 80 degree readings across the CT
River Valley.

Thursday through Saturday...

Upper low begins to breakdown as a jet digs from eastern
Nunavut/northern Quebec and pushes the low offshore on Thursday.
The upper low becomes a trough that digs offshore late on
Thursday. Will still see the diurnal shower/storm chances on
Thursday, but activity should be less widespread with the trough
moving out.

Start to see some differences amongst guidance for late in the
week and into the weekend. A trough digs in from Quebec into
northern New England on Friday. There are some timing and
strength differences amongst guidance with the trough digging
in. Will potentially see the ridge axis build into Quebec and
the eastern Great Lakes, but this is dependent on the guidance.
The GFS does this whereas the ECMWF/GEM keep the ridge in place
over Ontario. Due to the differences this far out have kept the
NBM guidance. This keeps the region drier with mild temperatures
on Thursday, but a return to cooler than normal readings Friday
through Saturday.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

Through 00z...
Mainly VFR cigs, but sct t-storms with brief IFR, heavy rain and
gusty winds, mainly away from south coast.

Tonight...Moderate confidence.
Sct showers and t-storms will dissipate this evening, but
additional showers are possible overnight across eastern New
Eng. Stratus and patchy fog with IFR/LIFR conditions expected
to spread inland from the coast and will likely cover much of
the region east of CT valley by late tonight.

Monday...Moderate confidence.
MVFR/IFR cigs slowly improving to VFR in the afternoon, but MVFR
cigs likely persisting across eastern MA. Scattered showers and
t-storms developing.

Monday night...Moderate confidence.
IFR stratus and patchy fog expected to redevelop but areal
extent is uncertain. Chance showers.

KBOS Terminal...Moderate confidence. Another round of t-storms
possible later this afternoon. IFR stratus and patchy fog
likely developing tonight.

KBDL Terminal...Moderate confidence.

Outlook /Tuesday through Friday/...

Tuesday: Mainly MVFR, with local IFR possible. Chance SHRA.

Tuesday Night: Mainly MVFR, with areas IFR possible. Chance
SHRA.

Wednesday: Mainly MVFR, with local VFR possible. Chance SHRA.

Wednesday Night through Thursday: Mainly VFR, with areas MVFR
possible. Slight chance SHRA.

Thursday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA.

Friday: Mainly VFR, with areas MVFR possible. Chance SHRA.

&&

.MARINE...
Winds and seas will remain below SCA thresholds through Mon
night. Scattered showers/t-storms possible at times.

Outlook /Tuesday through Friday/...

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

Tuesday Night through Wednesday: Winds less than 25 kt. Areas
of seas approaching 5 ft. Slight chance of rain showers.

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

Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers.

Friday: 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...None.

&&

SYNOPSIS...KJC
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...BL
AVIATION...KJC/BL
MARINE...KJC/BL

Hazardous Weather Outlook
National Weather Service Boston/Norton MA
424 PM EDT Sun Jun 28 2020

CTZ002>004-MAZ002>021-026-RIZ001>008-292030-
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-Northern Middlesex MA-Northwest Providence RI-
Southeast Providence RI-Western Kent RI-Eastern Kent RI-Bristol RI-
Washington RI-Newport RI-Block Island RI-
424 PM EDT Sun Jun 28 2020

...SEVERE THUNDERSTORM WATCH 312 IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

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

.DAY ONE...Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Severe Thunderstorm Watch.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

MAZ022>024-292030-
Barnstable MA-Dukes MA-Nantucket MA-
424 PM EDT Sun Jun 28 2020

This Hazardous Weather Outlook is for southeastern Massachusetts.

.DAY ONE...Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

ANZ231>235-250-251-254>256-292030-
Cape Cod Bay-Nantucket Sound-Vineyard Sound-Buzzards Bay-
Rhode 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-
424 PM EDT Sun Jun 28 2020

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

.DAY ONE...Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

ANZ230-236-237-292030-
Boston Harbor-Narragansett Bay-Block Island Sound-
424 PM EDT Sun Jun 28 2020

...SEVERE THUNDERSTORM WATCH 312 IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

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

.DAY ONE...Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Severe Thunderstorm Watch.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

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

Special Weather Statement
National Weather Service Boston/Norton MA
528 PM EDT Sun Jun 28 2020

MAZ024-282230-
Nantucket MA-
528 PM EDT Sun Jun 28 2020

...STRONG THUNDERSTORMS DEVELOPING...

At 528 PM EDT, Doppler radar was tracking a strong thunderstorm over
Nantucket, moving northeast at 30 mph.

Pea size hail and winds in excess of 30 mph will accompany this
storm.

Locations impacted include...
Nantucket.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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 4124 7000 4124 7012 4130 7027 4131 7026
      4128 7021 4129 7020 4130 7010 4128 7009
      4130 7009 4129 7004 4130 7003 4130 7007
      4131 7005 4132 7000 4135 7002 4133 7004
      4134 7004 4139 7005 4129 6997 4126 6996
TIME...MOT...LOC 2128Z 226DEG 25KT 4129 7012

Chai

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