Special Weather Statement, NWS Boston/Norton, MA

Area Forecast Discussion
National Weather Service Boston/Norton MA
352 PM EDT Sat Sep 9 2023

.SYNOPSIS...
Very warm and humid weather will persist this weekend with
showers and thunderstorms at times. Drier and less humid
conditions may arrive Tuesday, but will be short-lived as the
risk for showers and thunderstorms increases again by the end of
next week. Cooler and less humid to end next week. Increasing
waves and dangerous rip currents late week and into next weekend
ahead of Hurricane Lee. Still but our attention turns to
Hurricane Lee. Confidence in any other impacts remains low at
this time. Refer to the latest forecasts on Hurricane Lee from
the National Hurricane Center.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Main focus for showers and thunderstorms this afternoon extended
from northeast CT, across northern RI into SE MA. A stalled
front extended from near Concord NH, to near Orange MA, to near
Windsor Locks CT early this afternoon. Greatest instability
remained to the SE of this front, but almost no effective wind
shear to organize the convection. All sorts of outflow
boundaries evident in the latest radar imagery. Thus storms are
moving in a semi-random fashion as they interact with these
leftover boundaries due to the absence of a stronger steering
flow.

Despite the loss of daytime heating, that stalled front will not
be going anywhere. Still expecting showers and a few
thunderstorms to continue overnight.

Humidity also sticking around, and will keep low temperatures
above normal. There does appear to be a little more support

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Synoptic pattern does not change much Sunday into Sunday night.
Will still be warm and humid with a front stalled across
southern New England. There should be more mid level support
from a modest passing shortwave. Still, not much shear to
organize convection, so the severe weather threat remains low.

More of the same tonight and Sunday as frontal boundary remains
stalled over SNE and we remain in warm and humid airmass. The
high humidity will raise concerns for downpours, and possible
localized flooding. Above normal temperatures continue.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Highlights:

* Warm and muggy conditions continue through mid-week, then
  cooling off with less humidity by late this week.

* Unsettled weather pattern will provide opportunities for
  showers Monday and Wednesday into Thursday. A break from the
  stormy weather by late this week.

* Watching Hurricane Lee, likely to be northeast of the Bahamas
  by Thursday. Then all eyes are where Lee goes as it nears the
  east coast of the CONUS.

Big Picture...

An active period of weather all around, with a day or two of
quieter conditions. In general, no significant deviations to
this portion of the forecast. As mentioned, mid-level heights
fall Monday with the development of a mid-level trough over the
northern Great Lakes. The trough kicks east for
Wednesday/Thursday with a robust shortwave. Friday into Saturday
weak mid-level ridging builds across the eastern third of the
CONUS, this will play an important role in the steering of
Hurricane Lee.

Precipitation...

PWATs fall throughout Monday, ECMWF a bit faster than the GFS,
still the day starts with values above 1.5 inch. Departing
shortwave gives the lift needed for a few heavy showers and
embedded thunder. 12z guidance from the HREF does give a glimmer
of how the morning could unfold. Majority of CAMs do have
widely scattered showers lingering at 12z Monday, where the CAMs
off the HREF end. NAM 3KM continues shower activity into the
afternoon hours. Over all severe threat does appear to be low,
greater threat would be locally heavy downpours leading to minor
flooding issues. WPC kept the area under a marginal risk for
excessive rainfall.

Monday night into Tuesday PWATs fall, slightly, with the
departure of a stationary front. Still the airmass remains warm
and muggy as PWATs are between 1.0 and 1.4 inch. With little to
no forcing, do not expect any shower activity, though it will
likely be on the cloudier side.

Wednesday into early Thursday continues to be the most active
part of this coming week, outside of any potential impacts
Hurricane Lee may have. The deepening mid-level trough and
shortwave approach from the west late Tuesday night into early
Wednesday. Southwest flow advects higher PWATs back into the
region, reaching between 1.5 and 1.8 inches. As for how much
rain, the ensembles have shifted a tad lower of a 30 to 50
percent chance of 1.0 inch of rainfall over a 24 hour period.
The deterministic models have a smattering of 0.75 to 1.50
inches with locally higher amounts. Never the less, WPC does
have our region placed under a Slight Risk for excessive
rainfall. Something we will have to closely watch over the next
couple of days.

Late Thursday into early Friday a refreshing airmass arrives
with PWATs falling to less than 0.5" through at least the first
half of next weekend. Weak mid-level ridging and surface high
pressure should provide fairly quiet conditions Friday into
Saturday. The one caveat, Hurricane Lee. Currently, the track
from NHC maintains Lee as a major hurricane, category three of
greater, this coming Thursday northeast of the Bahamas. If Lee
were to have any impacts it would not come until late next
week/weekend. What is likely are large surf and dangerous rip
currents for area beaches.

Visit nhc.noaa.gov for the latest on Key Messages on Hurricane
Lee.

Temperatures...

Warm and muggy conditions continue early next week with Monday
and Tuesday likely to be the warmest. Afternoon highs are middle
to upper-70s with a few locations across the CT River Valley
and metrowest of Boston hitting 80F. While it will be cooler,
the dewpoints remain rather high, between 68-72 degrees each
day. Essentially, "air you can wear". Overnight lows remain mild
as well due to the southwest flow and cloud cover will only
allow for temperatures to fall between 65-70 degrees. It is not
until mid-week we see a break from the warmth, Wednesday we
transition to slightly cooler temperatures in the low and
middle-70s, still dewpoints are running high between 68-72
degrees. Thursday into Friday dewpoints finally drop into the
comfortable range in the lower-50s! Coupled with seasonable
temperatures in the low-70s into Saturday.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

Moderate Confidence, mainly due to location and timing of
convection.

Wide mix of condition this afternoon and evening, ranging from
VFR to MVFR in heavier showers and thunderstorms. Main focus for
SHRA/TSRA extended from KIJD-KSFZ-KTAN. This placed KBOS along
the northern edge, where it should remain for a few more hours.
Storm movement remained very slow, less than 10 kt.

Should see return of low clouds/fog again later tonight,
followed by improvement again Sunday morning. Thinking the
latest guidance is too aggressive with the really low
conditions. Do think there will be ceilings between 003-010,
but the visibility will be higher than the 1/4 to 1/2 mile at
most locations.

More numerous showers across the interior Sunday afternoon.
Still a risk for thunderstorms.

KBOS TAF...Moderate confidence in TAF.

KBDL TAF...Moderate confidence in TAF.

Outlook /Monday through Thursday/...

Monday: Mainly VFR, with areas MVFR possible. Chance SHRA,
isolated TSRA.

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

Tuesday: Mainly VFR, with local IFR possible. Slight chance
SHRA, isolated TSRA.

Tuesday Night: Mainly VFR, with areas IFR possible. Chance
SHRA, isolated TSRA.

Wednesday: Mainly MVFR, with local IFR possible. SHRA likely,
isolated TSRA.

Wednesday Night: Mainly VFR, with local MVFR possible. Breezy.
SHRA likely, isolated TSRA.

Thursday: VFR. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Weak high pressure east of New England will maintain light S/SW
flow today through Sunday, though local sea breezes are expected
along the east coast after noon. Widely scattered showers/storms
can't be ruled out, but they should be more focused well inland.
Patchy fog develops later tonight before dissipating Sunday
morning.

Outlook /Monday through Thursday/...

Monday: Winds less than 25 kt. Chance of rain showers, isolated
thunderstorms.

Monday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers, isolated thunderstorms.

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

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

Wednesday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers, isolated thunderstorms.

Wednesday Night: Winds less than 25 kt. Seas up to 5 ft. Rain
showers likely, isolated thunderstorms.

Thursday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers.

&&

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

&&

SYNOPSIS...Belk/Dooley
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...Dooley
AVIATION...Belk/Dooley
MARINE...Belk/Dooley

Special Weather Statement
National Weather Service Boston/Norton MA
316 PM EDT Sat Sep 9 2023

MAZ012-013-017-RIZ001-092000-
Southern Worcester MA-Western Norfolk MA-Northern Bristol MA-
Northwest Providence RI-
316 PM EDT Sat Sep 9 2023

...A strong thunderstorm will impact portions of southeastern
Worcester, southwestern Norfolk, northwestern Bristol and
northeastern Providence Counties through 400 PM EDT...

At 316 PM EDT, Doppler radar was tracking a strong thunderstorm over
North Smithfield, or near Woonsocket, moving northeast at 10 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Strong winds could cause minor damage such as downed
         branches. Little to no impact from hail is expected.

Locations impacted include...
Woonsocket, Cumberland, Franklin, North Attleborough, Attleboro,
Mansfield, Smithfield, Lincoln, Foxborough, Bellingham, North
Smithfield, Norfolk, Wrentham, Blackstone, and Plainville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Get indoors when you hear thunder. Do not resume outdoor activities
until at least 30 minutes after the storm has passed.

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

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. For your
safety, go indoors or to your vehicle.

This storm may intensify and become severe. Stay tuned to your local
media for updates and possible warnings.

&&

LAT...LON 4190 7154 4199 7160 4214 7140 4200 7118
TIME...MOT...LOC 1916Z 243DEG 7KT 4195 7154

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

KP

Special Weather Statement
National Weather Service Boston/Norton MA
335 PM EDT Sat Sep 9 2023

MAZ002-003-008-010-092030-
Western Franklin MA-Western Hampshire MA-Eastern Franklin MA-
Eastern Hampshire MA-
335 PM EDT Sat Sep 9 2023

...A strong thunderstorm will impact portions of central Hampshire
and central Franklin Counties through 430 PM EDT...

At 335 PM EDT, Doppler radar was tracking a strong thunderstorm over
Whately, or 9 miles north of Northampton, moving east at 5 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Strong winds could cause minor damage such as downed
         branches. Little to no impact from hail is expected.

Locations impacted include...
Amherst, Greenfield, Deerfield, Montague, Hadley, Sunderland,
Hatfield, Williamsburg, Bernardston, Conway, Shelburne, Leverett,
Shutesbury, Ashfield, Colrain, Gill, Whately, Pelham, Goshen, and
Leyden.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Get indoors when you hear thunder. Do not resume outdoor activities
until at least 30 minutes after the storm has passed.

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

This storm may intensify and become severe. Stay tuned to your local
media for updates and possible warnings.

&&

LAT...LON 4239 7243 4239 7278 4248 7280 4272 7258
TIME...MOT...LOC 1935Z 270DEG 6KT 4246 7267

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

KP

Special Weather Statement
National Weather Service Boston/Norton MA
338 PM EDT Sat Sep 9 2023

CTZ003-004-092045-
Tolland CT-Windham CT-
338 PM EDT Sat Sep 9 2023

...A strong thunderstorm will impact portions of southern Windham and
east central Tolland Counties through 445 PM EDT...

At 338 PM EDT, Doppler radar was tracking a strong thunderstorm over
Windham, moving northeast at 5 mph.

HAZARD...Wind gusts up to 50 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Strong winds could cause minor damage such as downed
         branches. Minor damage to outdoor objects is possible.

Locations impacted include...
Mansfield, Windham, Plainfield, Willimantic, Killingly, Coventry,
Brooklyn, Columbia, Canterbury, Pomfret, Sterling, Chaplin, Hampton,
Eastford, and Scotland.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Get indoors when you hear thunder. Do not resume outdoor activities
until at least 30 minutes after the storm has passed.

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

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. For your
safety, go indoors or to your vehicle.

This storm may intensify and become severe. Stay tuned to your local
media for updates and possible warnings.

&&

LAT...LON 4166 7213 4166 7216 4171 7224 4171 7225
      4175 7228 4192 7198 4168 7181 4164 7198
TIME...MOT...LOC 1938Z 242DEG 6KT 4171 7214

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH

KP

Preliminary Local Storm Report
National Weather Service Boston/Norton MA
347 PM EDT Sat Sep 9 2023

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

0335 PM     Tstm Wnd Dmg     2 NW Mansfield          42.04N 71.24W
09/09/2023                   Norfolk            MA   Law Enforcement

            Tree down on Fisher Street in the town of
            Foxborough. Relayed by amateur radio.

&&

TD

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Special Weather Statement
National Weather Service Boston/Norton MA
404 PM EDT Sat Sep 9 2023

MAZ006-007-014-015-092100-
Eastern Essex MA-Suffolk MA-Western Essex MA-Southeast Middlesex MA-
404 PM EDT Sat Sep 9 2023

...A strong thunderstorm will impact portions of southeastern Essex,
north central Suffolk and east central Middlesex Counties through 500
PM EDT...

At 403 PM EDT, Doppler radar was tracking a strong thunderstorm over
Saugus, moving northeast at 15 mph.

HAZARD...Wind gusts up to 50 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Strong winds could cause minor damage such as downed
         branches. Minor damage to outdoor objects is possible.

Locations impacted include...
Boston, Cambridge, Lynn, Somerville, Malden, Medford, Revere,
Peabody, Arlington, Everett, Salem, Beverly, Woburn, Chelsea,
Gloucester, Melrose, Saugus, Danvers, Wakefield, and Stoneham.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Get indoors when you hear thunder. Do not resume outdoor activities
until at least 30 minutes after the storm has passed.

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

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. For your
safety, go indoors or to your vehicle.

This storm may intensify and become severe. Stay tuned to your local
media for updates and possible warnings.

&&

LAT...LON 4258 7064 4238 7095 4233 7107 4243 7119
      4275 7081
TIME...MOT...LOC 2003Z 233DEG 12KT 4247 7103

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH

KP