Severe Thunderstorm Warning 77, NWS Boston/Norton, MA

679 
WWUS51 KBOX 082133
SVSBOX

Severe Weather Statement
National Weather Service Boston/Norton MA
533 PM EDT Fri Sep 8 2023

MAC011-013-015-082200-
/O.CON.KBOX.SV.W.0077.000000T0000Z-230908T2200Z/
Hampshire MA-Franklin MA-Hampden MA-
533 PM EDT Fri Sep 8 2023

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 600 PM EDT
FOR CENTRAL HAMPSHIRE...CENTRAL FRANKLIN AND NORTH CENTRAL HAMPDEN
COUNTIES...

At 533 PM EDT, a severe thunderstorm was located over Northampton,
moving northeast at 30 mph.

HAZARD...60 mph wind gusts and half dollar size hail.

SOURCE...Radar indicated.

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees.

Locations impacted include...
Holyoke, Amherst, Northampton, Deerfield, South Hadley, Easthampton,
Montague, Hadley, Sunderland, Hatfield, Williamsburg, Leverett,
Shutesbury, Westhampton, Whately, Pelham, and New Salem.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Continuous cloud to ground lightning is occurring with this storm.
Move indoors immediately. Lightning is one of nature's leading
killers. Remember, if you can hear thunder, you are close enough to
be struck by lightning.

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 4225 7264 4231 7276 4257 7258 4244 7232
TIME...MOT...LOC 2133Z 217DEG 25KT 4234 7264 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.25 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

KP

Area Forecast Discussion
National Weather Service Boston/Norton MA
346 PM EDT Fri Sep 8 2023

.SYNOPSIS...

Scattered severe thunderstorms will continue across interior
southern New England this afternoon and evening. Not as hot this
weekend into Monday, but it still will be humid with showers
and thunderstorms at times that may result in locally heavy
rainfall. Somewhat drier and less humid conditions may arrive
around Tuesday, but will be short lived as the risk for showers
and thunderstorms increase by the middle to latter part of next
week. Lastly...Hurricane Lee will spread high surf and dangerous
rip currents to our beaches next week especially by late in the
week.

&&

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

Convection is ongoing and within an extremely favorable
environment. In the area of eastern CT/northern RI/central MA
surface based CAPE is up to 4500 J/kg! This is thanks largely to the
warm, moist airmass. We're looking at temperatures in the mid 80s
and dewpoints in the mid 70s! These storm have a history of
producing 1 inch hail and wind damage. These storms (given low level
lapse rates of 7.5C/km) have exploded from nothing to towering cells
in a very short time. We'll continue to see more of the same, mainly
north and west of the I-95 corridor where the instability is in
closer proximity to the forcing from the approaching trough.
However, can't rule out a few storms making it into eastern MA; with
dewpoints of 74 and 75 at Boston and Marshfield respectively and
steep low level lapse rates if something can make it through the
900mb capping inversion it could take off; low probability but not
zero. Overnight the storms will taper off, but lingering instability
thanks to the heat/humidity (more on that below) may be able to
sustain a few storms overnight. Patchy fog and low clouds return.

Today is the last day we'll deal with heat and humidity that rises
to the level of needing a Heat Advisory, but don't be fooled into
thinking that much cooler and drier air will be arriving. No real
cold front makes it to us and southerly flow continues to offer up
dewpoints in the upper 60s/low 70s. On a related note, low
temperatures will be quite mild once again, in the low 70s.

&&

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

As mentioned above we won't have a dry post frontal airmass to enjoy
on Saturday as the airmass remains largely unchanged. High
temperatures in the mid to upper 80s and dewpoints in the mid 70s
will make for another very muggy day. We'll start off the day with
lots of very low clouds around trapped beneath a 900mb inversion.
This inversion slowly gets mixed out everywhere except the immediate
south coast of RI, Cape Cod, and the islands; these locations could
remain socked much of the day while areas further north/inland will
see a mix of clouds and sun. We'll see instability building once
again, but not as much as today, in the 1000-2500 J/kg range. Bulk
shear will also be less than today and quite unfavorable for
sustained updrafts (10-15kts). Also, the 500 mb jet overhead today
will have moved off to the north. All this, together with the mid
level trough to our west moving extremely slowly will limit our
severe potential tomorrow. SPC currently has SNE under general
thunder with a Marginal Risk (level 1 of 5) just barely clipping our
northwest zones. One concern with these storms may be for localized
flooding, for which WPC has western MA/CT in a marginal risk of
excessive rainfall. While this is a risk given PWATs>1.5", given the
rather dry antecedent conditions unless one area gets a lot of rain
in a storm today and then again tomorrow, flooding is a low
probability. Saturday night will feature more of the same: warm
(upper 60s/low 70s) and muggy. It will be another night with low
clouds and patchy fog thanks to the moist southerly flow.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Key Points...

* Still humid with showers & thunderstorms at times Sun & Mon with
  locally heavy rainfall possible too

* Somewhat lower humidity with seasonable temps Tue but with more
  showers arriving by mid to late next week

* Hurricane Lee will begin to spread high surf & dangerous rip
  currents to our beaches next week...especially late in the week

Details...

Sunday and Monday...

Shortwave trough to our west will continue result in southwest flow
aloft and persistent humidity. Dewpoints of 70+ and Pwats 1.5+
inches coupled with pieces of shortwave energy lifting into southern
New England will result in unsettled weather too with showers and
thunderstorms at times which may result in locally heavy rainfall.
Specific timing remains challenging...but activity is likely to be
most numerous during the afternoon and evenings when diurnal heating
is maximized. The CSU machine learning guidance does indicate some
low probs for excessive rainfall/flooding. This will have to be
watched given 70+ dewpoints and Pwats of 1.5+ inches. Whether that
risk is realized will depend upon if activity can train along the
approaching pre-frontal trough and/or cold front.

Clouds and precipitation at times will probably hold high temps in
the upper 70s to the middle 80s both days with Sunday favored to be
on the warmer side of those numbers.

Tuesday...

The initial shortwave trough probably will have moved east of our
region by Tuesday. This should result in somewhat lower humidity and
seasonable temps. Some of the guidance indicates a weak wave or two
of low pressure may be riding along a frontal boundary to our south
on Tue. This may generate onshore flow and keep highs in the 70s for
Tue We may even have a few showers or a bit of drizzle for a
time...but should be considerably less rainfall than Sun and Mon.

Wednesday through Friday...

Another potent shortwave trough dropping southeast towards the Great
Lakes will continue the relatively active weather pattern. More
showers and a few t-storms will be possible by the mid to late next
week.

Lastly...it is way too soon to know what level of impacts, if any,
Hurricane Lee will have across the U.S. east coast.
Regardless...high surf and dangerous rip currents will likely impact
our beaches next week especially during the latter half of the week.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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

18Z TAF Update...

This afternoon...Moderate Confidence.

VFR/MVFR outside of scattered strong t-storms generally
northwest of a HFD-ORH-LWM line through 03Z. Winds will be from
the SSW around 10 knots outside of any convection.

Tonight...High Confidence.

Scattered strong convection across the interior dissipates this
evening. Otherwise...Widespread IFR/LIFR ceilings return
overnight. Light southwest winds prevail.

Saturday...High Confidence

IFR ceilings early gradually improve to VFR by late
morning/early afternoon. Light southwest winds. Scattered
SHRA/TSRA.

Saturday night...High confidence.

IFR ceilings once again. Light SSW winds.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Sunday through Wednesday/...

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

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

Monday: Mainly MVFR, with areas VFR possible. SHRA likely,
chance TSRA.

Monday Night: MVFR/IFR conditions possible. Chance SHRA, slight
chance TSRA.

Tuesday: MVFR/IFR conditions possible. Slight chance SHRA.

Tuesday Night: Mainly MVFR, with local VFR possible. Chance
SHRA.

Wednesday: Breezy. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

This afternoon through Saturday night...

A mid-level ridge to the east will continue to support quiet
conditions across the coastal waters through Saturday night.
Winds will be 5-10kts out of the SSW through Saturday,
decreasing Saturday night. Can't rule out a pop up shower or
thunderstorm over the coastal waters Saturday.

Outlook /Sunday through Wednesday/...

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

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

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

Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers, slight chance of
thunderstorms.

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

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT this evening for CTZ002>004.
MA...Heat Advisory until 8 PM EDT this evening for MAZ003>007-
     010>019-026.
RI...Heat Advisory until 8 PM EDT this evening for RIZ001-002-004-
     005.
MARINE...None.

&&

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

Preliminary Local Storm Report
National Weather Service Boston/Norton MA
410 PM EDT Fri Sep 8 2023

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

0230 PM     Tstm Wnd Dmg     Bolton                  42.43N 71.60W
09/08/2023                   Worcester          MA   Fire Dept/Rescue

            5-6 trees snapped in a stright line along
            Route 117/Main St.

&&

Preliminary Local Storm Report
National Weather Service Boston/Norton MA
418 PM EDT Fri Sep 8 2023

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

0253 PM     Tstm Wnd Dmg     1 E Lowell              42.64N 71.30W
09/08/2023                   Middlesex          MA   Public

            In Lowell wires were down on Rodgers St.

0300 PM     Tstm Wnd Dmg     1 WSW Lowell            42.63N 71.35W
09/08/2023                   Middlesex          MA   Trained Spotter

            In Lowell, there were wires down on
            Monadnock Ave.

&&

Special Weather Statement
National Weather Service Boston/Norton MA
428 PM EDT Fri Sep 8 2023

MAZ002-003-082130-
Western Franklin MA-Eastern Franklin MA-
428 PM EDT Fri Sep 8 2023

...A strong thunderstorm will impact portions of north central
Franklin County through 530 PM EDT...

At 427 PM EDT, Doppler radar was tracking a strong thunderstorm over
Colrain, or near Greenfield, moving northeast at 35 mph.

HAZARD...Winds in excess of 40 mph, pea size hail, and heavy rain in
         excess of 1-2 inches.

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...
Bernardston, Shelburne, Colrain, 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.

A Severe Thunderstorm Watch remains in effect until 1100 PM EDT for
western Massachusetts.

&&

LAT...LON 4273 7251 4260 7269 4266 7278 4273 7271
TIME...MOT...LOC 2027Z 218DEG 30KT 4267 7269

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

KP

Preliminary Local Storm Report
National Weather Service Boston/Norton MA
439 PM EDT Fri Sep 8 2023

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

0340 PM     Tstm Wnd Dmg     Bernardston             42.67N 72.55W
09/08/2023                   Franklin           MA   Law Enforcement

            Tree and power lines down on Brattleboro
            Road. Relayed by amateur radio.

&&

Preliminary Local Storm Report
National Weather Service Boston/Norton MA
441 PM EDT Fri Sep 8 2023

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

0240 PM     Tstm Wnd Dmg     Chelmsford              42.60N 71.37W
09/08/2023                   Middlesex          MA   Public

            Numerous trees down and snapped. Straight
            line SW to NE after the heavy rainfall.

&&

Special Weather Statement
National Weather Service Boston/Norton MA
450 PM EDT Fri Sep 8 2023

MAZ003-008-010-011-082145-
Western Hampshire MA-Eastern Hampden MA-Eastern Franklin MA-
Eastern Hampshire MA-
450 PM EDT Fri Sep 8 2023

...A strong thunderstorm will impact portions of central Hampshire,
central Franklin and north central Hampden Counties through 545 PM
EDT...

At 450 PM EDT, Doppler radar was tracking a strong thunderstorm over
Southampton, or near Holyoke, moving northeast at 25 mph.

HAZARD...Winds in excess of 40 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...
Holyoke, Amherst, Northampton, Deerfield, South Hadley, Easthampton,
Montague, Southampton, Hadley, Sunderland, Hatfield, Williamsburg,
Leverett, Shutesbury, Westhampton, Whately, Pelham, and New Salem.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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.

A Severe Thunderstorm Watch remains in effect until 1100 PM EDT for
western Massachusetts.

&&

LAT...LON 4219 7271 4224 7280 4257 7258 4244 7231
TIME...MOT...LOC 2050Z 214DEG 20KT 4226 7272

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH

KP