Flash Flood Warning 60, NWS Boston/Norton, MA

131 
WGUS71 KBOX 102055
FFSBOX

Flash Flood Statement
National Weather Service Boston/Norton MA
455 PM EDT Sun Sep 10 2023

MAC017-027-102105-
/O.CAN.KBOX.FF.W.0060.000000T0000Z-230910T2215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Middlesex MA-Worcester MA-
455 PM EDT Sun Sep 10 2023

...FLASH FLOOD WARNING IS CANCELLED FOR EAST CENTRAL WORCESTER AND 
NORTH CENTRAL MIDDLESEX COUNTIES...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

LAT...LON 4267 7148 4265 7139 4255 7133 4240 7147
      4253 7168

$$

Nash

Area Forecast Discussion
National Weather Service Boston/Norton MA
1055 AM EDT Sun Sep 10 2023

.SYNOPSIS...
Very warm and humid weather will persist today and tomorrow with
more showers and thunderstorms at times. Decreasing rain chances
Monday night, although cloudy and muggy weather continues into
Tuesday. A frontal system interacting with subtropical moisture
may bring soaking rains to parts of Southern New England
Wednesday. Our weather turns seasonable and much drier Thursday,
although Hurricane Lee still could make a close pass to Southern
New England later next week or next weekend. Increasing surf
and rip currents are likely to begin around Tuesday and continue
into the weekend, although there is low confidence in any other
impacts. Refer to the latest forecasts on Hurricane Lee from
the National Hurricane Center.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Showers already getting underway across portions of southern New
England this morning. Latest SPC mesoanalysis indicated
surface-based CAPE values in excess of 1500 J/kg already south
of the Mass Pike. Mixed layer CAPE values were mainly 500-1000
J/kg across southern New England. There was also a little more
shear evident, but it remained on the weaker side. Expecting
showers to blossom across our region late this morning into the
afternoon. Thunderstorms will be tougher to pin down. Not as
concerned for the risk of strong winds versus the potential for
downpours today. Some locations across our region have seen
significant rainfall since Friday, and are less able to handle
additional rainfall. Will be monitoring radar closely into this
evening. Those with outdoor plans today should keep an eye on
the sky, and move indoors if a thunderstorm approaches your
location.

Not expecting much sunshine today, so only minor tweaks to
temperatures. Did also try to tweak rainfall chances and timing.
Liked the latest runs of the RAP and HRRR in that regard.

710 AM Update:

Adjusted PoP/Wx following recent HRRR/CAM-based trends.

Lots of fog and stratus around this morning as a stalled
frontal boundary roughly extends from PSM southward thru HFD to
the lower Hudson Valley. Recent RAP model soundings show a
little more optimism for some breaks in cloud cover but
anticipate cloudier conditions than not for today.

Focus for later this morning and especially aftn turns to re-
development of thunderstorms. As mentioned with more clouds than
sun today that heating and therefore instability may be a little
less than prior days. However seems as though the majority
(non-NAM-based) CAMs blossom increasing coverage of showers and
t-storms roughly northwest of I-95 and primarily concentrated
within a few miles either side of a HFD-ORH-LWM line in vicinity
of the diffuse frontal boundary. METARs in the Delmarva
Peninsula and ongoing convection in the same area seems to
support evidence of a weak low pressure which seems likely to
ride along this stalled boundary. T-storm activity may begin as
soon as late morning but may become more probable into the 1-3
pm timeframe, then shifting east. High warm cloud depths and
tall-skinny profiles of instability support idea of heavy
downpours. Though its still uncertain who may see
thunderstorms, CAM- based signals show potential for
several/multiple rounds of storms in the aforementioned HFD-
ORH-LWM corridor. While severe weather potential is low, think
there is a risk for heavy rain and localized street flooding,
potentially of rapid-onset if occurring in an urbanized area.
Portions of the area are in a Slight Risk for excessive rain
from the Weather Prediction Center.

Previous discussion:

Subtropical ridge to the east and a stalled front to the west
continue result in a more or less unchanged air mass in southern New
England for today. Muggy conditions continue with dewpoints in the
low to mid 70s. Day will start with overcast low clouds and a patchy
fog. Unlike the previous few days, not expecting a whole lot of
lifting/mixing out of cloud cover during the late morning or early
afternoon. Instead, BKN to OVC skies should persist for most of the
day. Lack of sunshine will keep temperatures in the upper 70s to low
80s. Thermodynamic profile continues to support afternoon
instability. With a moderately strong jet aloft and a deamplifying
wave traversing over the region this afternoon and tonight, we will
experience another round of showers and thunderstorms today. Risk
for strong to severe storms is much lower than yesterday as both
lapse rates and shear will be lacking significantly. Nonetheless,
PWATs > 1.5 inches and a few hundred J/kg of instability should
support some heavy downpours and a few rumbles of thunder. Weak
boundary later winds will support slow moving heavy showers which
may cause some flooding issues that would likely be limited to
urban, poor drainage, and small stream flooding. 00Z HREF ensemble
mean is suggesting the potential for a swath of 2 to 3 inches of
rain across interior southern New England between this afternoon and
tomorrow morning. A few isolated showers may be possible this
morning, but expect showers and storms to become more numerous
generally after 1PM and continuing into tonight.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Tonight

Shower/thunderstorm activity begins to wane after midnight as low-
pressure associated with a deamplifying short-wave aloft exits south
and east of southern New England. Temperatures will drop a bit more
than previous nights with lows forecast to be generally in the mid
60s. This should be more comfortable than the upper 60s/low 70s that
have been observed for the last few nights. More patchy fog
development prior to day break.

Tomorrow

More unsettled weather on Monday as a subtle short-wave at 500 hPa
progresses over the region. Temps in the upper 70s/low 80s and
dewpoints in the low 70s will continue to support modest diurnal
instability with 1000 J/kg of CAPE likely across the region. Shear
will be a bit stronger and lapse rates will be steeper tomorrow,
thus any storms that develop may be more of a threat compared to
what's expected today. Having said that, the overall synoptic
forcing is on the weaker side, so we would generally expect generic
thunderstorms with some modestly gusty winds, heavy downpours, and
thunder and lightning. One or two strong storms may be possible, but
otherwise just expect some thunder and heavy downpours.

&&

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

* Trending drier Mon night, though potential for fog and stratus
  lingering into part of Tue.

* Wet weather returns with showers/t-storms bringing potential for
  soaking rain somewhere in Southern New England Wed.

* Seasonable and dry late week, although monitoring developments
  regarding Hurricane Lee in this period into the weekend.

* Increasing rip current risk and high surf Tue into part of next
  weekend on beaches with southern and southeast exposures.

Details:

Monday Night into Tuesday:

For Monday night the weak area of low pressure partly responsible
for daytime showers/embedded t-storms moves NE during the late
evening and overnight hrs. Showed decreasing PoP for the evening and
overnight and should eventually go under 15% PoP for overnight. One
thing the forecast doesn't currently reflect (due to uncertainty)
but may need to be introduced is areas of fog. In addition, there
are a majority of model solutions which show a ridge of high
pressure nosing down coastal ME/NH and bringing a period of onshore
flow. Adds up to generally overcast and still fairly muggy
conditions.

For Tues, onshore flow and related OVC then looks to continue for
part of the day, then gradually starts to disperse into the later-
morning to early afternoon. While there may be widely scattered
showers in the intervening hrs after stratus dissipates, limited
insolation in spite of continued humid/muggy weather should
translate to equally limited instability, thus only supporting a
risk for showers vs thunder. All this occurs in a background
synoptic setting of large-scale height falls as a stronger mid/upper
level disturbance moves into the Gt Lakes. Highs mid 70s to lower
80s, although will still be rather muggy (dewpoints mid/upper
60s).

Tuesday Night through Wednesday Night:

Active weather resumes in this period, especially later-overnight
and into Wed. The mid/upper-level trough over the Gt Lakes gradually
swings ENE into the Northeast states Tue night into Wed, spreading a
pretty strong cold front into New England into Wed. Ahead of this
will be a continued influx of subtropical moisture favoring
potential for efficient downpours (warm cloud depths >10 kft, PWAT
values 1.6-1.8 inches, tall-skinny vertical profiles of instability)
in showers and t-storms. Anticipate rains becoming more likely
during the second half of the evening into Wed, where PoP was raised
into the high likely to low categorical range (70-80%). QPF
probabilities across the various model ensemble systems show fairly
solid 40-60% probs for 1 inch or more of QPF in a 24 hr period
ending 12z Thurs. Thus growing confidence on soaking rains for Wed
somewhere in SNE, but there's still too much variance in solutions
as far as which area(s) may be more favored with some keying on
interior MA/CT while others focusing on the I-95 corridor. In
addition, some solutions show a weak area of low pressure along the
front as it moves ENE and that could serve a focus for heavier
rains. These details will need refining over the coming days but it
is looking like Wed especially is favoring a washout. Showed
decreasing rain chances for Wed night into early Thursday, along
with a substantial decrease in dewpoints/humidity levels into the
50s! Highs range around the mid 70s with lows Wed night into the
mid 50s to low 60s.

Will also mention the increasing risk for rip currents on south-
facing beaches as related to Hurricane Lee in the open
Atlantic, as 4- 6 ft long-period swell sets in around Tue night
and Wed. It seems likely that at least a rip current statement
would be needed for these south-facing exposures at some point
by mid next week, which then is likely to continue into at least
early in the weekend as seas build further.

Thursday into the Weekend:

High pressure brings about a cooler, drier air mass into Southern
New England at least into Thurs, if not longer. Increasing northerly
breezes in response to a 1024+ mb high pressure over the Gt Lakes
ridging in should take place Thurs and perhaps lingering into Fri
too. Highs in the 60s to lower 70s, pretty seasonable for mid
September climo standards.

However will be closely monitoring developments regarding Hurricane
Lee, which may still make at least a close pass to the Northeast at
some point in this period. However there is still large uncertainty
as far as where and when Lee makes its northward turn and for how
long that northward trek may take place. That will be dictated by
several steering forces, among them including the strength of
ridging over the north Atlantic/Atlantic Canada. Thus confidence
remains low in any direct impacts Southern New England may see
related to Lee, which still may make a close pass to the Northeast.
However we can still probably expect strong riptides and high surf,
carrying over from the Tue/Wed timeframe, for our beaches. For the
latest information on Hurricane Lee, see the latest forecast,
advisories and Key Messages from the National Hurricane Center.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

Today: Moderate Confidence

IFR/LIFR cigs lift to MVFR by late morning/early afternoon,
except ACK which should stay at IFR through the day. Modest
south winds with scattered showers and possibly a few
thunderstorms developing late this morning but especially
afternoon (as soon as 16z, more likely around/after 18z).
Thunderstorms may be more concentrated in the BED-ORH-BDL
corridor, but may include BOS as well; less likelier potential
for PVD and the South Coast, Cape airports.

Tonight...High Confidence

IFR/MVFR ceilings overnight with VCSH. Winds becoming southeast,
but remaining light.

Tomorrow...Moderate Confidence

IFR/MVFR ceilings early should lift to VFR by late morning early
afternoon. Still expecting extensive cloud cover, but cloud
bases forecast to be between 040-060. Light east/southeast
winds.

KBOS TAF...Moderate confidence in TAF. IFR may scatter to MVFR
by 16z. Increasing risk for TS as soon as 16z, but more likely
after 19z.

KBDL TAF...Moderate confidence in TAF. IFR/LIFR to improve to
MVFR by 16z; increasing risk for TS as soon as 16z but more
likely after 18z.

Outlook /Monday Night through Thursday/...

Monday Night through Tuesday: Mainly VFR, with local IFR
possible. Slight chance SHRA.

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

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

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

Thursday: VFR. Breezy. 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 Night through Thursday/...

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

Tuesday: Winds less than 25 kt.

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

Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft. Rain showers likely, slight chance of thunderstorms.

Wednesday Night: Winds less than 25 kt. Local rough seas. Rain
showers likely, slight chance of thunderstorms.

Thursday: Winds less than 25 kt. Local rough seas. Chance of
rain showers.

&&

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

&&

SYNOPSIS...Loconto/RM
NEAR TERM...Belk/Loconto/RM
SHORT TERM...RM
LONG TERM...Loconto
AVIATION...Belk/Loconto/RM
MARINE...Loconto/RM

Special Weather Statement
National Weather Service Boston/Norton MA
142 PM EDT Sun Sep 10 2023

CTZ002>004-MAZ004-009>012-101830-
Hartford CT-Tolland CT-Windham CT-Southern Worcester MA-
Western Hampden MA-Eastern Hampden MA-Northern Worcester MA-
Eastern Hampshire MA-
142 PM EDT Sun Sep 10 2023

...Thunderstorms With Heavy Rain and Minor Flooding Across Portions
of Northern Connecticut and Central Massachusetts...

At 141 PM EDT, Doppler radar was tracking several strong
thunderstorms along a line extending from near Union to Hartford.
Movement was north at 10 mph.

HAZARD...Heavy Rainfall and Minor flooding.

SOURCE...Radar indicated.

IMPACT...Minor nuisance flooding of typically flood prone areas.

Locations impacted include...
Worcester, Springfield, Hartford, New Britain, West Hartford,
Manchester, Chicopee, East Hartford, Enfield, Westfield, Holyoke,
Glastonbury, Newington, Vernon, Windsor, Agawam, West Springfield,
Wethersfield, Mansfield, and South Windsor.

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.

&&

LAT...LON 4221 7288 4226 7183 4164 7187 4163 7196
      4166 7216 4171 7224 4169 7227 4167 7227
      4164 7233 4160 7234 4159 7247 4164 7250
      4163 7271 4161 7271 4158 7276 4158 7281
TIME...MOT...LOC 1741Z 195DEG 9KT 4196 7218 4175 7269

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...<30 MPH

Nash

Special Weather Statement
National Weather Service Boston/Norton MA
210 PM EDT Sun Sep 10 2023

MAZ013-016-018-019-101900-
Eastern Plymouth MA-Western Norfolk MA-Eastern Norfolk MA-
Western Plymouth MA-
210 PM EDT Sun Sep 10 2023

...Thunderstorms Producing Heavy Rain and Minor Flooding Will Impact
Portions Of Norfolk and Plymouth Counties...

At 207 PM EDT, Doppler radar was tracking several thunderstorms from
near Weymouth to around Cohasset. These storms were moving northeast
at 15 to 20 mph.

HAZARD...Heavy Rainfall and Minor flooding.

SOURCE...Radar indicated.

IMPACT...Minor nuisance flooding of typically flood prone areas.

Locations impacted include...
Brockton, Weymouth, Braintree, Randolph, Marshfield, Hingham,
Scituate, Pembroke, Rockland, Abington, Duxbury, Whitman, Hanover,
East Bridgewater, Holbrook, Norwell, Hull, Hanson, Cohasset, and West
Bridgewater.

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.

&&

LAT...LON 4201 7100 4218 7106 4233 7085 4229 7076
      4222 7069 4207 7059
TIME...MOT...LOC 1807Z 227DEG 19KT 4216 7087

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...<30 MPH

Nash

Preliminary Local Storm Report...Summary
National Weather Service Boston/Norton MA
233 PM EDT Sun Sep 10 2023

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

0120 PM     Flood            Cranston                41.77N 71.48W
09/10/2023                   Providence         RI   Fire Dept/Rescue

            2 cars stuck in street flooding on Scituate
            Avenue and Phenix Avenue flooded and
            impassable. relayed by Amateur Radio.

0140 PM     Flood            Cranston                41.77N 71.48W
09/10/2023                   Providence         RI   Law Enforcement

            Oaklawn Avenue flooded and impassable.
            Relayed by Amateur Radio.

0140 PM     Flood            Providence              41.82N 71.42W
09/10/2023                   Providence         RI   Law Enforcement

            Magnolia Street flooded and impassable.
            relayed by Amateur Radio.

0145 PM     Flood            1 SW Providence         41.81N 71.44W
09/10/2023                   Providence         RI   Public

            social media post showing water covering
            lanes of Rt 10 at Union Ave.

0203 PM     Rain             1 SSE North Providence  41.84N 71.45W
09/10/2023  M1.13 inch       Providence         RI   Public

0215 PM     Flash Flood      Providence              41.82N 71.42W
09/10/2023                   Providence         RI   Emergency Mngr

            multiple water rescues due to vehicles
            stalled in water. Route 10 closed. Several
            manhole covers pushed up.

0201 PM     Flood            2 NW Millbury           42.22N 71.79W
09/10/2023                   Worcester          MA   Public

            Washout and minor flooding in Worcester
            under roughly 4-6 inches of water in two
            locations on Millbury Street at Winnipeg and
            Cliff Streets. Reported by Trained Spotter.

0142 PM     Flood            Cohasset                42.23N 70.80W
09/10/2023                   Plymouth           MA   Law Enforcement

            Portion of Chief Justice Cushing Road
            flooded and impassable. Relayed by Amateur
            Radio.

0126 PM     Rain             1 E Framingham          42.30N 71.41W
09/10/2023  M1.37 inch       Middlesex          MA   Public

0140 PM     Flood            Wayland                 42.37N 71.37W
09/10/2023                   Middlesex          MA   Law Enforcement

            Bridge Road and Anthony Road flooded and
            impassable. relayed by Amateur Radio.

&&

Special Weather Statement
National Weather Service Boston/Norton MA
234 PM EDT Sun Sep 10 2023

MAZ004-005-026-101930-
Northwest Middlesex County MA-Central Middlesex County MA-
Northern Worcester MA-
234 PM EDT Sun Sep 10 2023

...Showers and thunderstorms with heavy rain will impact portions of
east central Worcester and north central Middlesex Counties through
330 PM EDT...

At 232 PM EDT, Doppler radar was tracking showers and thunderstorms
moving northeast across the region.

HAZARD...Minor flooding.

SOURCE...Radar indicated.

IMPACT...Minor nuisance flooding of typically flood prone areas.

Locations impacted include...
Lowell, Leominster, Chelmsford, Dracut, Westford, Acton, Pepperell,
Tyngsborough, Groton, Lunenburg, Littleton, Lancaster, Ayer, Shirley,
Stow, Harvard, Boxborough, Bolton, and Dunstable.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4271 7125 4270 7125 4242 7150 4251 7173
      4270 7152 4270 7129 4272 7127
TIME...MOT...LOC 1832Z 215DEG 34KT 4255 7153

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...<30 MPH

KC

Special Weather Statement
National Weather Service Boston/Norton MA
255 PM EDT Sun Sep 10 2023

MAZ018-019-101945-
Eastern Plymouth MA-Western Plymouth MA-
255 PM EDT Sun Sep 10 2023

...A strong thunderstorm will impact portions of northern Plymouth
County through 345 PM EDT...

At 254 PM EDT, Doppler radar was tracking a strong thunderstorm over
Hanson, or 7 miles northeast of Bridgewater, moving northeast at 25
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...
Brockton, Bridgewater, Marshfield, Hingham, Scituate, Pembroke,
Rockland, Abington, Duxbury, Whitman, Hanover, East Bridgewater,
Kingston, Norwell, Hull, Hanson, Cohasset, Halifax, West Bridgewater,
and Plympton.

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 4193 7081 4203 7101 4231 7081 4226 7071
      4210 7062
TIME...MOT...LOC 1854Z 213DEG 23KT 4204 7086

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

KP

Special Weather Statement
National Weather Service Boston/Norton MA
311 PM EDT Sun Sep 10 2023

MAZ022-102000-
Barnstable MA-
311 PM EDT Sun Sep 10 2023

...Slow Moving Thunderstorm Producing Heavy Rain and Minor Flooding
Across the Upper Cape...

At 309 PM EDT, Doppler radar was tracking a thunderstorm near
Sandwich that has moved very little and is producing heavy rainfall.

HAZARD...Minor flooding.

SOURCE...Radar indicated.

IMPACT...Minor nuisance flooding of typically flood prone areas.

Locations impacted include...
Sandwich, Bourne, and Mashpee.

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.

&&

LAT...LON 4164 7054 4176 7059 4183 7050 4176 7034
TIME...MOT...LOC 1909Z 239DEG 5KT 4179 7048

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...<30 MPH

Nash