❰ Current Conditions

Flood Watch

FLOOD WATCH REMAINS IN EFFECT FROM LATE TONIGHT THROUGH SATURDAY EVENING

Flood Watch issued July 12 at 2:54PM EDT until July 13 at 8:00PM EDT by NWS Boston/Norton MA

* WHAT...Flooding caused by excessive rainfall continues to be possible.

* WHERE...Portions of northern Connecticut, including the following areas, Hartford CT, Tolland CT and Windham CT, Massachusetts, including the following areas, Central Middlesex MA, Eastern Essex MA, Eastern Franklin MA, Eastern Hampden MA, Eastern Hampshire MA, Eastern Norfolk MA, Eastern Plymouth MA, Northern Bristol MA, Northern Middlesex MA, Northern Worcester MA, Southeast Middlesex MA, Southern Bristol MA, Southern Plymouth MA, Southern Worcester MA, Suffolk MA, Western Essex MA, Western Franklin MA, Western Hampden MA, Western Hampshire MA, Western Norfolk MA and Western Plymouth MA, and Rhode Island, including the following areas, Bristol RI, Eastern Kent RI, Newport RI, Northwest Providence RI, Southeast Providence RI, Washington RI and Western Kent RI.

* WHEN...From late tonight through Saturday evening.

* IMPACTS...Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. Flooding may occur in poor drainage and urban areas.

* ADDITIONAL DETAILS... - http://www.weather.gov/safety/flood

* INSTRUCTIONS...You should monitor later forecasts and be alert for possible Flood Warnings. Those living in areas prone to flooding should be prepared to take action should flooding develop.

Expires: July 13 at 5:00 AM EDT
NWS Area Forecast Discussion
Area Forecast Discussion
National Weather Service Boston/Norton MA
353 PM EDT Fri Jul 12 2024

.SYNOPSIS...

Isolated showers and possibly a rumble of thunder this evening.
Heavy showers and thunderstorms likely early Saturday morning
ending Saturday afternoon. Hot and humid weather returns for
Sunday into the middle of next week. Afternoon Heat Indices in
the 95-100+ degree range are likely which will eventually
require Heat Headlines. While Sunday is dry, the risk for
scattered showers and thunderstorms will exist in the Monday
through Wednesday time frame...but plenty of dry weather
expected over this time period too. Appears the heat and
humidity finally will break by Thursday and Friday.

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

Tonight and Tomorrow

Weak shortwave trough approaching from the Great Lakes will send
shortwave energy and increased moisture content to the region
overnight into tomorrow morning. With PWATS climbing to 2.0 inches
and warm cloud depths approaching 13kft, there is a good chance that
any rain that falls will be very heavy with rain rates AOA
2in/hr which could cause poor drainage and urban flooding. With
MUCAPE values around 500 J/kg per the 12z HREF, there could be
embedded thunderstorms tomorrow morning as well. Rain will move
from SW to NE early tomorrow morning with the heaviest rainfall
expected between 6am to noon. Latest guidance has trended the
heaviest rainfall further south along the south coast and
Islands. There could still be localized areas that see up to 3-5
inches of rain as seen in the 12z HREF 24 hour LPMM. Opted to
leave the flood watch up for all of SNE until better run to run
consistency can be established, but may need to be trimmed back
the north end with future updates. WPC has also downgraded much
of the region from a slight risk to a marginal risk for
excessive rain which makes sense given the southward shift.

Temperatures tonight remain quite warm in the
low 70s. Trended temperatures Saturday afternoon cooler into
the low to mid 80s with the expectation that thick cloud cover
and rain will be around all morning, lingering into the
afternoon. Could see some clearing by Saturday evening
esspically across the western interior MA.

There could be a second round of isolated convection in the
late afternoon across the western interior. Not expecting
anything severe with SBCAPE values around 1000 J/kg, sfc-6km
shear around 30 knots, and bad mid level lapse rates around 5
C/km.

.SHORT TERM /SATURDAY NIGHT/...

Tomorrow night:

Drying out with clearing skies due to rising heights overnight.
This will allow temperatures to at least cool into the upper
60s outside urban areas. Dewpoints will remain in the upper 60s
overnight making it feel quite muggy still. With the high
dewpoints and good radiational cooling, there could be areas of
fog that form overnight.

.LONG TERM /SUNDAY THROUGH FRIDAY/...

Key Points...

* Hot & Humid through Wed with Heat Indices 95-100+

* A few rounds of scattered showers/t-storms possible during
  the first half of the week.

* A less humid airmass finally arrives by the latter half of the
  week.

Details...

While the broader western Atlantic ridge remains in place directing
anomalously hot and humid air into the region, a transient ridge in
the zonal flow Sunday will provide a break from the wet weather and
clouds leading to a warm but dry day. This zonal flow then continues
through Tuesday with the first in a series of disturbances around
late Monday into Tuesday. This will bring the chance for unsettled
weather including thunderstorms; while instability will be there,
bulk shear is limited as are lapse rates so severe storms, if any,
should be isolated. The more robust looking severe potential looks
to be around Wednesday when deeper shortwave approaches from the
Great Lakes with a good deal of instability which may align with
favorable shear values depending on timing. Something to watch at
the very least.

Temperature-wise Sunday we`ll see temps creeping back up into the
low 90s in the first of several days of steadily increasing
temperatures. At this point, given dewpoints "only" in the mid to
upper 60s and low 70s conditions are marginal for a Heat Advisory
that, if necessary, would likely be limited to more southern areas
where the dewpoints are higher. The more concerning period for
dangerous heat and humidity will be Monday and Tuesday, perhaps even
Wednesday as the airmass warms (850 mb temps rise to the 20-22C
range) and w/SW flow pushes dewpoints back into the mid to upper
70s. Thus, we`ll also see little relief overnight with low temps
limited to the low to mid 70s. Finally, though, some relief from the
humidity is on the horizon as guidance indicates a cold front around
Thursday that has the potential to drop dewpoints significantly for
the first time in over a week.

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

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Rest of Today...Moderate Confidence

VFR with periods MVFR/IFR as showers move north. SSW at 5-10
knots may gust up to 25 knots this afternoon.

Friday Night...Moderate Confidence

VFR in the evening, becoming MVFR/IFR overnight. Rain begins to
move in from the south around daybreak.

Saturday...Moderate Confidence

Moderate to heavy rain and thunderstorms moves south to north,
but the extent north remains uncertain. Best chance for
thunderstorms looks to be between 11z-15z tomorrow morning, but
could linger into the early afternoon. Another round of
thunderstorms is possible in the late afternoon mainly across
the western interior.

Starting the day IFR/LIFR esspically during periods of heavy
rain. As rain moves off shore to the SE, northern terminals
will become VFR, while terminals near the south coast with
remain MVFR/IFR for the afternoon.

Saturday night...High Confidence

VFR expect over the Cape and Islands, where pockets of MVFR/IFR
will still remain.

KBOS TAF...Moderate confidence in TAF.

VFR this afternoon with light showers likely. IFR/LIFR early
Saturday morning with periods of heavy rain and thunderstorms
possible. VFR Saturday afternoon.

KBDL TAF...Moderate confidence in TAF.

VFR with light showers and possibly a rumble of thunder this
afternoon. MVFR/IFR by Saturday morning with periods of
moderate to heavy rain and thunderstorms possible. VFR Saturday
afternoon

Outlook /Sunday through Wednesday/...

Sunday through Sunday Night: VFR.

Monday: VFR. Breezy. Slight chance SHRA, isolated TSRA.

Monday Night: VFR. Slight chance SHRA, isolated TSRA.

Tuesday through Tuesday Night: VFR. Breezy. Slight chance SHRA.

Wednesday: VFR. Breezy. Chance SHRA, isolated TSRA.

.MARINE...
Forecaster Confidence Levels:

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

Marine

Tonight through Saturday night

Gusty SSW winds up to 30 knots prompted the issuance of small
crafts for the near coastal waters from Cape Cod Bay to Block
Island through 09z. Small crafts in the open waters remain into
Saturday for seas of 4-5 feet. Winds remain gusty from the SSW
tomorrow at 20-25 knots, before finally decreasing to 5-10 knots
Saturday night.
Outlook /Sunday through Wednesday/...

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

Sunday Night through Monday: Winds less than 25 kt.

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

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. Areas of seas approaching
5 ft. Slight chance of rain showers, isolated thunderstorms.

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch from late tonight through Saturday evening for
     CTZ002>004.
MA...Flood Watch from late tonight through Saturday evening for
     MAZ002>021-026.
RI...Flood Watch from late tonight through Saturday evening for
     RIZ001>007.
MARINE...Small Craft Advisory until 5 AM EDT Saturday for ANZ231>237.
     Small Craft Advisory until 9 AM EDT Saturday for ANZ254-255.
     Small Craft Advisory until 9 PM EDT Saturday for ANZ256.

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