319
FXUS61 KBOX 171120
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
720 AM EDT Wed Jul 17 2024

.SYNOPSIS...
Dangerous heat and humidity will continue today. Scattered
showers and thunderstorms will move into the region this evening
before weakening. A cold front will bring much more comfortable
temperatures and dewpoints to the region starting Thursday
afternoon with dry conditions expected through the weekend.

&&

.NEAR TERM /THROUGH THURSDAY/...
Key Points

* Dangerous heat and humidity continue today with heat indicies of
  95-100F

* Another round of strong to severe thunderstorms between 4pm - 10pm.

One more day of dangerous heat and humidity with high temps in the
low 90s and dewpoints in the low 70s. This will bring heat indices
up to 95F to 100F again this afternoon. The high heat and humidity
will once again prime the atmosphere for another round of strong to
severe thunderstorms. A potent shortwave drops out of the Great
Lakes late today with a surface cold front out ahead of it. Moderate
amount of instability will be available ahead of the cold front with
HREF mean SBCAPE values around 1200 J/kg, and HREF max around
2000J/kg. Modest 0-6km shear of 25-30 knots will be sufficient
enough for organized convection. Once again, mid level lapse rates
are not favorable only around 5C/km. With strong forcing from the
cold front and unidirectional shear, the primary storm mode will
likely be a linear cluster of storms moving from west to east. The
primary severe threat will be strong to damaging wind gusts with low
level lapse raters around 10C/km and DCAPE values between 600-800
J/kg. Heavy rain is the only secondary threat with PWATS around 2.0
inches and warm cloud depths around 11kft. Not anticipating any
flash flooding with the fast moving nature of thunderstorms. Hail
and tornadoes do not appear to be a threat today due to weak mid
level lapse rates and meager low level shear.

Hi-res guidance from the HREF is in pretty good agreement of timing
and strength of storms this afternoon/evening. The best chance for
seeing strong to severe winds gusts is across western MA and CT,
where better instability will be available. Storms will weaken as
they move east into eastern MA and RI as they begin losing the
support of daytime heating and run into more stable marine air.
Storms look to enter western MA and CT around 4-6pm and weaken and
move offshore between 8-10pm

&&

.SHORT TERM /THURSDAY NIGHT/...
Key Point

* Still warm and muggy overnight

Showers and possibly a rumble or two of thunder could linger near
the coastal waters through about 2am, otherwise drying conditions
overnight. Even with the passage of the cold front, the cooler temps
and lower dewpoints lag far behind the front not arriving until
Thursday afternoon. Overnight temperatures stay in the upper 60s to
low 70s with dewpoints remaining near 70F. Low status and fog will
fill in for the southcoast, Cape, and Islands one last time before
drier air will kick it out Thursday afternoon.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Key Point

* Dry and seasonal weather Thursday through this weekend

After an extended period of hot, muggy, and unsettled weather, a
major pattern change is store for SNE starting Thursday. Drier air
and cooler temps arrive Thursday afternoon with PWATS falling below
1.0 inches and dewpoints falling into the low 60s to even upper 50s,
and staying there through the weekend. Temperatures will be much
more comfortable Thursday and Friday with highs in the low to mid
80s, warming into the upper 80s for the weekend. Overnight lows will
also stay more comfortable in the low to mid 60s, even some upper
50s, through the weekend.

As for precipitation, high pressure and rather dry airmass will drop
down from Canada helping suppress rain and thunderstorm chances
through the weekend. Next chance for precip looks to be Tuesday or
Wednesday next week as a shortwave drops into the southern plains
before lifting north into the Northeast.

&&

.AVIATION /11Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:

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

Today...Moderate to high confidence.

VRF inland. For the Cape and Islands, VFR dropping back to IFR
in the evening. Moderate to high confidence that thunderstorms
will move into western MA and CT around 22-00z, and move east
through 02-04z. As storms approach the east coast, they will
likely fizzle into light rain showers. SW winds at 10-15 knots
gusting 20-25 knots.

Tonight...Moderate confidence

Showers could linger through midnight. VFR for western terminals
overnight. VFR/high end MVFR for northern terminals. low end
MVFR/IFR for southern terminals including the Cape and Islands.
SW winds turning west at 5-10 knots, gusting 20-25 knots near
the waters.

Tomorrow and tomorrow night...High confidence.

Gradual clearing becoming VFR for all terminals in the
afternoon. West winds at 10 to 15 knots.

KBOS TAF...Moderate confidence in TAF.

VFR today with SW winds at 10-15 knots. Line of thunderstorms
should weaken into light rain showers as they approach the
terminals between 01-04z.

KBDL TAF...High confidence in TAF.

VFR with SW winds at 10-15 knots. Line of thunderstorms likely
reaching the terminal sometime between 23z-02z.

Outlook /Friday through Sunday/...

VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through tomorrow: Moderate confidence.

Gusty SSW winds continue today into tonight up to 25 knots. Seas
climb to 4-6 feet tonight into Thursday. Winds turn west
Thursday as the surface cold front moves through. The cold front
will also help to kick out the low status and fog that has been
stuck over the southern waters for the past few days.
Thunderstorms will weaken as they approach the waters tomorrow
evening, but could still bring brief gusty winds above 30 knots
with occasional lightning.


Tides and Rip Currents.

A rip current statement is in effect today due to the moderate
to high risk for rip currents. Strong southerly winds of
20-30mph and waves between 4-6 feet will likely cause strong rip
currents to occur for south facing beaches. Another rip current
statement will likely be needed tomorrow with waves increasing
to 5-7 feet.


Outlook /Friday through Sunday/...

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

Friday Night through Sunday: Winds less than 25 kt.

&&

.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>021-026.
     High Risk for Rip Currents through this evening for MAZ020>024.
RI...Heat Advisory until 8 PM EDT this evening for RIZ001>007.
     High Risk for Rip Currents through this evening for RIZ006>008.
MARINE...Small Craft Advisory until 8 AM EDT Thursday for ANZ232.
     Small Craft Advisory from 2 PM this afternoon to 8 PM EDT
     Thursday for ANZ235-237.
     Small Craft Advisory until 8 PM EDT Thursday for ANZ254>256.

&&

$$

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