913
FXUS61 KBOX 141922
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
322 PM EDT Fri Jun 14 2024

.SYNOPSIS...

Second round of strong to severe thunderstorms expected through
early tonight ahead of a dry and pleasant Father`s Day weekend.
Several days of excessive heat and humidity are likely starting
Tuesday and lasting through next Friday.


&&

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

First round of thunderstorms, of which strong to severe wind gusts
and small hail to the Boston metro area has move seaward, though we
are not yet out of the woods with a second round of potentially
severe thunderstorms building later this afternoon and evening. At
present, cells are beginning to develop across southern New
York and southwestern Connecticut and western MA with an
agitated cumulus field bubbling ahead of the advancing cold
front over the Albany metro area. MLCAPE values of >1000J/km are
currently associated with the area of storm development in
southern New York, which is subsequently where the strongest
updrafts are being observed at this time. CAMs have really
struggled to accurately depict convection today, underestimating
or misplacing the geographic coverage storms, thus, they
provide limited utility in diagnosing the exact timing and
coverage of storms this evening. With that said, most if not all
of the HREF members hint at the development of a strong line of
storms after ~20Z.

SPC Mesoanalysis continues to depict a recovering environment
behind the first line of convection where skies have begun to clear
across western MA. MUCape Values are forecast to rebound to
~2000J/kg across part with mid level lapse rates rebounding to
between 6-6.5C/km while low level lapse rates remain primed
around 8C/km. DCAPE, which surged to between 800-900 ahead of
this afternoon`s convective line with good mixing, also look to
increase this afternoon back to similar values, which will renew
the damaging wind threat with any additional convection. Some
small hail was also observed in mid day storms, but freezing
levels to 12,000ft and meager MLLRs really put the damper on
the severe hail potential, so we expect similar trends with any
strong storms through this evening.

The eastward extend of the severe potential with a secondary linear
convective line remains in question as it will again be a race
against time/sunset as instability wanes around 00-01Z. So,
ultimately, we expect another line of impactful convection to
traverse across southern New England between ~21Z and 02Z
tonight. Unfortunately clearing will take some time behind the
cold frontal passage late this evening as trailing shortwave
trough will provide enough forcing, combined with residual PWATs
around 1.25", to renew shower chances from approximately the
Worcester to Willimantic N-S line, east. Shortwave trough axis
will not move seaward of the region until between 12-15Z
Saturday, so shower activity may linger across the Cape and
Islands through sunrise tomorrow morning. The good news is that
with little instability overnight, the severe threat really
drops off as cold front moves offshore, with perhaps a few
lingering rumbles of thunder possible between 11pm and 2AM.

&&

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

Departing cold front/deep digging shortwave will allow very, at
least for June, dry air to filter into the region on NW/N flow
tomorrow. PWATs are expected to drop to around 0.4" by 18/21Z
Saturday, yielding a gorgeous, comfortable start to Father`s day
weekend. Little cloud cover is expected, with dewpoints dropping
into the low and mid 40s by early evening. 850mb temperatures
between 8-10C will support highs in the mid 70s to low 80s.

Radiational cooling will be in play Saturday night. With very dry
airmass in place and mainly clear skies overhead, as well as
slackening winds, it is quite possible that low temperatures drop
into the low to mid 40s across northwestern MA by daybreak on
Sunday. Urban heat islands, like Boston and Hartford, will remain
our most mild localities, with lows around 60F expected.
Temperatures across the coastal plain will fall back into the
50s. This is our last shot of cool air for quite some time as
mid level ridging starts to build in to end the weekend.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...

Key Point:

 * Several days of dangerous heat/humidity Tue-Fri

Big story for next week continues to be likelihood of dangerous heat
and humidity starting Tue and peaking Wed-Fri. Ensembles are in very
good agreement on building strong upper ridge over eastern U.S.
through most of next week which lends increasing confidence. In
fact, 500 mb heights nearing 600 dm is something rarely seen in the
Northeast and is a very strong signal for record heat. This aligns
with EPS and NAEFS Situational Awareness Tables which show several
parameters outside of model climatology relating to temperature,
signaling potential for a highly unusual event.

We`re also seeing fairly high chances of afternoon highs well into
90s Tue-Fri, if not near 100 in some spots. More importantly,
daytime heat indices may reach as high as 105 degrees and there will
be little relief at night with nighttime heat indices in 70s.

Upper ridge also favors dry weather for much of next week, but it`s
possible we see widely scattered showers/storms, especially in Thu-
Fri timeframe as cold front approaches from Great Lakes.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

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

18z TAF Update: Moderate confidence (60%)

Main uncertainty is with timing of TS. First line moving
through eastern MA at 17z will move offshore by 19-20z, then we
are watching for a second line of TS to cross area between
20-24z ahead of cold front. Expect brief MVFR/IFR in any TS.

Otherwise VFR ceilings should prevail through tonight as SW
winds veer to W-NW and N overnight, except ceilings to lower to
IFR around Cape Cod and Islands. Slow improvement Sat morning
with VFR-MVFR ceilings gradually scattering out Sat afternoon as
N winds increase to 10-20kt with gusts to 25kt near coast.

KBOS TAF...Moderate confidence in TAF (60%). Best call on TS
timing is now through 19z, then another possible round 22z-00z.

KBDL TAF...Moderate confidence in TAF (60%). Best call on TS
timing is 21-23z.

Outlook /Sunday through Wednesday/...

Sunday through Sunday Night: VFR.

Monday: VFR. Breezy.

Monday Night through Juneteenth: VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight:

Steady light to moderate rain with embedded thunder possible.
Winds shift WNW and decrease to 5-10 knots overnight. Seas 2-3
feet.

Tomorrow:

Rain tapers off in the morning with clearing conditions in the
afternoon. Winds turn north and gust 15 to 20mph. Seas 2-4 feet.

Tomorrow Night:

Clear conditions and generally light winds. Seas around 2-4
feet.

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. Slight chance of rain
showers.

Tuesday through Juneteenth: Winds less than 25 kt.

&&

.CLIMATE...
Daily Record High Temperatures...

Tuesday, June 18th

BOS - 94F (1929)
BDL - 95F (1994)
PVD - 94F (1929)
ORH - 93F (1929)

Wednesday, June 19th

BOS - 96F (1923)
BDL - 95F (1995)
PVD - 94F (1923)
ORH - 93F (1923)

Thursday, June 20th

BOS - 98F (1953)
BDL - 97F (2012)
PVD - 95F (1941)
ORH - 93F (1953)

Last Day of 100F (or greater)

BOS - 100F (07/24/2022)
BDL - 100F (07/21/2019)
PVD - 100F (07/28/2020)
ORH - 102F (07/04/1911)

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for
     ANZ230>237-251.
     Small Craft Advisory until 11 PM EDT this evening for ANZ250-
     254.

&&

$$

SYNOPSIS...KS/JWD
NEAR TERM...KS
SHORT TERM...KS
LONG TERM...JWD
AVIATION...JWD
MARINE...KS/JWD
CLIMATE...Dooley