581
FXUS61 KBOX 081819
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
Issued by National Weather Service New York NY
219 PM EDT Wed May 8 2024

.SYNOPSIS...
Another round of scattered showers and thunderstorms will move
across the region this afternoon and this evening. Periods of
unsettled weather continue late this week into this weekend with
showers at times. Temperatures will average below normal late this
week into the weekend. Milder/Seasonable temperatures should return
early next week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Key Points...

* Another round of scattered showers and t-storms possible this
  afternoon and evening. A few strong to marginally severe storms
  possible, with hail the primary threat

A mid-level shortwave moves into New England this afternoon and
evening. This is expected to set off some additional showers and
thunderstorms this evening. Good cooling aloft as 500 mb temps drop
to -16 to -18C will result in rather steep mid level lapse rates 7-
7.5 C/km overspreading the region. This will contribute to MUCAPES
500-1000+ J/kg developing across much of the region late this
afternoon. We have already seen some convective storms start to fire
well northwest of the region. While storms may be mostly elevated,
potential exists for marginally severe hail given impressive
effective bulk shear values of 50+ kt along with steep mid level
lapse rates. SPC has all of SNE within a marginal risk but it
appears focus for strongest storms will be from northern CT through
interior MA.

There is some uncertainty regarding the extent of surface based
instability this afternoon due to presence of cooler low level
airmass. Damaging wind threat will be dependent on surface based
storms developing. Best chance of SBCAPES up to 1000 J/kg will be
across western MA and northern CT as these areas may sneak into the
warm sector ahead of a cold front, and decent low level lapse rates
develop here. This is where strong to damaging wind threat will be
highest with any strong storms.

Any convection that does develop should come to an end prior to
midnight, with drier air working into the region behind the storms.
Expect some clearing conditions especially across the interior.
There is a chance that some stratus and patchy fog may linger in the
coastal plain. Lows will be in the upper 40s and lower 50s.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Thursday starts out dry as a wedge of dry air remains in place over
SNE. Moisture increases from the SW during the afternoon ahead of
next shortwave dropping through the Great Lakes and OH valley, with
low pressure moving to mid Atlantic region. Risk of showers will
increase during the afternoon. Highs should be mostly in the 60s,
mildest CT valley and coolest along the coast in eastern MA where
developing NE flow will likely hold temps in the upper 50s here.

These showers will continue into Thursday night. With cloud cover
and rain, temperatures across much of the area will remin in the
middle and upper 40s.

&&

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

* More widespread rain possible Friday into Saturday night

* Below average temperatures continue through the weekend

* More seasonable temps return next week

Friday

A shortwave trough exits out of the Ohio River Valley becoming
negatively tilted as it moves over SNE. The surface low is initially
vertically stacked with the shortwave aloft and begins to occlude as
new low forms and intensifies offshore to the east. Although the
best forcing will be to the south of SNE, the chances for a
widespread rain are increasing. As a mid level low passes over and
intensifies to the south of the region, this will drag down rather
cold 850mb air around 0C to -2C. With ENE winds at the surface,
along with cold 850mb temps, low clouds, and rain, high temps may
struggle to even reach 50F across the region. Rain looks to continue
into Friday night before tapering off Saturday morning. Overnight
lows look to drop into the low 40s, with upper 30s possible in the
high terrain. Not out of the question that snow mixes in with rain
across the high terrain in the Berkshires.

Saturday

Surface and midlevel low move well out to sea bringing widespread
rain to end in the morning. However, an upper level closed low drops
south over the region leaving SNE under cyclonic flow aloft.  With
weak forcing aloft and the mid level cold pool still in place, this
will likely lead to a hit or miss light showers/drizzle. High temps
on Saturday don`t look to recover much with thick low level cloud
layer still around. High temps should only reach the low to mid 50s
with continued onshore flow.

Sunday

Another weak surface low exits the Ohio River Valley and passes just
south of SNE.  This could bring another round of widespread light
rain to the region. Uncertainty with this system remains high given
the weak upper level forcing and not much run to run consistency on
the track of the low. Highs remain below normal Sunday and could
once again struggle to reach 50F.

Next week

The pesky upper level low and mid level cold pool finally move east
as a midlevel shortwave brings WAA and 850mb temps above 0C to even
+10C by mid week.  This will allow high temps to moderate back into
the low to mid 70s. As for rain chances, high pressure to the south
should keep things dry early in the week. Rain chances look to
increase again mid to late week, but uncertainty is high at this
time.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Forecast Confidence Levels:

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

18z TAF Update...

Stubborn RA/SHRA will continue over KBOS/KBED/KFMH and KHYA for
the next hour or so before pushing offshore. Latest satellite
showing broad clearing across western terminals so expect some
brief improvement in cigs into early afternoon before any
convective activity pushes into the area from eastern NYS.
Elsewhere for the eastern terminals, IFR conditions look to
continue into the afternoon.

Today...Moderate confidence.

A round of scattered showers/t-storms remains possible 19-00z,
with best chance from northern CT northward through interior MA.
Have maintained VCTS for all terminals given the low confidence
in coverage. Some hail is possible with the afternoon/early
evening activity. A period of SW gusts to 20 kt and pockets of
LLWS possible this afternoon across SE MA and Cape/Islands as
LLJ develops and moves across the region.

Tonight...Low to moderate confidence.

SHRA/TS exits into the waters early this evening. Some clearing
is possible tonight for western MA/CT but stratus and patchy
fog may linger across eastern MA and RI. Extent of IFR
conditions is uncertain. Light winds.

Thursday...Moderate confidence.

A period of VFR/MVFR conditions after 12Z trending to
widespread MVFR in the afternoon as more showers develop. N wind
5-15 kt becoming NE.

KBOS TAF...Moderate confidence in TAF. Scattered showers and
possible t-storms redevelop to the north and west this afternoon
and may move across BOS mid-late afternoon. IFR cigs look to
remain at least through 09Z Thursday, possibly lasting into the
morning push.

KBDL TAF...Moderate confidence in TAF. Another round of
scattered showers or t-storm possible this afternoon and we have
maintained the VCTS in the TAF given the uncertainty in coverage.
IFR cigs look to remain at least through 09Z Thursday, possibly
lasting into the morning push.

Outlook /Friday through Monday/...

Thursday Night: MVFR/IFR conditions possible. Breezy. Chance
SHRA.

Friday through Friday Night: MVFR/IFR conditions possible.
Chance RA.

Saturday: MVFR/IFR conditions possible.

Saturday Night: Mainly VFR, with areas MVFR possible. Slight
chance SHRA.

Sunday: Mainly VFR, with local MVFR possible. Chance RA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Thursday...High confidence.

Low level jet will bring a period of SW gusts to 20+ kt to south
coastal waters this afternoon and evening. Winds diminish
tonight, becoming north by Thu morning then NE 10-20 kt during
Thu afternoon. Seas remain below SCA thresholds. Areas of fog
will reduce vsbys at times over south coastal waters through
tonight. Scattered showers and embedded t-storms move through
this morning into early afternoon.

Outlook /Friday through Monday/...

Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Chance of rain showers.

Friday through Friday Night: Winds less than 25 kt. Seas up to
5 ft. Slight chance of rain.

Saturday: Winds less than 25 kt. Seas up to 5 ft.

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

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

&&

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

&&

$$