043
FXUS61 KBOX 071436
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1036 AM EDT Fri Jun 7 2024

.SYNOPSIS...
Warmer today with decreasing humidity levels but scattered
afternoon and evening showers developing as an upper level
disturbance approaches. Cooler tonight, then mainly dry and
seasonable conditions Saturday. Unsettled conditions return
Sunday through midweek with a few showers at times but it will
not be a washout.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Forecast remained largely on track this morning, but did make
some adjustments to account for observed trends. Fog had
largely dissipated as of this writing, but the stratus clouds
will take a little longer to break up. In fact, these could
linger much of the day across the Cape and islands.

Latest SPC mesoanalysis showed a lot of shear across southern
New England, but not much buoyancy. MLCAPE values of < 100 J/kg
and MUCAPE values of 500-700 J/kg does not raise alarms for
strong thunderstorms later today. Likely to only be dealing with
isolated to scattered showers this afternoon. The majority of
these showers should be closer to the cold pool aloft over
northern New England and the Great Lakes.

Previous Discussion...

Stratus and fog along eastern MA coast will lift this morning
leading to plenty of sunshine, but sct-bkn diurnal cu will
develop this afternoon as steep low level lapse rates develop
with shallow moisture at the top of the boundary layer. Upper
low sets up north of the Gt Lakes with shortwave energy rotating
around the low which will likely result in scattered afternoon
showers developing, especially north of the MA Pike closest to
the cold pool aloft. While there is marginal instability with
SBCAPES up to 500 J/kg, soundings show a pronounced mid level
cap which will limit updrafts so not expecting any t-storms,
just some low topped showers. Better chance of thunder will be
to the north under the cold pool aloft. Fairly warm low level
temps today with 850 mb temps reaching 12-14C which will support
highs in the low-mid 80s, but 70s along the immediate coast as
sea-breezes develop. Humidity levels will be dropping in the
interior, especially this afternoon as dewpoints fall through
the 50s.

&&

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

The upper low and cold pool will be moving into northern New
England tonight with decent mid level cooling southward into
SNE. This will help to continue the shower threat into this
evening, then clearing overnight as cold front moves off the
coast with drying W flow. Lows will settle into the 50s.

Saturday...

The upper low will be lifting to the north with warming 500 mb
temps. Expect plenty of sunshine mixing with some clouds as
diurnal cu develops. Shower threat will be less than today, with
just a low risk for a spot shower across northern MA. Otherwise
a dry day but becoming breezy with W winds gusting to 20-30 mph
in the afternoon as we will have a well mixed boundary layer in
post frontal airmass. Cooler and dry airmass with highs mid-
upper 70s, but closer to 70 higher terrain. Dewpoints dropping
to the upper 40s and lower 50s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Highlights

* Scattered showers on Sunday

* Drier to start the week with a few spot showers possible on
  Monday

* Lower than normal confidence for days 5 through 7 which could
  range from a long stretch of unsettled weather to a brief
  unsettled period on Tuesday followed by warmer and drier
  weather to finish out the week

Sunday

A robust short-wave disturbance aloft will traverse across the
Northeast on Sunday. With sufficient moisture in place to the
tune of 1 to 1.25 inch PWATs, we`re likely to see scattered
showers across the region on Sunday afternoon. Even areas that
miss out on rain are likely to experience overcast skies
throughout the day with cooler temps peaking in the low 70s.

Monday

A cold front associated with the aforementioned upper-level
disturbance pushes through the region Sunday night into Monday.
This should support a drier day for most of southern New
England, but with the quasi-stationary upper-level low still
overhead there could be some unsettled weather as well. Latest
suite of model guidance keeps the core of the cold pool aloft
over northern New England where there will be higher precip
chances. Can`t rule out the possibility for some spot showers at
this time, but those details will be resolved as we edge closer
to next week.

Tuesday through Thursday

Forecast confidence drops off substantially early next week as
there is considerable spread in how the latest suite of forecast
models are handling a short-wave embedded in the broader
cyclonic flow over the eastern US. Several solutions favor this
short- wave cutting off as it digs over The Great Lakes and into
the Midwest. From there feature meanders near the northeast for
several days which would support unsettled weather for much of
next week. Other solutions keep the short- wave embedded in the
larger flow which would support an unsettled day Tuesday
followed by a mid-level ridge building over the eastern US to
end the week. In this scenario we would see a warming/drying
trend mid to late next week. Given the low confidence in the
forecast , have leaned on the NBM for guidance for days 5
through 7 which places slight chance to chance PoPs across much
of the region daily with seasonable temperatures.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

IFR/LIFR across eastern MA, Cape Cod and the Islands continues
to lift into this afternoon. It`s more questionable near ACK,
where IFR may linger most of today. We continue to show some
improvement to VFR after 18z as we`re hopeful that fog/stratus
will burn off there as well, but it`s possible these lower
conditions prevail all day. Even if there is brief improvement,
LIFR is expected to return toward sunset across the Cape and
Islands.

Otherwise, VFR today through Sat. There may be some widely
scattered showers this afternoon, especially across western and
northern MA, but coverage should be limited.

Light W/SW winds today through Sat. Coastal sea breezes develop
later this morning.

KBOS TAF...High confidence.

KBDL TAF...High confidence.

Outlook /Saturday Night through Tuesday/...

Saturday Night: VFR. Breezy. Slight chance SHRA.

Sunday: VFR. Breezy. Chance SHRA.

Sunday Night through Monday: VFR. Slight chance SHRA.

Monday Night: VFR.

Tuesday: VFR. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

High confidence through Saturday.

S-SW winds developing this afternoon with locally onshore winds
near the coast as sea-breezes develop. Winds become W tonight
behind a cold front, then increasing W wind Sat with gusts to
20 kt, with potential for some 25 kt gusts over eastern MA
nearshore waters. Lingering 5 ft seas over southern waters
through tonight where SCA will continue. Areas of fog will
reduce vsbys over the southern waters into this evening,
improving overnight as winds shift to W.

Outlook /Saturday Night through Tuesday/...

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

Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers.

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

Monday through Monday Night: Winds less than 25 kt.

Tuesday: Winds less than 25 kt. Slight chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ254>256.

&&

$$

SYNOPSIS...KJC/RM
NEAR TERM...Belk/KJC
SHORT TERM...KJC
LONG TERM...RM
AVIATION...KJC/RM/JWD
MARINE...KJC/RM