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351
FXUS61 KBOX 061925
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
325 PM EDT Thu Jun 6 2024

.SYNOPSIS...
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A second round of scattered showers and thunderstorms should
cross the region late this afternoon and evening. Unsettled
conditions continue with scattered showers and thunderstorms
Friday through Monday, but it will not be a washout on any of
those days.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Just started to see some breaks in the clouds across western MA.
Visible satellite data showed some convective looking clouds
under development as well. Still not seeing big warning signs
for widespread severe weather. MUCAPE values should be 500-1,500
J/kg, with MLCAPE values less than 500 J/kg. Effective shear
had increased to about 30-35 kt this afternoon. Lapse rates
remained marginally supportive for thunderstorms at all.
Thinking is that our region will be dealing with weakening
thunderstorms from farther west as they move into a less
favorable environment, just before sunset or later. Will monitor
any thunderstorms through this evening. The primary risk would
be locally heavy rainfall, and perhaps some gusty winds.

A weak surface low pressure should move off the coast towards
midnight. Not much of a pressure gradient to speak of, so
expecting rather light winds. Currently forecasting the majority
of showers and thunderstorms to dissipate by shortly after
midnight. Humidity may lower some late tonight, but it will
still fell muggy for most. Stratus and patchy fog should
gradually lift overnight from west to east.
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&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
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Tricky forecast for Friday. it looks like our region will get on
the back side of a cool front to start the day, only to have
another weak low pressure potentially approach late in the day.
While humidity will be considerably less than what we had in
place today, it should still be enough to support a few showers.
Thinking the risk for thunderstorms has diminished across
southern New England. More sunshine will mean higher max
temperatures region-wide.

Humidity should continue to drop slightly Friday night. Mainly
clear skies and light SW to W winds should keep the stratus and
fog at bay. Above normal temperatures continue.
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&&

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

* Unsettled Friday through Sunday with several chances for rain
  and isolated Thunderstorms

* Pattern improvement delayed until early/mid next week as low
  pressure over southern Canada is displaced by building mid-
  level ridge

Friday...

Broad upper level low that has been slowly creeping towards New
England from the northwest sets up shop over the Great
Lakes/southern Canada by early Friday. Several shortwaves will
rotate around the low, the first of which develops mid day
Friday while somewhat of a seabreeze/back door coastal front
drops south out of Maine. While the dynamics of the day don`t
look super impressive, thinking that some scattered showers and
thunderstorms will be able to develop in the convergence zone of
the two "forcing features" where some modest instability,
~600J/kg SBCAPE is present. 0-6km bulk shear also looks to be
supportive of thunderstorm development, topping out around 60kt
Friday afternoon! At present, this convergence zone appears to
set up between Worcester and Boston along I-495, but may shift
over the next 24 hours.

The limiting factors in storm coverage and strength are typical
of southern New England with lackluster mid level lapse rates,
less than 5C/km, and decreasing PWATs as surface cold front
approaches from the west; PWATs drop from near 1.8" early Friday
to 1". So, while the severe potential remains very low, cant
rule out some solid downpours and gusty winds Friday afternoon.

Overall, should see a mix of sun and showers with a moderate
mugginess to the air with dewpoints in the low and mid 60s the
first half of the day.

Saturday and Sunday...

Unsettled conditions continue Saturday and Sunday, though
neither day appears to be a washout with a few more shortwaves
rotating around the persistent upper level low.

Saturday looks to be the drier of the two days as PWATs fall to
around 0.8" behind surface cold front that passes through
overnight. Guidance is split on the shower potential, with more
coarse resolution global guidance, like the GFS, trending
towards a drier day and hi-res guidance like the NAM initiating
more widespread shower activity Saturday afternoon. Dynamics
appear to be more supportive of thunderstorms, compared to
Friday, as mid level lapse rates increase to ~6C/km and low
level lapse rates approach 8.5C/km, but instability appears to
be quite poor, around 200J/kg.

PWATs surge back towards 1.25-1.4" early Sunday with a similar
dynamic setup, which will yield more showers and isolated
Thunderstorms compared to Saturday. Still, not expecting a
washout, with a mix of sun and showers.

Early next week and beyond...

Very persistent mid level trough/low pressure over Canada,
remains near stationary through early next week. Guidance shows
stronger shortwave development in the Monday period that could
bring a more substantial shot of QPF to the region, before a
brief reprieve from unsettled conditions develops
Tuesday/Wednesday with some indication that strong mid level
ridging develops during that timeframe. While ridging looks
robust, temperatures look seasonably mild rather than hot, with
highs in the 80s.
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&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
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Forecast Confidence Levels:

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

Through 00Z...Moderate confidence.

Mix of mainly MVFR/IFR across the region, with some VFR briefly
developing across the western half of southern New England.
A second round of scattered showers and t-storms with locally
heavy rainfall will impact interior MA into CT late this
afternoon. SE-S wind 5-15 kt.

Tonight...Moderate confidence.

Scattered showers and t-storms will weaken as they move into
the coastal plain this evening, then drying out overnight. IFR-
LIFR conditions this evening may improve to VFR from W to E
06-12z, but stratus and patchy fog persisting across eastern MA.
Light to calm wind.

Friday...Moderate confidence.

Any lingering stratus will dissipate in the morning, otherwise
VFR. Scattered showers developing in the afternoon, mainly north
of the Mass Pike. SW wind 5-15 kt, with sea-breezes developing
along the coast.

Friday Night...Moderate confidence.

Mainly VFR. SW to W winds 5-15 kt.

KBOS TAF...Moderate confidence.

KBDL TAF...Moderate confidence.

Outlook /Saturday through Tuesday/...

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

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

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

Monday: VFR. Slight chance SHRA.

Monday Night: VFR.

Tuesday: VFR. Slight chance SHRA.
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&&

.MARINE...
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Forecaster Confidence Levels:

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

Moderate confidence through Friday Night.

Main concern across the coastal waters will be reduced
visibility in fog tonight, visibility improves Friday into
Friday Night. Marginal 5-foot seas continue, so maintained the
Small Craft Advisory.

Outlook /Saturday through Tuesday/...

Saturday through 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.
Chance of rain showers, isolated thunderstorms.

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

Monday through Monday Night: Winds less than 25 kt.

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

.BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT Friday for ANZ254.
     Small Craft Advisory until 7 AM EDT Saturday for ANZ255-256.
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&&

$$

SYNOPSIS...Belk/KS
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...KS
AVIATION...Belk/KS
MARINE...Belk/KS