001
FXUS61 KBOX 070604
AFDBOX

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

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH TODAY/...
2 AM update...

Cancelled the dense fog advisory as vsbys have improved,
however stratus and fog will persist overnight across eastern
MA and Cape/Islands. Vsbys will improve toward daybreak as
winds shift to NW behind the weak front.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM SATURDAY/...
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.

&&

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

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:

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

Through 12z...

IFR-LIFR stratus and fog across eastern MA and Cape/Islands may
improve away from the immediate coast. VFR in the CT valley with
improving conditions at ORH/PVD.

Today...Moderate confidence.

Any lingering stratus and fog along the immediate coast in
eastern MA will dissipate by 14z, but IFR conditions may linger
a few hours later at Cape Cod terminals. Lower confidence on
clearing at ACK and stratus may linger through the afternoon.
Scattered showers developing in the afternoon, especially
north of the Mass Pike. SW wind 5-15 kt, with sea-breezes
developing along the coast.

Tonight...High confidence.

Patchy fog and stratus possible into the evening at ACK,
otherwise VFR. Light wind.

Saturday...High confidence.

VFR. Increasing NW wind with gusts to 25 kt developing in the
afternoon.

KBOS TAF...High confidence in trends, but low confidence in
exact timing.

Vsbys have improved and not expecting LIFR vsbys as winds have
shifted to N. IFR stratus likely persisting until 12z, then low
clouds scattering out by 14z. Sea-breeze developing by 15z.


KBDL TAF...High confidence. VFR.

Outlook /Saturday Night through Tuesday/...

Saturday through 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.

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 Night 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.

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...Dense Fog Advisory until 8 AM EDT this morning for MAZ007-015-
     016-019-022>024.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ254.
     Small Craft Advisory until 7 AM EDT Saturday for ANZ255-256.

&&

$$

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