818
FXUS61 KBOX 301935
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
335 PM EDT Sun Jun 30 2024

.SYNOPSIS...
A strong cold front will move off the coast tonight and push
the showers and thunderstorms offshore. An upper level
disturbance will bring hit or miss showers Monday and possibly
an isolated thunderstorm, otherwise dry weather with below
normal temperatures. High pressure brings dry weather,
seasonably warm temperatures and low levels of humidity for
Tuesday and Wednesday. Turning more humid and unsettled for the
Fourth of July thru the early part of the weekend with a couple
of disturbances offering chances for clouds, showers and
thunderstorms.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Weakening QLCS moving E from RI and expect a continued weakening
trend as storms push into south coastal MA due to stabilizing
effect of marine layer near the coast. Just showers north of
this line across central and eastern/NE MA. Scattered convection
developing further north along the cold front across eastern NY
and this activity has shown some increase in intensity.
Instability here is recovering with MLCAPES 1000-1500 J/kg so
expecting a second round of storms late afternoon and evening as
front approaches. Effective shear values quite impressive up to
55 kt so environment is very favorable for further
intensification with potential for severe weather as storms move
across MA.

Convection this evening will become focused south of the MA Pike and
gradually move offshore through midnight although could linger a bit
longer over the Cape/Islands. Otherwise, drying conditions behind
the cold front overnight as winds shift to NW bringing a dewpoint
drop into the 50s interior and low 60s near the south coast. Lows
will range from the upper 50s western MA and low-mid 60s eastern
MA.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Monday...

Sharp mid level trough with cold pool will be moving across the
region with 500 mb temps dropping to -16 to -18C. This cold pool
combined with daytime heating will result in BKN CU developing along
with widely scattered showers, mainly east of the CT valley and
especially across eastern MA. Marginal instability develops with
CAPES up to 500 J/kg so can`t rule out an isolated t-storm with
small hail given cold temps aloft. Temps will be a bit below normal
in post-frontal airmass with highs in the 70s and dewpoints in the
50s, to lower 60s near the coast.

Monday night...

Mid level trough moves offshore with rising heights as high pres
builds in from the west. Any diurnal clouds will melt away in the
evening leading to a mostly clear and somewhat cool night with light
north winds. Lows will range through the 50s, except lower 60s outer
Cape/Islands and Boston metro.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Highlights:

* Dry and warm with tolerable humidity levels for Tue and Wed.

* Turning more humid and active for Independence Day, and
  potentially into Fri/Sat too, with clouds, showers and storms
  possible. Exact timing remains uncertain.

30/00Z guidance suite was in rather good agreement with the overall
synoptic pattern. Broad mid level ridging to start out this portion
of the forecast is expected to transition to broad troughing towards
next weekend. At the surface, a large high pressure should be over
southern New England Tuesday into Wednesday. This high pressure
should be far enough offshore to permit a cold front to approach
from the west on Independence Day, but it is a little complicated.
The offshore high pressure may not permit this front to make it all
the way into, or through, our region before being driven back north.

Dry weather with near to slightly above normal temperatures Tuesday
and Wednesday. Increasing risk for some showers and isolated
thunderstorms Wednesday night into Thursday. Also expecting
increased humidity with above normal temperatures Thursday into
Saturday. The timing and coverage of these showers and thunderstorms
remains the most uncertain aspect of this forecast. With many
outdoor plans for the holiday, it would be best to monitor the
forecast over the coming days.

This uncertainty lingers late this week. As such, stayed close the
NationalBlend solution for now, as it is ensemble-based. This meant
a broad chance for showers and thunderstorms Friday into Saturday,
but am not expecting it to be raining this entire time.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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

Through 00z...

Cluster of storms moving through CT and RI through 20z before
weakening somewhat as they move further E. Additional
showers/storms likely will develop further in the interior
through early evening. IFR-LIFR cigs/vsbys Cape/Islands with
MVFR RI/SE MA with VFR elsewhere. Brief strong wind gusts and
lower conditions in any storms.

Tonight...Moderate confidence.

Showers and t-storms especially south of the MA Pike will end
from N to S through midnight. VFR interior with partial clearing
overnight. IFR-LIFR south coast and Cape/Islands improving to
VFR after midnight but lower cigs lingering at ACK. Wind shift
to NW 00-06z from W to E.

Monday...High confidence.

VFR cigs 4-6k ft developing with scattered showers developing
late morning through the afternoon, especially eastern MA. Can`t
rule out an isolated t-storm with small hail. N wind gusts to
20 kt.

Monday night...High confidence.

VFR with diminishing wind.

KBOS TAF...Moderate confidence in TAF.

Expect a few t-storms developing 20-00z with brief lower
conditions and potential for strong wind gusts. Included a
TEMPO group to highlight this potential. Otherwise VFR. SW
winds shift to W this evening then NW overnight.

KBDL TAF...Moderate confidence in TAF.

One cluster of t-storms moving to the E but expect additional
showers and storms into early evening. VFR but brief lower
conditions and strong wind gusts in any storms. Wind shift to
NW around 00z.

Outlook /Tuesday through Friday/...

Tuesday through Tuesday Night: VFR.

Wednesday: VFR. Breezy.

Wednesday Night: VFR. Breezy. Slight chance SHRA.

Independence Day: Mainly VFR, with local MVFR possible. Breezy.
Slight chance SHRA.

Thursday Night: VFR. Breezy. Slight chance SHRA.

Friday: Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight through Monday night...High confidence.

Gusty S-SW winds to 25 kt will be diminishing this evening as
modest low level jet moves offshore. Winds shift to NW overnight
then N during Monday with gusts to 20 kt. Diminishing N winds
Mon night. Showers and t-storms through this evening, moving
offshore from the south coastal waters late tonight.

Outlook /Tuesday through Friday/...

Tuesday through Wednesday: Winds less than 25 kt.

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

Independence Day through Thursday Night: Winds less than 25 kt.
Seas locally approaching 5 ft. Slight chance of rain showers.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ231-
     250.
     Small Craft Advisory until 11 PM EDT this evening for
     ANZ232>235-237.
     Small Craft Advisory until 6 AM EDT Monday for ANZ254>256.

&&

$$

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