299
FXUS61 KBOX 251135
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
735 AM EDT Wed Sep 25 2024

.SYNOPSIS...
Weak high pressure will remain across the region today. An
approaching frontal system will bring showers with moderate to heavy
downpours starting Wednesday night through Thursday afternoon. High
pressure builds back in Friday through Monday and will bring dry and
very pleasant early fall weather.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Weak high pressure remains stretched from northern New
England again today, bringing another day of similar weather to
yesterday.  ESE onshore flow and mostly cloudy to overcast skies
will cap temps in the mid to upper 60s.  There could be patchy
drizzle again today in Eastern MA and RI.  Looking further west,
shortwave energy begins to arrive ahead of a potent northern stream
trough.  There could be a couple of light showers in the late
afternoon in Western MA and CT, but rain will struggle to reach the
ground due to mid-level dry air.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
Better moisture and forcing arrive late Wednesday night
as a warm front with a 30-knot LLJ.  Light rain spread west to east
and will become moderate to heavy by Thursday morning as PWATS
increase to 1.5-1.75 inches.  Forcing continues to increase Thursday
as the base of the northern stream trough swings through New York
while a 125-knot jet streak moves over SNE.  A cold front then moves
through SNE late Thursday afternoon to early evening.  With low
amounts of MUCAPE, around 100-300 J/kg, hi-res guidance is in good
agreement, bringing a fine line through.  Not expecting severe
weather with this fine line with very marginal instability and less
than favorable low-level lapse rates around 2-3 C/km.  With warm
cloud depths around 11kft, the main threat along the fine line will
be a brief period of heavy rain.  Rainfall rates could exceed 0.5
inches/hr.  The fine line will move quickly across the region,
limiting the flash flood threat.  With the low amounts of
instability, a few rumbles of thunder are possible on Thursday
afternoon.  The fine line moves offshore around late Thursday
evening, with drying conditions overnight.   When its all said and
done, the highest QPF totals look to be in northwestern MA, with
HREF LPMM QPF showing up to 2 inches.  Further south and east,
values begin to drop off, but a widespread 0.5 to 1 inch remains
possible even into the Cape and Islands.

Temperatures overnight Wednesday drop into the low to mid-50s region-
wide, then rebound into upper 60s to low 70s for Thursday.  Winds
turn south and gust 10-20mph.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Friday - Monday Upper-level closed low moves offshore to the east
while another blocking ridge settles in for Friday through the
weekend.  High temperatures quickly rebound Friday into the low to
mid-70s with dry conditions and sunny skies.  Temperatures moderate
slightly Saturday - Monday but stay in the upper 60s to low 70s.
With good radiational cooling conditions, overnight lows will drop
into the upper 40s to low 50s.  Patchy radiation fog is possible
with the longer nights and dewpoints in the mid to upper 50s.

Tuesday and beyond There is quite a bit of uncertainty heading into
this part of the forecast, as models are generally too quick to
break down blocking ridges.  Global deterministic guidance is in
good agreement with another potent trough dropping out of the Great
Lakes sometime mid to late next week.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:

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

Today...Moderate confidence.

VFR/MVFR today with mid level clouds hanging around 3kft. Winds
remain out of the ESE today at 5-10 knots.

Tonight...Moderate Confidence

Rain and IFR/LIFR CIGS move from west to east overnight.
Showers overnight should remain light with the heavier rain
holding off until Thursday

Thursday...Moderate confidence

Moderate to heavy rain with IFR/LIFR Cigs. There could be
embedded thunder and a fine line of convection that crosses the
region from west to east in the late afternoon. CIGS clear
quickly to MVFR/VFR behind the fine line.

BOS TAF...Moderate Confidence in TAF.

Mainly VFR with FEW-SCT MVFR layer. ESE winds.

BDL TAF...Moderate Confidence in TAF.

VFR/MVFR again today with ESE winds. Rain and IFR CIGs move in
overnight.

Outlook /Friday through Sunday/...

VFR.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Thursday...High Confidence.

Small Craft Advisories remain in effect for all outer open water
zones along with the northern near coastal waters for seas of 5-7
feet.  Winds remain east today at 10-15 knots, then turn SSE
overnight into Thursday at 15-20 knots.

Rip Current Statement remains in effect for eastern shorelines as
large easterly swells continue to pose a high risk for rip
currents.

Outlook /Friday through Sunday/...

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

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

Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents through this evening for MAZ007-019-022-
     024.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT Thursday for ANZ250-251-
     254>256.

&&

$$

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