281
FXUS61 KBOX 251857
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
257 PM EDT Wed Sep 25 2024

.SYNOPSIS...

An approaching frontal system will bring showers with moderate
heavy downpours and few embedded thunderstorms mainly Thursday
into Thursday evening. High pressure builds back in Friday
through Monday and will bring dry and very pleasant weather.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

930 AM Update...

* Considerable clouds today with highs in the middle-upper 60s

Surface high pressure over the Canadian Maritimes coupled with a
lingering upper level ridging will result in mainly dry weather
today. Weak warm advection aloft and onshore flow may result in
a brief sprinkle/spot shower or two especially across northern
MA. Overall...expect mainly dry weather today but the onshore
flow will result in considerable cloudiness. The risk for a few
showers may increase across the distant interior by early
evening...as a bit better forcing approaches from the west.
Plenty of clouds and onshore flow will result in highs mainly in
the middle to upper 60s.

&&

.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 WEDNESDAY/...

Key Points...

* Dry & very pleasant weather Fri into early next week
* Next threat for some showers not until later Tue and/or Wed

Details...

Tranquil and generally dry weather is expected Friday into early
next week...although a few showers may linger into early Friday
morning towards the Cape/Islands but that would be short-lived.
This in response to closed low shifting east of the Canadian
Maritimes and a mid level ridge axis building to our northwest.
There will be a surface high pressure system moving across
Quebec coupled with a distant offshore low pressure system. So
we will need to watch for periods of clouds as we have seen of
late with the onshore flow.

Overall...expect pleasant cool nights and mild days from Friday into
early next week. Overnight low temps should bottom out mainly in the
upper 40s to the middle 50s with the coolest readings in the typical
low-lying locations. High temperatures will mainly be in the lower
to middle 70s except 65 to 70 degrees near the immediate coast and
parts of the high terrain.

Mid level ridge axis will keep our weather dry into early next week.
How quickly this mid level ridge axis shifts east of the
region...but there will be some shortwave energy approaching from
the west. This may bring us a period of showers...but not until
later Tue and/or Wed.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...

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 line of convective showers that crosses
the region from west to east in the late afternoon. CIGS clear
quickly to MVFR/VFR behind the line of showers.

BOS TAF...Moderate Confidence in TAF.

Today & Tonight:
Mainly VFR with pockets of MVFR possible with ESE winds 8-12
kts. CIGs lower overnight into MVFR. VCSH early Thursday morning.

Thursday:
MVFR with a few showers. SE winds becoming SSE in the afternoon.
Slightly lower confidence in timing of the main batch of
showers/embedded thunder. Likely will push across in the
afternoon-early evening timeframe. Periods of lower CIGs into
IFR possible.

BDL TAF...Moderate Confidence in TAF.

Today & Tonight:
VFR/MVFR again today with ESE winds. Showers and IFR CIGs move
in overnight.

Thursday:
MVFR. SHRA in the morning. With increasing chances for rain and
embedded thunder by the afternoon. Brief IFR possible in heavier
showers.

Outlook /Friday through Monday/...

Friday: Mainly VFR, with local MVFR possible.

Friday Night through Monday: 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 Monday/...

Friday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers.

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

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

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents until 8 PM EDT this evening for MAZ007-
     019-022-024.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT Friday for ANZ250-254.
     Small Craft Advisory until 11 PM EDT Thursday for ANZ251.
     Small Craft Advisory until 8 PM EDT Thursday for ANZ255-256.

&&

$$

SYNOPSIS...KP/Frank
NEAR TERM...Frank
SHORT TERM...KP
LONG TERM...Frank
AVIATION...Mensch/Frank
MARINE...KP/Frank