137
FXUS61 KBOX 261756
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
156 PM EDT Thu Sep 26 2024

.SYNOPSIS...
An approaching frontal system will bring showers with
moderate-heavy downpours and a few embedded thunderstorms today into
this evening. High pressure builds back in Friday through Monday and
will bring dry and very pleasant weather. The next chance of
rain showers comes toward the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Update: 10:45AM

Bit of a gloomy Thursday with an abundance of clouds and areas
of rain, which is concentrated across Connecticut, though spotty
showers are moving into central Massachusetts. Will continue to
see this trend into this afternoon before more widespread rain
and perhaps a few rumbles of thunder late afternoon into the
evening hours. Overall the forecast is on track, did update the
POPs to reflect the latest radar trends.

Previous forecast discussion:

A robust northern stream trough exits the Great Lakes
today, bringing several slugs of showers and possibly a rumble of
thunder.  With deep southwest flow aloft and southerly winds at the
surface, PWATS increase up to 1.8 inches.  Light to moderate rain
initially expands from west to east this morning.  Later in the
afternoon to evening, forcing increases 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, bringing a fine line of moderate to
heavy showers from NW to SE.  There could be a rumble or two of
thunder with the fine line, but not expecting severe weather with
only 100-300 J/kg of elevated instability and less than favorable
low and mid-level lapse rates less then 5C/km.  With warm cloud
depths around 11kft, the main threat along the fine line will be a
brief period of heavy rain.   The fine line will move quickly across
the region, limiting the flash flood threat.  The fine line moves
offshore around late Thursday evening, with drying conditions
overnight.   When its all said and done, the highest QPF totals look
north of the MA pike, with a 50 to 70% chance of one inch and a 10
to 20% chance for two inches per the HREF.  The chances for one inch
decrease to 20-40% south of the MA pike, but a widespread quarter to
half an inch looks likely.

Temperatures today warm into the upper 60s to low 70s with warm air
advection.  Dewpoints will also rise today into the mid to upper
60s.  Winds turn NW behind the cold front, but overnight temps stay
milder in the upper 50s to low 60s.

&&

.SHORT TERM /FRIDAY/...
Northern stream trough moves off to the NE Friday with rising
heights behind.  Guidance has trended Friday cloudier with mid-level
moisture streaming north from an upper level cut off over the SE
U.S.  With a little bit of mid-level convergence and some shortwave
energy, there could be some light sprinkles or drizzle south of the
MA pike.  Temperatures on Friday warm in the low to mid-70s but
could end up underachieving with more clouds than the sun.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Highlights...

* Dry & very pleasant weather through early next week

* Next chance of rain showers comes Tue or Wed.

Details...

A quiet and dry stretch of weather returns for the weekend into at
least the first first part of next week thanks to a building mid
level ridge and surface high pressure ridge centered over southern
Quebec. Subsidence should keep any precipitation chances at bay as
the high keeps remnants of Helene from moving into the northeast.
There`s no real change of airmass in the mid levels going into the
weekend but the placement of high pressure to our northeast and the
low to our southwest will direct cooler onshore surface air into
southern New England once again. This means the weekend is a bit
cooler than Friday, especially along the east coast where highs will
remain in the mid to upper 60s. Further inland low to mid 70s are
possible.

Next week high pressure remains in control on Monday but some
uncertainty is introduced by Tuesday with our next disturbance; a
trailing frontal system approaches from the west as well as
potential for a glancing blow from a coastal low to the south. Still
lots of timing and placement details to work out but rain chances
will increase later Tuesday into Wednesday. Ensembles indicate a 50-
60% chance of rain by Wednesday. Temperatures continue to be
seasonable with highs in the upper 60s/low 70s and lows in the 50s.

&&

.AVIATION /18Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:

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

Rest of Today...Moderate confidence.

MVFR/IFR CIGs as light to moderate rain, the potential for a
fine line of moderate to heavy rain with IFR/LIFR conditions
moves quickly west to east across region in the late afternoon
through the evening. While not likely, there may be embedded
thunder in the fine line. Winds remain out of the south this
afternoon, with gusts to 20 knots near the coast.

Tonight...Moderate confidence.

Low-end MVFR to IFR CIGs overnight, but rapid improvement from
northwest to southeast as the fine line exits the region,
sometime after 08z. There could be some patchy ground fog
overnight, but with winds turning NW, fog shouldn`t become
dense or widespread.

Tomorrow...High confidence.

VFR with light northerly winds. Localized sea breezes develop
near the coasts.

Tomorrow Night...High Confidence.

VFR, CIGs are 4,000 to 6,000 in southwest New England. Light
north winds.

BOS TAF...Moderate Confidence in TAF.

MVFR to IFR CIGs this afternoon and overnight along with -SHRA,
at this point do not feel strongly TSRA will occur. A fine line
of moderate to heavy rain does develop and move through 02z-07z
which will reduce visibilities and temporarily lower CIGS to
LIFR. Rapid improvement to VFR 10z to 12z. A sea-breeze is also
possible on Friday, around 18z.

BDL TAF...Moderate Confidence in TAF.

MVFR with light rain a fine line brings a period of moderate to
heavy rain and IFR/LIFR CIGS this afternoon. A rumble of thunder
is not out of the question this afternoon, though at this point
do not feel strongly TSRA will occur. Will AMD TAF if confidence
increases this afternoon/evening.

Outlook /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 Friday...High Confidence.

Small Craft Advisories remain in effect for the outer waters,
with wave heights still around 5-6 feet. With winds finally
turning southerly today through Friday, seas begin to diminish
below 5ft Friday.


Outlook /Friday Night through Monday/...

Friday Night through Saturday: Winds less than 25 kt.

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory until 8 PM EDT this evening for MAZ007-019-
     022-024.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT Friday for ANZ250-254-255.
     Small Craft Advisory until 2 AM EDT Friday for ANZ251.
     Small Craft Advisory until 8 PM EDT this evening for ANZ256.

&&

$$

SYNOPSIS...BW/KP
NEAR TERM...Dooley/KP
SHORT TERM...KP
LONG TERM...BW
AVIATION...BW/Dooley
MARINE...BW/KP