BOX issues Area Forecast Discussion (AFD) at Sep 26, 3:15 AM EDT880
FXUS61 KBOX 260715
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
315 AM 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/...
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 /07Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Thursday...Moderate confidence
VFR/MVFR CIGS to start today, but become low end MVFR/IFR as
light to moderate rain spreads west to east this morning. A fine
line of moderate to heavy rain and IFR/LIFR conditions moves
quickly west to east across region in the late afternoon through
the evening. There could be some embedded thunder in this fine
line, so included prob30s for the interior terminals for TSRA,
even though lightning wont be frequent.
Thursday Night...Moderate Confidence
The fine line should clear the Cape and Islands around 06z, then
rapid clearing to VFR conditions is likely. There could be some
patchy ground fog overnight, but with winds turning NW, Fog
shouldn't become dense or widespread.
Friday... High Confidence
VFR with light northerly winds. Localized sea breezes develop
near the coasts.
BOS TAF...Moderate Confidence in TAF.
CIGS drop down to MVFR later this morning as light rain moves
in. A fine line will bring a brief period of moderate to heavy
rain and IFR/LIFR CIGS late in the afternoon to early evening.
There could be a rumble or two of thunder with the passage of
the fine line so opted to keep the prob30 for TSRA despite
confidence in frequent lightning is low.
BDL TAF...Moderate Confidence in TAF.
MVFR today with light rain moving in early this morning. A fine
line will bring a period of moderate to heavy rain and IFR/LIFR
CIGS this afternoon. There may be a rumble to two of thunder in
the afternoon.
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...None.
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...KP
SHORT TERM...KP
LONG TERM...BW
AVIATION...BW/KP
MARINE...BW/KP
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 26, 3:15 AM EDT----------------
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