BOX issues Area Forecast Discussion (AFD) at Sep 6, 10:11 PM EDT
383
FXUS61 KBOX 070211
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1011 PM EDT Fri Sep 6 2024
.SYNOPSIS...
Low clouds re-develop tonight with areas of patchy fog possible
across central MA and the fog prone areas (valleys, low- lying
areas). A cold front moving through Southern New England late
Saturday afternoon into the evening will bring a period of rain
showers to most areas, although some embedded thunderstorms are
possible for the Cape and Islands.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
10 PM update...
SNE in between systems with ocean storm to the east and
approaching trough to the west. Ridging and subsidence across
SNE will provide dry conditions. Stratus expanding west across
SNE this evening and will overspread the CT valley overnight.
Patchy fog expected to develop, most prevalent across the
interior and higher terrain. Higher dewpoints and cloud cover
will result in a milder night with lows mid 50s to lower 60s.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Saturday and Saturday Night:
Southern New England is located in weak sfc ridge axis between a
distant coastal low moving into Atlantic Canada, and an
approaching cold front associated with a robust upper level low
over the Great Lakes region.
Stratus which is forecast to re-develop tonight is expected to
carry over into the morning hours of Sat. This shallow layer of
moisture should begin to scatter by late morning to noontime,
allowing for at least some sunny breaks and warming temps in
eastern New England, though more cloud cover in interior CT and
MA ahead of the approaching front should lead to less
opportunity for warming. Despite the variable amts of cloud
cover, most of the daytime hrs on Sat are generally dry with
highs in the 70s, higher east and on the cooler range of 70s
west.
Our weather then becomes a little more active with the
approaching cold front, its west to east passage forecast to
take place during the mid-afternoon to midnight period with
fairly high confidence. Strong 500 mb height falls and
diffluence aloft acting on the surface cold front should favor
a narrow line of moderate showers, moving eastward from eastern
NY later Sat afternoon into the evening. Although there is
plenty of wind aloft with a highly sheared environment, because
of the lack of stronger heating, convective instability looks
pretty limited in most areas. So for most areas, thinking just a
short-lived period of showers which could come down at a decent
clip but shouldn't cause any significant concerns. The one area
that could see greater, though still low (30% or less) chance
for embedded thunderstorms is in coastal southeast New England
and the Cape and Islands during the evening to midnight period.
Pooling dewpoints in the mid 60s offshore result in an axis of
most-unstable CAPEs around 100-500 J/kg, higher in the waters
south of ACK. Opted to include a mention of thunder for these
areas, but the main mitigating factor is that the shear could
ultimately be too strong to generate anything more than just
heavier showers. More rapid clearing then takes place from west
to east for the 2nd half of the night, with NW winds increasing
and dewpoints falling through the 50s. Lows in the mid
40s/around 50 interior sites, and low-mid 50s for RI and eastern
MA.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Key points:
* Drying out following cold front Saturday night
* Slightly warmer than seasonable high temperatures for most the
period with cool nights
Details:
Not much going on in this period following the rain Saturday
night. The cutoff low continues northeastward through Quebec.
Cyclonic flow should remain through Sunday before high pressure
moves in Monday as ridging continues to build in the Great Lakes
region. This high pressure looks to remain in place for our
area through the rest of the week. Dew points Sunday look to be
in the 40s and settle into the 50s for the rest of the week as
milder air sticks around.
With high pressure settling in, nights look to be clear and
quiet. Strong radiational cooling will favor cooler temperatures
overnight throughout the week, especially on Sunday with 40s
forecast across the interior into eastern MA. Lows look to
remain in the 50s throughout the period. Blended in some of the
NBM 10th percentile towards the end of the period to account for
this pattern. Daytime hours look to be slightly warmer than
seasonable throughout the week with the clearer skies
continuing.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight...Moderate confidence in timing and location of
IFR/LIFR. High confidence in at least MVFR stratus.
MVFR to LIFR stratus redeveloping from E to W. Light N wind for
the interior and NE winds becoming N 10-15 kt Cape/Islands.
Saturday...Moderate confidence.
MVFR-IFR improving toward VFR late morning into the early
afternoon. Showers and lower cigs moving into western MA/CT
later in the day. N wind becoming S 8-15 kt in the afternoon.
KBOS TAF...Moderate confidence.
Saturday...Moderate confidence.
Ceilings gradually improve after 12Z and toward VFR at/around
15Z. Confidence lower in exact timing of VFR and when BKN
ceilings become SCT in the afternoon.
KBDL TAF...Moderate confidence.
MVFR to IFR stratus returns again late tonight, roughly 02-06Z.
Outlook /Sunday through Wednesday/...
Sunday: VFR. Breezy.
Sunday Night: VFR.
Monday: VFR. Breezy.
Monday Night through Wednesday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Saturday Night...High confidence.
Low pressures system tracks to the north/northeast passing east of
the bench mark overnight and reaching Nova Scotia as a strong gale
by Saturday evening. Building seas prompt Small Craft Advisories
across much of the waters into Saturday and diminishing seas
late Saturday night through Sunday morning. Period of gusty
northeast winds are 20 to 25 knots on the outermost waters, less
near shore though tonight. There will be a lull in the winds
Saturday, but will increase overnight into Sunday morning,
should be less than 20 knots.
High Surf Advisory on Saturday for all of eastern Massachusetts with
the exception of Boston Harbor, there a Rip Current Statement
is in effect. Rip Current Statement remains in effect for
Saturday for the southern coastal beaches of Massachusetts and
Rhode Island. Making these hazards more dangerous, many beaches
are not staffed with life guards post Labor Day Weekend. Those
heading to area beaches this weekend should take note whether or
not a life guard is on duty.
Outlook /Sunday through Wednesday/...
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Sunday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Monday through Wednesday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents until 8 AM EDT Saturday for MAZ007-019.
High Surf Advisory from 8 AM to 8 PM EDT Saturday for MAZ007-
019.
High Risk for Rip Currents through Saturday evening for MAZ015-016-
020-021-023.
High Surf Advisory until 8 PM EDT Saturday for MAZ022-024.
RI...High Risk for Rip Currents through Saturday evening for RIZ006>008.
MARINE...Small Craft Advisory until 10 PM EDT this evening for ANZ232.
Small Craft Advisory until 2 AM EDT Saturday for ANZ235-237.
Small Craft Advisory until 9 AM EDT Sunday for ANZ250-254>256.
Small Craft Advisory from 2 AM to 8 PM EDT Saturday for ANZ251.
&&
$$
SYNOPSIS...Loconto/Hrencecin/Mensch
NEAR TERM...Belk/KJC/Mensch
SHORT TERM...Loconto
LONG TERM...Hrencecin
AVIATION...Belk/Hrencecin/Mensch
MARINE...Dooley/Hrencecin
Source: BOX issues Area Forecast Discussion (AFD) at Sep 6, 10:11 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202409070211-KBOX-FXUS61-AFDBOX)
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