Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 281923
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
323 PM EDT Thu Mar 28 2024

.SYNOPSIS...
Low pressure moves up toward Nova Scotia tonight as cold front
moves off the coast. High pressure briefly builds in on Friday.
A weak clipper system passes through late on Saturday with
drying expected on Sunday. An area of low pressure will develop
over the Central Plains on Monday with a warm front extending
east into the Mid- Atlantic. This will lead to unsettled
conditions through at least the middle portion of next week
before drying out on Thursday.

&&

.NEAR TERM /THROUGH FRIDAY/...
Cold front continues to slowly work its way through the region, and
should be offshore after midnight tonight and through the pre-dawn
hours. Meanwhile surface low pressure off the Mid-Atlantic coast
will track out to sea tonight and move towards the Canadian Maritimes
Friday afternoon. Surface high pressure builds in from the west late
tonight through Friday as an H5 trough passes through the East Coast
during the day Friday.

Rain continues, mostly along the coast, into this evening, then
tapers off from west to east, and should be off the East Coast
around midnight tonight. Skies clear out tonight, and then skies
will be mostly sunny on Friday, though some mid and high clouds are
possible with the passage of the trough.

A tight pressure gradient forms between low pressure to the east and
high pressure building in from the west. Northwest winds will
increase to 10 to 15 mph tonight, and then will increase further to
15 to 20 mph with 30 to 35 mph gusts for most of Friday. Although
northwest flow will be in place behind a departing cold front on
Friday, there will be enough sunshine on Friday for high
temperatures to rise into the mid and upper 50s.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
High pressure will be located off the Southeast US on Friday night
as the area lies in between low pressure systems. Winds will
noticeably diminish overnight as most areas will settle underneath
the surface inversion. However, breezy conditions will continue at
higher elevations in excess of 30 mph. Lows will be in the 30s
areawide with clear skies.

Overall, the start of the weekend will be quite seasonable with
widespread sunshine for Saturday morning. Temps will rebound nicely
through the day with highs ranging in the mid to upper 50s to low
60s under modest southwest flow; which will aid afternoon mixing.
However, the sunny weather will be short-lived as clouds increase
through the afternoon as a weak clipper system transverses across
the area early Saturday night. This system will be weakening as it
approaches so not expecting a washout by any means. Isolated to
scattered rain showers are expected late Saturday into early
Saturday night before moving away from the area. The best chance for
shower activity is north of the Philadelphia area. Rainfall amounts
are minimal, generally less than a tenth of an inch.

After the clipper system passes by, weak high pressure will build in
from the Great Lakes and across the Northeast. This should result in
quiet weather on Sunday under partly cloudy skies. All in all, a
nicer day is expected with highs in the 60s despite a gusty
northwesterly breeze.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The long term period will be quite different from the short term as
an active, wet, and unsettled period looms. A stalled frontal
boundary will be located over the Carolinas as a low pressure system
develops over the Central Plains. This system will extend a warm
front eastward into the Mid-Atlantic region beginning as early as
Monday. The warm front will continue to nose eastward with time as
the low translates east toward the Great Lakes region by Wednesday.

This will lead to several opportunities for rain to be directed
toward our region. The first comes Sunday night into Monday where
PoPs are around 40-60% across the region. A more steadier period
looks to occur Monday night through much of Tuesday as PoPs further
increase to 60-80% areawide. Depending on the track, evolution and
timing of the low will determine how long rain lingers across the
area. Model guidance this afternoon continues to show the area of
low pressure lifting into the Great Lakes, then transferring its
energy to a strengthening coastal low that lifts northeast toward
New England. A rather potent upper-trough will drop southeastward
across the Great Lakes and possibly phase with the aforementioned
trough, supporting this strong area of low pressure. Will have to
monitor this system for some heavy rain potential, followed by some
gusty winds later Wednesday into Thursday.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE,
KRDG, KILG, KMIV, KACY and surrounding areas.

Tonight...For KRDG/KABE, MVFR CIGs give way to VFR CIGs by 21Z. For
KTTN/KPNE/KPHL/KILG, MVFR CIGs become VFR by 00Z. There may be a
brief period of rain that results in IFR conditions until 21Z, so
will carry TEMPO groups as confidence is low that it will occur. For
KMIV/KACY, rain continues into this evening. MVFR/IFR conditions
will not improve to VFR until at least 03Z. VFR thereafter. N-NW
winds around 10 kt, increasing to 10 to 15 kt with gusts up to 20 kt
late tonight. Moderate confidence overall, low confidence on timing.

Friday...VFR. W-NW winds 10 to 15 kt with gusts up to 20 kt,
increasing to 15 to 20 kt with 25 to 30 kt gusts late Friday
morning. High confidence.

Outlook...

Friday night...VFR/SKC. W-NW winds around 5-10 kt. High confidence.

Saturday...VFR early, with sub-VFR later in the day with isolated to
scattered rain showers. SW-W winds around 10-15 kt. Moderate
confidence.

Sunday...VFR expected under partly cloudy skies. Slight chance of
rain showers at night. W-NW winds around 15-20 kt. Moderate
confidence.

Monday and Tuesday...Sub-VFR expected with periods of light rain. E-
SE winds around 10 kt on Monday, becoming NE winds on Tuesday. Low
confidence.

&&

.MARINE...
Northwest winds 15 to 20 kt will ramp up to around 20 kt with 30 to
35 kt gusts late tonight into Friday morning. A Gale Warning remains
in effect, though gale gusts of 34 kt or higher may only occur for a
2 to 3 hour window late tonight. Will keep the Gale Warning in
effect, though best chances for gales will be on Delaware Bay and
the Delaware ocean waters.

On Friday, W-NW winds will range from 20 to 30 kt. A Small Craft
Advisory will be needed once the Gale Warning comes down.

VSBY restrictions in rain and fog until midnight or so, and then
conditions improve as rain ends.

Outlook...

Friday night...SCA conditions likely continue. W-NW winds around 15-
20 kt with gusts up to 25 kt. Seas of 3-5 feet.

Saturday through Sunday...No marine headlines expected. SW winds
around 10-20 kt on Saturday, becoming W-NW around 10-15 kt on
Sunday. Seas of 3-4 feet.

Monday through Tuesday...No marine headlines expected. NE-E winds
around 10-15 kt on Monday, becoming E-SE around 15-20 kt on Tuesday.
Seas of 2-4 feet.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Gale Warning until 10 AM EDT Friday for ANZ430-431-450>455.

&&

$$

SYNOPSIS...DeSilva/Staarmann
NEAR TERM...MPS
SHORT TERM...DeSilva
LONG TERM...Dodd/DeSilva
AVIATION...DeSilva/MPS
MARINE...DeSilva/MPS


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