North Star, Delaware 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

858
FXUS61 KPHI 212046
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
346 PM EST Thu Nov 21 2024

.SYNOPSIS...
Low pressure developing off the coast this afternoon will
retrograde north and west tonight into Friday as it gets
captured by an upper level low. The low will linger near the
area through Friday then gradually move away through the
weekend. Weak high pressure briefly arrives for later Sunday and
Monday, followed by a cold front Monday night into Tuesday. A
low pressure system may affect the area around the Thanksgiving
Day timeframe.

&&

.NEAR TERM /THROUGH FRIDAY/...
First measurable snowfall event of the season expected tonight
through early Friday across portions of the region. Winter Storm
Warnings and Winter Weather Advisories are in effect.

A large closed upper low pressure system will pass from the
southern Great Lakes this evening toward the upper Mid-Atlantic
and southern New England by late Friday. At the surface,
strengthening low pressure offshore of New Jersey will lift
north into southern New England tonight, then retrograde back
into eastern Pennsylvania by Friday afternoon.

A stratiform precipitation shield has developed across New
Jersey and eastern Pennsylvania today. This will lift north with
the low pressure this evening, likely resulting in a cessation
of rainfall across much of the area south of I-78 for several
hours tonight. Meanwhile, dynamic cooling will result in a
change over from rain to snow across much of the higher
elevations. This has already begun across the Pocono Plateau,
with some light accumulations already beginning in grassy areas
as of 3 PM. A change over to snow will occur into northwestern
New Jersey late this evening, with mostly snow expected by
midnight across elevations over 1,200 feet.

As the precipitation shield shifts back toward the south around
daybreak Friday, dynamic cooling conditions will also shift
south resulting in a change over to snow south into the Lehigh
Valley, Berks County, and even as far south as the Philly metro
area. The limiting factor for accumulating snowfall outside of
the higher elevations up north will be the surface temperatures
and southwest winds. Temperatures likely hovering in the mid
30s much of the night won`t support much if any accumulation
outside of the higher terrain. However if a heavier band of
precip can develop and pivot southward, the heavy rate of
snowfall, dynamic cooling, and little to no solar insolation
could be sufficient to produce a slushy coating in grassy and
elevated surfaces early in the morning, perhaps even as much as
1 to 2 inches in the higher elevations in Berks and Lehigh
Counties.

The Winter Storm Warning remains in effect as previously issued
for Carbon and Monroe Counties. Total snow accumulations
between 6 and 10 inches above 1,200 feet in elevation and
between 1 to 4 inches below 1,200 feet in elevation within the
warning area. Winds gusting as high as 35 mph. A new Winter
Weather Advisory was issued for Sussex (NJ), Morris, Warren, and
Northampton Counties. Total snow accumulations generally
between 1 and 3 inches within the advisory area. Greatest snow
accumulations at elevations over 1,200 feet, with totals near 4
to 6 inches possible.

The snow should switch back to mostly rain outside of the higher
elevations before tapering off into Friday afternoon and
evening. Expect high temperatures ranging from near 40 degrees
to the mid 40s near the coast. South to southwest winds 10-15
mph with gusts near 25-30 mph possible. A rather raw and winter
like day to be sure.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
The closed upper low and surface low will depart and strengthen
offshore into the weekend. This will place us on the fringe of a
tight pressure gradient with high pressure settling to our
southwest. This will result in dry, but seasonably cool and
breezy conditions Friday night through Sunday.

Any lingering light rain or snow will taper off by late Friday
evening. Expect highs generally ranging from the upper 40s to
mid 50s Saturday and Sunday. Lows Friday night in the low to mid
30s, and in the mid 30s to near 40 degrees Saturday night. West
to northwest winds 10-15 mph through the period (including at
night) with gusts near 20-30 mph possible during the daytime
periods. Partly to mostly cloudy skies.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Low pressure in the upper levels will slowly drift away from
the region as it continues to move east through Atlantic Canada
Sunday night through Monday. This will allow for a brief period
of ridging to move in bringing dry and tranquil weather. Lows
Sunday night will generally range from the upper 20s to the mid
30s with highs Monday mainly in the 50s except for some low 60s
over our southern most zones in Delmarva and some 40s over the
southern Poconos.

The next system will affect the area Monday night into Tuesday
as an upper level trough and associated surface low move
eastward through Ontario into Quebec. This will drag a cold
front through the area with some showers mainly for the Monday
night into early Tuesday time frame. This system will be
relatively moisture starved so not expecting large precip
amounts. Tuesday will still be relatively mild with high
temperatures similar to Monday but will be followed by colder
but dry weather for Wednesday as high pressure briefly returns.
Expect highs Wednesday mainly in the 40s to around 50 except 30s
in the Poconos.

As we turn our attention to the end of next week, most of our
available model guidance indicates a low pressure system
developing and affecting the east coast around about
Thanksgiving Day into that night. However given that this is a
week out, there is lots of uncertainty regarding the system`s
strength, track, and overall evolution including timing. The
track will help determine precip type (rain, snow, or a mix) but
it`s worth mentioning this looks like a setup where there won`t
be a strong, cold antecedent high. Therefore, currently not
looking like the best setup for a major snowstorm in the urban
corridor.

&&

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

Rest of this afternoon...MVFR/VFR ceilings. Some rain lifting
northward will result in MVFR visibilities at times. Some
improvement to VFR from the south, especially near and
south/east of KPHL. Northwest to west-northwest winds 8-12
knots, however some local gusts to 20 knots. Low confidence
regarding the details of flight category changes.

Tonight...Ceilings mainly between MVFR and VFR. Some rain
around especially north and west of KPHL. The rain mixes with
and changes to snow closer to daybreak at KABE and KRDG. West-
northwest to west winds around 10 knots, which may gust up to 20
knots at times. Low confidence regarding the details flight
category changes.

Friday...Ceilings lower to MVFR/IFR with a round of rain
pivoting across the area, especially from the I-95 terminals to
the north and west. A period of snow at KABE and KRDG with
IFR/LIFR visibilities. The rain could mix with some west snow
into the I-95 terminals. West- southwest winds 10-15 knots with
some gusts 20-25 knots, which should diminish some in the
afternoon. Low confidence.


Outlook...

Sunday night through Tuesday...VFR with no significant weather
through the day Monday. Some showers and associated restrictions
will be possible for a time Monday night into early Tuesday.

&&

.MARINE...
Conditions will remain at Small Craft Advisory criteria through
Friday, with a few periods of winds gusting to near gale force
across the ocean waters. Westerly winds shifting southwest on
Friday near 20-30 kts. Seas 4-6 feet. Small Craft Advisory
remains in effect for Delaware Bay and a Gale Warning remains in
effect for all Atlantic coastal waters through Friday.

Outlook...

Friday night through Sunday...Small Craft Advisory criteria
conditions expected. West to northwest winds 20-25 kts with
gusts up to 30 kts and seas 3-6 feet. Gale force wind gusts may
linger into the first half of Friday night near Delaware Bay.

Sunday night through Monday...The conditions are anticipated to
be below Small Craft Advisory criteria.

Tuesday...Small Craft Advisory conditions may develop behind a
cold front.


&&

.CLIMATE...
Driest autumn (Sep-Nov) on record, and any 3-calendar month
period on record, plus current status:

                   9/1-11/20   Driest          Driest 3         Year/
Site              2024 precip  Autumn Year  Calendar months    months
Allentown (ABE)       1.96      3.81  1922      3.58        Oct-Dec 1928
A.C. Airport (ACY)    1.01      3.34  2001      2.35        Oct-Dec 1946
A.C. Marina (55N)     0.79      2.89  1941      2.52        Aug-Oct 1895
Georgetown (GED)      1.17      2.67  2001      2.20        Aug-Oct 2024
Mount Pocono (MPO)    3.35      4.21  1931      3.36        Oct-Dec 1928
Philadelphia (PHL)    1.66      2.37  1922      2.37        Sep-Nov 1922
Reading (RDG)         1.96      2.89  1922      2.89        Sep-Nov 1922
Trenton (TTN)         0.79      3.18  1922      2.66        Jun-Aug 1966
Wilmington (ILG)      1.49      3.17  1922      3.17        Sep-Nov 1922

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory from 7 PM this evening to 10 AM EST
     Friday for PAZ062.
     Winter Storm Warning until 4 PM EST Friday for PAZ054-055.
NJ...Winter Weather Advisory from 7 PM this evening to 10 AM EST
     Friday for NJZ001-007-008.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 PM EST Friday for ANZ430-431.
     Gale Warning until 6 PM EST Friday for ANZ450>455.

&&

$$

SYNOPSIS...Fitzsimmons
NEAR TERM...Staarmann
SHORT TERM...Staarmann
LONG TERM...Fitzsimmons
AVIATION...Gorse
MARINE...Fitzsimmons/Staarmann
CLIMATE...RCM