Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 061149
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
649 AM EST Tue Dec 6 2022

.SYNOPSIS...
Rain showers will increase in coverage from west to east today due
to a series of low pressure systems impacting the area into
Wednesday. A trailing cold front will pass overhead Wednesday night
ahead of high pressure building on Thursday. An unsettled weather
pattern will occur beginning Friday and persist into early next
week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
Showers have now entered the eastern PA and Eastern Shores areas
and will continue to spread eastward across the forecast area
this morning. Heavier periods of rain expected beginning this
afternoon. Otherwise, no major changes from the previous
forecast discussion.

Broad weak low pressure system will take shape today, bringing
periods of rain today and tonight. Timing currently looks like some
lighter showers will arrive across eastern PA mainly after daybreak
this morning before steadier periods of rain will spread eastward
across the forecast area through late morning and into the afternoon
hours, continuing into the overnight hours. Low-level jet looks to
bring in best moisture feeds into the region during the afternoon
and nighttime hours, supporting our timeframe for the best chance
for the heaviest precip. Rainfall begins to wane by Wednesday
morning, with precip chances gradually diminishing through the day.
Temps will warm to the upper 40s to upper 50s this afternoon with
not much diurnal flux overnight as lows are expected to only drop
into the the low 40s and low 50s. Temps are slated to be a bit
warmer on Wednesday with less rain-cooled air, allowing high temps
to reach the low 50s to low 60s.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
The short term period Wednesday night through Thursday night will
feature zonal flow aloft as the polar and sub-tropical jet decouple
in the vicinity of the region. At the surface, high pressure will
remain in place north of the area with surface ridging nosing down
from the north. This will be the period in between systems this week.

A cold front will slide offshore early Wednesday evening. A few
showers may linger in the area Wednesday evening along the front or
early overnight (especially across Delmarva and far southern New
Jersey), but much of the area should dry out overnight. As the
cooler airmass and high pressure builds to our north, temperatures
will fall into the 40s in most locations. Skies should remain mostly
cloudy and a northerly wind will prevail around 5-10 mph.

On Thursday, northerly winds will prevail around 10 mph with some
gusts to around 20 mph possible. Despite the post-frontal regime,
temperatures will remain a few degrees above normal in the low to
mid 50s under mostly cloudy skies.

For Thursday night, the cooler airmass will begin to impinge more on
the region, especially north of I-95. It will remain mostly cloudy
with minimum temperatures ranging from around 30 degrees north to
near 40 degrees south and near the coasts. The GFS remains a bit of
an outlier and bullish with bringing precip into the area early
Friday morning. Given the dry airmass in place, this seems a bit too
aggressive. We`ve kept PoPs capped at slight chance for the predawn
hours as the best forcing won`t arrive until the daytime Friday.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
To summarize the extended period in short, there is vast uncertainty
with the timing of systems in and around our area into next week.

High pressure will be retreating to our north on Friday ahead of an
approaching low near the Midwest. Overall, there are still some
timing differences, but there is at least some agreement that Friday
night into Saturday will be wet. The GFS has been more aggressive
with the advancement of the precipitation shield beginning Friday
afternoon, giving us a wetter solution, whereas the ECMWF/GEM delay
the onset of precip until Friday night while giving us more
scattered precipitation. Due to timing differences, we have opted to
keep a high end chance of PoPs for this period. Temperatures will
remain close to average so most areas will see rain, although a few
snowflakes cannot be ruled out across northern areas into Saturday
morning as the high remains placed to our north.

As the low exits off our coast, Saturday afternoon and Sunday should
feature some drying. However, latest guidance suggests that
high pressure ridging over Quebec will again filter southward.
Repeatedly, the confidence here is quite low as some residual
moisture may hang around especially near the coast. Thus, we
cannot rule out the potential for showers to linger through
Sunday.

Into early next week, deterministic guidance has been fairly
consistent with a digging upper level trough across the Central US
and building upper level ridge into the Eastern US. To keep
continuity with the previous forecast, we have followed guidance
from NBM, with slight chance of PoPs for the remainder of the
period. Temperatures are expected to remain seasonal to slightly
above normal through the early portion of next week.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE,
KRDG, KILG, KMIV, KACY and surrounding areas.

Today...Ceilings have dropped to MVFR and IFR across much of the
terminals a couple hours ahead of schedule as rain has begun to
enter the region, spreading west to east this morning. The rain
will result in visibility restrictions, mainly later in the day
once heavier precip moves in. The lowest ceilings should occur
during the afternoon and at night with some LIFR possible,
especially for KABE/KRDG. East winds 5-10 knots gradually veer
southeast through the day. Low- level wind shear possible for
terminals along the I-95 corridor and points west. Medium
confidence.

Tonight...IFR likely w/ LIFR possible as rain and drizzle
becomes more widespread overnight. Fog development expected as
well. Ceiling and visibility restrictions expected through
early Wed morning. Southeast winds around 5-10 knots gradually
veer to the south. Medium confidence.

Outlook...

Wednesday...Early morning fog will likely be stubborn to burn
off through the day, leading to visibility restrictions. Very
gradual improvement Wednesday as rain moves out and clouds
gradually break up. South to southwest winds less than 10 knots,
becoming westerly at night. Low confidence.

Wednesday night...Any lingering restrictions should clear out
quickly in the evening. An isolated shower is possible early. Winds
shifting to the northwest then north around 5-10 kts. Moderate
confidence.

Thursday...VFR. Northerly winds around 10 knots with a few gusts
near 18 kts possible early. High confidence.

Thursday night...Mostly VFR, but ceilings will lower after 06Z
potentially to MVFR toward 12Z Friday. Winds north to northeast
around 5-10 kts. Low confidence.

Friday through Friday night...MVFR ceilings likely and IFR possible
with a chance of rain, especially later in the day and overnight.
Northeasterly winds 5-10 kts. Low confidence.

Saturday...Lingering restrictions possible along with a chance of
rain. Northeast winds 5-10 kts with gusts up to 20 kts possible. Low
confidence.

&&

.MARINE...
Southeast winds pick up to 15-20 kts Tuesday and Tuesday night
before diminishing Wednesday afternoon. Seas are forecasted to
build to 5-6 ft Tuesday night into Wednesday, warranting a Small
Craft Advisory for this timeframe.

Outlook...

Wednesday night...Marine headlines unlikely. Southwest winds early
shifting to the northwest and increasing to 10-15 kts. Seas
diminishing to around 3-4 feet early. A few showers possible along
with areas of fog possible early.

Thursday through Saturday...Small Craft Advisory conditions likely.
North to northeast winds prevailing around 15-20 kts with gusts up
to 25 kts at times. Seas increasing from 3-5 feet Thursday to 5-8
feet early Friday. Fair weather through Thursday night, then a
chance of rain through Saturday.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 9 PM this evening to 6 PM EST
     Wednesday for ANZ450>455.

&&

$$
SYNOPSIS...DeSilva
NEAR TERM...MJL
SHORT TERM...Staarmann
LONG TERM...DeSilva
AVIATION...MJL/Staarmann
MARINE...MJL/Staarmann


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