322
FXUS61 KPHI 121345
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
945 AM EDT Wed Mar 12 2025

.SYNOPSIS...
High pressure extends southward into the Mid-Atlantic through
Friday. A warm front lifts north through the region Friday
night, and then a strong cold front passes through the region
Sunday night. High pressure returns for the start of the new
work week.

&&

.NEAR TERM /THROUGH TONIGHT/...
930 AM...Minor tweaks made to the forecast this morning
especially in the dew point category. Dew points are very dry,
mainly in the teens in wake of the cold front that passed
through. This has resulted in lower RHs this morning, but
overall has had little impact on the area at this time.
Previous discussion remains below:

Cooler conditions expected today under partly to mostly cloudy
skies with a dry northeast to easterly breeze.

Zonal flow pattern will continue to prevail aloft through mid
week. At the surface, Canadian high pressure will build into New
England in the wake of a cold front. Surface ridging should
remain fairly weak until tonight, when surface pressure rises
become more substantial. This will have implications for the
temperature forecast today.

The challenge for today`s forecast will be temperatures. Given
the lack of surface ridging extending southwest into the area
until later tonight, this would support temperatures over
performing again today despite a light northeast to east surface
flow. The core of the Canadian airmass will remain displaced
well northeast of our local area, which should allow
temperatures to rise fairly substantially by midday. However,
the limiting factor will be mid level cloud cover. This should
be confined to roughly the northern half of the area, and
retreating northward into the afternoon. Long story short, a lot
of factors at play with today`s temperature forecast. The
ultimate result will be the warmest temperatures occurring
southwest into western Delmarva and coolest north and east
closer to the colder airmass and closer to the coast. Should
generally see widespread high temperatures in the 50s. Inland
areas near and south and west of the Philly metro will reach
near 60 degrees, while the immediate coast and higher terrain up
north will be stuck in the 40s.

As mentioned previously, there will be periods of clouds and
sun today with more sun to the south and more cloudy than not
farther north. Winds will be from the northeast shifting to east
or southeast around 5-15 mph, with some gusts near 25-30 mph
possible near the coasts.

Surface ridging will become more entrenched across the region
into tonight. This will push the marine layer well inland, which
should keep temperatures relatively mild and generally above
normal in the mid 30s to near 40 degrees for most areas. We
should also see marine stratus advecting inland overnight with
mostly cloudy to overcast skies by dawn Thursday. Some fog is
possible near the coasts, but the airmass is very dry, so fog
develop will probably be a struggle tonight. Mainly a stratus
setup.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
High pressure sets up over eastern Canada for the short term
forecast period, and the base of the high will extend down
through the Northeast. A northeast flow sets up, and this allows
for a cooler, yet still a few degrees above normal for this
time of the year, airmass to spread into the local area. Highs
will generally be in the 50s on Thursday, then a couple of
degrees warmer on Friday.

Some patchy fog and drizzle may develop Thursday night, most
likely along the coastal plain of New Jersey and in Delmarva,
with the onshore flow. As the high lifts away Friday night, a
warm front extending from strong low pressure over Northern and
Central Plains and Upper Midwest lifts north through the Mid-
Atlantic and Northeast. Onshore flow persists, and with
increasing low level moisture, more patchy fog and patchy
drizzle will develop across the region late Friday night and
into early Saturday morning.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Cold front moves through the Great Lakes and into the Ohio
Valley on Saturday. Some shortwave energy may spin off ahead of
the system to spark off some showers Saturday afternoon and
evening. Otherwise, warm air advection develops due to strong
southerly flow. Highs climb into the 60s for most of the area
and into the low 70s for Delmarva. Turning fairly humid for mid-
March as well with surface dew points into the low to mid 50s
in most areas.

Pressure gradient between approaching cold front and high
pressure over the western Atlantic tightens further on Sunday,
combined with a strong low level jet will allow south winds to
increase to 15 to 25 mph with 30 to 40 mph gusts.

The timing of the passage of the front is still in question.
Latest guidance has reverted to more of a Sunday night time
frame. Model sounding profiles remain unimpressive with low-
level 0-3 km lapse rates less than 6 degrees C/km, due to a warm
700-850 mb layer with the strong WAA. However, some elevated
instability remains possible and guidance continues to forecast
55 to 65 kt of 0-6 km Bulk Shear. Therefore, Sunday is still
shaping up to be a low CAPE/high shear day in which convection
could be limited, but any storms that develop could be strong to
severe. This front does look to bring much needed and
beneficial rainfall. With PWATs close to 1.5 inches, however,
localized heavy rain and poor drainage flooding are possible.
Will include a chance for thunderstorms in the forecast Sunday
afternoon and evening.

Showers taper off from west to east Sunday night. Depending on
how far east the front gets, some showers may linger along the
coast into Monday morning. Turning cooler with highs in the mid
and upper 50s on Monday, which are still above normal for this
time of the year, when a few degrees warmer on Tuesday.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...VFR with SCT/BKN mid to high level ceilings. Northeast
wind 5-10 kt for most locations shifting to east during the
afternoon and eventually southeast towards 00Z. During the
afternoon hours KMIV/KACY could see a few wind gusts of 15-20
kt. High confidence.

Tonight...Sub-VFR conditions with low stratus clouds. Rain
showers are also possible especially near KABE.

Outlook...

Thursday through Saturday...Sub-VFR conditions in low clouds
and fog, with some improvement at times.

Sunday...Sub-VFR conditions likely at all terminals,
particularly during the afternoon hours within periods of SHRA
and embedded TSRA.

&&

.MARINE...
Northeast to east winds increasing to around 15-20 kt with
gusts up to 25 kt at times and seas building to 4-6 feet across
the Atlantic waters. The Small Craft Advisory was expanded to
include all Atlantic coastal waters, which is in effect now into
Thursday. Fair weather.

Outlook...

Thursday through Friday...Seas remain around 5 to 6 feet on the
ocean waters, subsiding on Friday. The Small Craft Advisory in
place continues for Thursday and will likely need to be extended
into Thursday night and possibly into daytime Friday as well.
VSBY restrictions in fog possible at night and in the morning,
especially along the coasts.

Friday night and Saturday...Sub-SCA conditions through early
Saturday, but winds and seas begin to increase by Saturday
evening, with SCA conditions Saturday night.

Sunday...Mainly SCA conditions but a period of Gale force winds
likely. VSBY restrictions in afternoon showers. Scattered
thunderstorms possible.

&&

.FIRE WEATHER...
With lighter winds expected inland today, fire weather
conditions are less of a concern than previous days. However,
minimum relative humidity values will remain in the 20-35%
range with a northeast to easterly breeze remaining near 10-15
mph. The stronger winds will coincide with higher RH values, and
lighter winds with lower RH values. Therefore, not planning any
fire danger statements for today.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 PM EDT Thursday for ANZ450>455.

&&

$$

SYNOPSIS...AKL/MPS
NEAR TERM...DeSilva/Staarmann
SHORT TERM...AKL/MPS
LONG TERM...AKL/MPS
AVIATION...Cooper/DeSilva
MARINE...AKL/DeSilva/Staarmann
FIRE WEATHER...WFO PHI