Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 281335
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
935 AM EDT Thu Mar 28 2024

.SYNOPSIS...
Low pressure along the Carolina coast will track northeast and
out to sea today. High pressure will briefly build into
Pennsylvania tonight and Friday, then a weak area of low
pressure approaching from the midwest will pass across the
state Saturday. A more significant low is likely to track just
north of Pennsylvania through the Eastern Great Lakes early next
week.

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...
Spotty light rain is brushing far southeast York and Lancaster
Counties this morning, but CAMs and radar trends indicate the
light rain will expand farther west by late morning to roughly
include an Adams to Schuylkill County corridor. Made minor
adjustments to POPs and sensible weather for this. But the
overall message remains that the most significant rain from this
system will remain east of the forecast area. Model soundings
and surface obs will still support the possibility of some
lingering very light rain or drizzle across parts of the Lower
Susq Valley through late morning. The passage of a cold front
and arrival of a drier northwest flow should result in a
diminishing chance of measurable rain over the southeast
counties by early afternoon.


Latest guidance tracks a developing surface low on the front
well east of PA later today, keeping rain east of the forecast
area this afternoon. A much drier northwest flow behind the
cold front will result in brightening skies from west to east
today. However, model RH profiles indicate warm advection aloft
ahead of the approaching upper trough will result in a lingering
veil of high clouds over Central and Eastern PA.

GEFS 2m temp anomalies point to near seasonal highs today,
ranging from the upper 40s over the Alleghenies, to the low 50s
east of the mountains. Forecast soundings over the central and
western counties shows a marked dry layer above a weak inversion
later today, a signature that usually supports undercutting NBM
dewpoints a few degrees.

&&

.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Fair and seasonable weather is anticipated tonight, as the
upper trough shifts east of the state. However, a weak area of
low pressure diving across the Ohio Valley could potentially
come close enough to produce a few snow showers over Southern
Somerset County.

Large scale subsidence behind the exiting trough should result
in sunny, breezy and seasonable weather Friday. Mixing down
model 850mb temps of around -1C to -4C translates to expected
highs ranging from the mid 40s over the N Mtns, to the mid and
upper 50s across the Lower Susq Valley. Bufkit soundings also
support wgusts several knots above NBM guidance Friday
afternoon and dewpoints a few degrees below due to fairly deep
mixing. Higher fuel moistures should limit the risk of wildfire
spread, despite expected wind gusts near 30kt and RH falling to
around 30pct.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
A weak wave of low pressure tracking across PA could produce a
bit of light rain Sat or Sat night. Beyond that, a somewhat more
substantial rainfall is possible early next week associated
with a stronger low approaching from the midwest.

&&

.AVIATION /13Z THURSDAY THROUGH MONDAY/...
Areas of LIFR and brief VLIFR will continue across the Lower
Susq Valley and Western Pocono airfields through the mid morning
(12-13Z) before slowly improving to MVFR late this monring. MVFR
conditions (related to CIG bases) could linger until at least
the mid afternoon hours before lifting to bkn VFR Stratocu cloud
bases.

Current MVFR cigs at KIPT (where the cold front just pushed
trough around 08Z) will improve to VFR between 16-17Z. A
similar, albeit slightly faster progression from borderline
IFR/MVFR cigs (in cooler/moist upslope flow at the KBFD and
KJST airfields), to late morning VFR will occur.

Elsewhere across the Central Ridge and Valley Region of the
state (that was firmly in the wake of the cold front), mainly
VFR will occur, though there could be some periods of high end
MVFR CIGS through Noon EDT (16Z).

Mainly VFR will follow for later this afternoon into Friday as
a weak sfc ridge of high pressure builds over the Commonwealth.
The is a low end probability for a few periods of MVFR cigs
redeveloping late tonight at KJST and KBFD.

As an area of surface low pressure intensifies fairly quickly
well east of the NJ Coast tonight, NW wind will increase with
likely gusts into the low to mid 20s. Borderline LLWS at all TAF
sites tonight with the base of 35KT NW winds between 1.5 and 2
kft AGL. Leaning toward some mixing of the NW wind to smooth out
the vertical gradient of the wind profile and create more of a
turbulent low-level mechanical mixing profile compared to true
LLWS with a +/-20KT change over 200 FT in the verticaL.

Outlook...

Fri...Patchy MVFR cigs possible early across the Western Mtns
of PA, otherwise VFR with a moderately gusty (20-25 mph) NW
winds.

Sat-Mon...Multiple rounds of showers with a period of dry
weather Sunday afternoon.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...DeVoir/Fitzgerald
NEAR TERM...DeVoir/Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...Gartner/Colbert
AVIATION...Lambert


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