508
FXUS61 KCTP 181436
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1036 AM EDT Wed Sep 18 2024

.SYNOPSIS...
*Mostly cloudy with periods of light rain today into Thursday
 particularly over the south/eastern parts of central PA
*Little to no rainfall expected Friday into early next week
*Daytime temperatures peak +5-10 degrees above average Friday
 before trending seasonably cooler by early next week

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...
1030AM/1430UTC: Plenty of clouds covering central PA this
morning with areas of light rain drifting slowly northward
over the southern and eastern portions of the forecast area.
The most significant change to the previous near term forecast
was to increase POPs to 70-90+ percent in these areas based on
radar trends and latest hires model data. 12hr QPF amounts
remain below 0.25" through 00Z/8pm.

Previous Discussion Issued: 355 AM EDT Wed Sep 18 2024

MRMS and surface obs early this morning showed a few bands of
light rain pushing NWWD across the CWA and dissipating as they
approached the deeper/dry air in the lowest 7-8 kft AGL near
and to the north of Interstate 80.

We`re seeing a milder start compared to recent days with
daybreak temps ranging from the low and mid 50s over the
northern tier, to the low and mid 60s in the Lower Susq Valley.

Another few rounds of rain are expected later this morning and
this afternoon over the southern third of the state, where 2-3
tenths of an inch are possible by dusk. Locally higher amounts
near 0.50 of an inch are possible over the southern tier
counties, where some models indicate a bit of elevated
instability and the potential of a deeper warm cloud layer
and heavier showers in the 12-18Z time frame.

Elsewhere across Central and Northern PA, rainfall amounts will
be minimal, but widespread and generally thick mid level clouds
will persist with a light East to ENE breeze.

Afternoon highs today will be coolest (low to mid 60s) across
the Laurel Highlands and mainly between 70-75 degrees over the
remainder of the CWA.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH FRIDAY/...
The weak surface low off of the NC coast is progged to drift
northeast and out to sea tonight through the week`s end.

This will cause the low level flow to gradually back from the
ESE to the Northeast, allowing drier air to advect into the
much of the CWA late today and tonight.

An increasingly northerly flow should dry things out Thursday
into Friday. However, a few bands of enhanced mid-level FGEN
forcing just to the NW of the 1008 mb sfc low east of KACY will
help to focus the best chc for rain near and to the SE of the
I-81 corridor later tonight through Thursday night where an
additional few tenths of rain are expected.

Elsewhere, partial clearing of the mid and high cloud layer is
expected with just a few sprinkles or a stray brief shower
possible. Model RH profiles support an increasing amounts of
sunshine Thursday into Friday across much of Central and NW PA.
GEFS 850mb and surface temps indicate a return to above normal
afternoon readings.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Higher confidence in dry wx/no rainfall particularly early in
the period (through the upcoming weekend) thanks to deep layer
ridge pattern at the sfc and aloft. While model variability
remains elevated into next week, the ensemble means generally
favor weak upper troughing centered around the Great Lakes which
will support a marginal increase in rainfall/shower potential
along/ahead of an approaching front by next Monday or Tuesday.
Forecast max temps 75-80F peak +5-10F above mid/late September
climo to start the weekend and trend modestly cooler to 65-75F
(near the historical average) into early next week.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
MVFR ceilings at MDT with -SHRA with otherwise VFR conditions
prevailing as of 10Z observations. Rain showers originally
progged to go into JST have mostly fallen apart so have limited
VCSH mentions until closer to 13-14Z. GLAMP guidance continues
to go heavy on the low-level clouds and given model agreement
can see a period between 13Z-16Z where JST/AOO experience lower
ceilings with slightly higher confidence in the 14Z-16Z
timeframe. RAP model soundings continue to outline this threat
longer into 20Z which matches fairly well with GLAMP guidance so
have continued restrictions through ~20Z Wednesday at these
airfields.

Showers closer to MDT/LNS will remain scattered this morning so
have mainly left mentions to VCSH with lower ceilings in the
near-term through 17Z where the best chances for rainfall will
be today. Model guidance has hinted that -SHRA/-RA will return
later in the afternoon/evening at MDT/LNS; however, there is
lower confidence in this solution with some model spread. The
12Z TAF package does not make overly explicit mentions of
showers, even in the form of VCSH, at MDT due to increased
uncertainty here but have outlined VCSH at LNS due to closer
proximity to moisture.

For airfields further north (BFD/IPT/UNV) have limited
precipitation mentions to UNV throughout the TAF period as there
is considerable uncertainty on rainfall pushing closer to the
Interstate 80 corridor. GLAMP guidance suggests MVFR ceilings at
UNV from 12Z-20Z; however, RAP model soundings suggest slightly
less clouds cover in the lower-levels so have kept cloud bases
slightly below MVFR thresholds in a targeted timeframe between
16-18Z, where -SHRA might trek closer to the airfield. In the
overnight period (00Z-12Z Thursday), GLAMP guidance suggests fog
formation at BFD/IPT but given some cloud cover and light winds
have decided to keep these restrictions out of the TAF.

Outlook...

Thu...MVFR cigs possible in the southern and eastern portions of
the airspace.

Fri-Sun...Valley fog in the morning; otherwise VFR/no sig wx.

&&

.CLIMATE...
The first day of Autumn 2024 (Fall Equinox) begins at 8:44 am
EDT on September 22nd.

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Lambert/Fitzgerald/Steinbugl
SHORT TERM...Lambert/DeVoir/Fitzgerald
LONG TERM...Fitzgerald/Steinbugl
AVIATION...NPB
CLIMATE...NPB