120
FXUS61 KCTP 050322
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1122 PM EDT Fri Apr 4 2025

.SYNOPSIS...
*Periods of showers will last through the weekend
*Unseasonably cold temperatures to start early next week with
 rain and snow showers downwind of Lake Erie

&&

.NEAR TERM /THROUGH SATURDAY/...
First round of showers returned to central PA this evening and
max coverage is pushing into eastern PA late this evening, with
lingering showers over the Laurel Highlands and N Central
Mountains. CAMs dissipate these over the next few hours as next
wave over the Ohio Valley approaches overnight, and spread
higher POPs from W->E overnight and into Saturday morning. This
as isentropic lift increases on the nose of 40-50kt LLJ from
the west/southwest. The strong moisture flux will drive higher
PW and a plume of elevated instability into western PA and could
result in some brief heavy downpours into the predawn hours
Saturday.

CAMs indicate timing of heaviest rainfall (0.25-0.50+") in the
09-12Z timeframe focused over the NW Alleghenies with GT 50%
chance of 1"+ there. It will be another very mild night vs.
early April climo with min temps fcst in the 40-50F range or
+10-20F above the historical average.

No sig changes heading through Saturday with the lead surface
low/frontal wave progged to track northeast across Lake Erie
and Ontario on Saturday.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
Periods of showers will cross central PA in waves Saturday night
and SUnday along the trailing frontal zone which will move very
slowly to the southeast overnight Saturday into Sunday. Fgen
forcing beneath the right entrance of a jet streak over the Grt
Lks will likely result in lingering light post- frontal
precipitation on Sunday as cooler air starts to filter into the
region from the NW. Model soundings indicate it could become
cold enough for a light rain/wet snow mix over the northern tier
elevations where a light accum <0.5" can`t be ruled out prior
to daybreak Monday.

EPS plumes and WPC/NBM blends support rainfall Sat-Sat night
ranging from 1-1.5 inches over the northern half of the CWA
with ~0.25" fcst in the Lower Susq Valley. The southern portion
of the area remains on the eastern/northern periphery of the D2
and D3 MRGL svr tstm risk areas from SPC with a couple of strong
storms possible.

Cloud cover, precipitation and low level cold advection should
make for a markedly colder end to the weekend over the western
part of the CWA with 24hr maxT deltas of -10 to -30F. This will
set the stage for a rather chilly to unseasonably cold start to
next week.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
By daybreak Monday and lingering rain showers from the cold
front sliding southeast of Pennsylvania should be dissipating.
Skies will remain partly to mostly cloudy throughout the day,
but areas in northwest PA should have a few breaks in the clouds
to provide some sunshine. Model data favors a period of dry
weather during the day on Monday with noticeably cooler max
temps (~55F) over the southern tier of CPA (-10 to -15 degrees
cooler vs. Sunday).

The focus will shift to a cold upper trough digging through the
Great Lakes into the Northeast Monday night into Tuesday. This
feature should bring unseasonably cold temps (-15 to -25F below
the historical average) and unsettled wx with rain/snow showers
likely along with some potential for strong blustery wind gusts.
The colder cyclonic/NW flow should linger snow showers downwind
of Lake Erie over the Allegheny Plateau into Tuesday night and
possibly Wednesday morning. Temps should hit their lowest this
week Tuesday into Tuesday night.

There are some long range model signals that suggest upper
level troughing will reload and dig into the Ohio Valley region
into the second half of next week. There remains some spread in
the long range ensembles as to the strength of this troughing,
but the signals are there. This pattern would favor a
continuation of temps below the historical average for the
second week of April.

There may also be an opportunity for frost/freeze conditions as
the spring growing season gets underway in the Lower Susquehanna
Valley. Given the southeasterly flow expected for Thursday
morning, colder temps, and skies expected to be mostly clear to
partly cloudy, a mention of frost has been included in the
forecast for Thursday.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
1029 mb surface high ridging south from Quebec Canada into
Eastern PA will maintain generally dry conditions and relatively
higher cloud bases (generally VFR conditions through 10Z
Saturday). In contrast, a nearly north/south inverted trough far
western PA will pool somewhat higher sfc dewpoints and lower
cigs with several periods of mainly light rain/showers at
Central and Western PA Airfields overnight.

The transition down through MVFR will occur after 07-09Z Sat
from KUNV north and east as the llvl east/southeasterly flow
freshens and notable southerly LLJ of 40-45 KTS (with LLWS)
develops during the early to mid morning hours of Saturday and
persists through the mid to late afternoon hours Saturday.

The upward vertical motion created by the llvl warm advection
from this strengthening southerly flow will create/enhance areas
of light to moderate rain with all areas by 12Z Sat seeing
mainly between 80 and 100 percent chances for rain.

Cigs Saturday will fluctuate between lower end MVFR and IFR with
mainly MVFR vsbys.

Previous Discussion with still valid details of Saturday`s
conditions...

After a lull in precip today, the boundary that crossed as a
cold front yesterday will return as a warm front, overspreading
lowering cigs and another round of showers and storms later
tonight into Saturday. Most sites will see a decrease of cigs
to IFR by daybreak Saturday. Model consensus currently holds
ceilings bottoming out between 500-1000ft, however a brief
period of LIFR can`t be ruled out given the strong warm air
advection expected in the early morning hours. Marginal LLWS is
also expected late tonight into early Sat morning across mainly
the northern and western TAF sites. Rain will persist through
Saturday while we remain in the warm sector. After 00Z Sunday
the cold front is expected to push across the state.
Precipitation will begin diminishing behind the front through
Sunday morning, but with lowering temperatures its possible a
brief snow shower could impact sites in the northwest.

Outlook...

Sat...Widespread showers and thunderstorms; impacts likely.

Sun...Lingering rain/snow showers; restrictions poss especially
N/W.

Mon-Tue...Restrictions likely NW Mtns. Snow showers possible.

&&

.HYDROLOGY...
Forecast rainfall through the weekend ranges from around 0.75
inches in the Lower Susquehanna Valley to ~2 inches across
parts of the NW Alleghenies. No river flooding is forecast at
this time. The Conewango Creek at Russell is forecast to barely
exceed action stage/7ft level on Monday. The West Branch
Susquehanna at Williamsport may get close to the 10ft action
stage by Monday.

&&

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

&&

$$

SYNOPSIS...DeVoir/Steinbugl
NEAR TERM...DeVoir/Steinbugl
SHORT TERM...DeVoir/Fitzgerald/Steinbugl
LONG TERM...Lambert/Steinbugl/Bowen
AVIATION...Lambert/Bowen
HYDROLOGY...Steinbugl