Latest Area Forecast Discussion for Central PA

Here is the latest Area Forecast Discussion for Central PA

This text statement is the latest forecast reasoning from the NWS in State College, PA

See the links at the bottom of the page for previous issuances/versions of the statement as well as our other text statements.

780
FXUS61 KCTP 220233
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1033 PM EDT Wed May 21 2025

.SYNOPSIS...
* An unseasonably cool and wet stretch of weather will continue
with periods of rain through the end of the week
* Daytime temperatures will be 10 to 20 degrees below the
historical average through Saturday with no signs of a
summertime warmup on the horizon
* Marginal improvement/minimum chance of rain by the end of
Memorial Day weekend; cool/wet pattern persists next week

&&

.NEAR TERM /THROUGH THURSDAY/...
The stubborn upper troughing pattern continues across the
northeast US, which will continue to bring cloud, cool, and wet
weather to the Commonwealth through Memorial Day weekend. For
tonight, an occluded surface low and associated upper level low
will continue to shift east into Pennsylvania bringing periods
of light to moderate rain showers. Fortunately, cold air damming
kept instability to a minimum Wednesday afternoon and limited
the amount of heavy rainfall in particularly vulnerable areas of
southwest PA. The flood risk is basically over at this point,
with any rain showers only causing some minor ponding overnight.

By daybreak Thursday, temperatures won`t fall much from where
they are currently. Lows in the mid 40s in the northeast and low
50s along the Mason Dixon Line seem like a good bet. During the
day Thursday, the surface and upper low will traverse over
Central PA, bringing more widespread showers to the region.
Southeast flow ahead of the system will keep cold air dammed
east of the mountains and lead to another anomalously chilly/raw
day. Highs will likely stay stuck in the 50s everywhere, which
is 15 to 20 degrees below normal for this time of year.

Additional rainfall tonight through Thursday will range from
half an inch to an inch and a quarter, with most of it being
beneficial. This pattern should continue to erode away at
drought conditions and rainfall deficits across southeast PA. In
fact, much of southeast PA is running rainfall surpluses of 2-3"
in the last 30 days and 90-day anomalies (since late February)
are now back to near normal.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
Pinwheeling double-barrell sfc lows beneath a large scale
cyclonic upper flow/trough will maintain the cool and wet
pattern into the weekend. Expect frequent periods of
rain/showers with unseasonably cool daytime temps in the 50-60F
range or 10 to 20 degrees below the historical average for late
May.

Despite the persistent upper trough, surface forcing will wane
somewhat Friday and Saturday as flow shifts out of the west and
northwest. This will usher in slightly lower PWATs and a lesser
chance for rainfall. That being said, cool temps aloft will
still support scattered showers and cloudy conditions. We may
see some improvement in southeast PA by Saturday afternoon with
a few breaks in the clouds thanks to downsloping northwest flow,
but cool temps and mostly cloudy skies are a good bet.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
If you squint really hard at the upper air charts for Sunday,
you might be able to convince yourself that upper level flow is
becoming slightly less trough-y, but that`s probably just
wishful thinking. We are growing less optimistic to see any
marked improvement before Monday. The recent blocking pattern
has proven to be rather persistent and in no hurry to unravel.
The cyclonic flow and cool temps aloft should translate into a
good deal of cloud cover with POPs peaking during the afternoon
hours coincident with diurnal heating.

Precip probs should bottom on Monday before ramping higher into
Tuesday-Wednesday. Models are coming into better agreement in
tracking the southern stream wave farther to the north. There
are even signs that the briefly split-stream flow will try to
close off into another upper low in the Great Lakes/Ohio Valley
region by the middle of next week. So it appears the cool and
wet pattern will continue into the end of the month with no
signs of summer weather on the horizon (meteorological summer
begins on June 1).

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Rain showers are overspreading much of central Pennsylvania as
of 00Z. All sites are currently a mix between MVFR and IFR
flight categories, mainly due to lowering CIGS and heavy rain.
Expect CIGS to remain low overnight, and into tomorrow.

Expect showers on Thursday to be a bit less widespread.
Confidence is still high in rainfall across the state for much
of the day (80%). IFR to MVFR conditions will prevail into at
least Friday, as the low pressure system stalls over the lower
Great Lakes. Little is anticipated in the way of VFR
improvements, however there could be brief breaks on Thursday
which could see some VFR across the southeast with around 20%
confidence in any VFR prevailing more than an hour.

Some improvement over the weekend, as the low reforms off
the east coast, but still a chance of showers each day into
early next week.

Outlook...

Fri...Ocnl SHRA.

Sat-Mon...Still a chance of a shower.

&&

.HYDROLOGY...
Flood Watch was cancelled early as the heavy rainfall rates
never materialized in Somerset or Bedford County (thankfully).
Scattered showers overnight will bring additional light to
moderate rainfall with an additional 0.5 to 1.25" expected
through Friday evening.

Only 3 points are now fcst to exceed action/caution stage:

-Confluence (just above 7ft action stage)
-Williamsport (just under 12ft or ~1.5ft above action stage)
-Beech Creek (~0.1ft over action level)

Juniata basin points were lowered below action stage along with
lower Susquehanna Basin tribs.

&&

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

&&

$$

SYNOPSIS...Steinbugl/Banghoff
NEAR TERM...Banghoff
SHORT TERM...Steinbugl/Banghoff
LONG TERM...Steinbugl/Banghoff
AVIATION...Martin/Bowen
HYDROLOGY...Steinbugl/Banghoff

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