NWS Forecast Discussion
568
FXUS61 KCTP 211609
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
1209 PM EDT Tue Jul 21 2026
.WHAT HAS CHANGED...
* No significant changes at this time.
&&
.KEY MESSAGES...
1) Scattered to numerous severe thunderstorms are expected this
afternoon through the evening hours today.
&&
.DISCUSSION...
KEY MESSAGE 1: Scattered to numerous severe thunderstorms are
expected this afternoon through the evening hours today.
We are in standby mode for now as the copious amount of
energy/lift/strong upper level diffluent flow (associated with
the left exit region of a 100+ KT jet) has produced an
expansive area of weak convection embedded in light to moderate
rain. All of this thick/debris cloud cover will prevent deep
convection through the early afternoon, but pockets of fairly
quick destabilization via breaks of sun should spread into
western PA and remain over our far SE zones to trigger some
deeper convection by or shortly after 18Z.
We`ll be closely monitoring satellite trends and meso-B
stability and shear fields to better hone in on areas under the
gun for potential impact of fast-moving TSRA.
Previous Disc...
Thunderstorms are expected to develop ahead of an eastward-
moving cold front across the Ohio Valley and along a pre-
frontal trough crossing the CWA between roughly 2-9PM. No
changes were made to the level 3/5 enhanced risk area from SPC
for day 1 with swaths of damaging wind gusts remaining the
primary hazard. Diurnal heating within cloud breaks, combined
with upper 60s to lower 70s dewpoints, will support moderate
surface-based instability across the broad pre-frontal warm
sector. The most favorable overlap of this instability and 40-50
kt of effective shear is expected to foster a mix of organized
clusters and supercells that should evolve and spread eastward
through the day. Severe hail and a few tornadoes will also be
possible with any sustained supercells. The enhanced level 3/5
risk favors a higher confidence/coverage in severe storms with a
few significant severe storms possible reaching intensity
levels (75+ mph wind gusts and/or EF-2 tornado) we may only
experience 1x or 2x/year.
WPC has expanded the level 2/4 excessive rainfall outlook to
cover the majority of the CWA. However, despite plenty of juice
and high PWATs supportive of locally intense rain rates,
overall confidence is low/limited by the lack of a hires model
signal and relatively fast/progressive storm motions. Opted to
pass on a FF watch for this cycle and allow the dayshift to
reassess or issue a more short-fused/targeted watch.
Rain showers linger tonight into Wednesday particularly
downwind of Lake Erie and over the higher elevations, but for
the most part we anticipate a multi-day drying trend with near
to slightly below normal temps and comfortably low humidity from
midweek into the last weekend of July.
&&
.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
A few areas of low ceilings this morning with some showers
already developing over the Allegheny front. Clouds and
precipitation activity will only increase throughout the day
ahead of an approaching cold front.
Conditions will waffle between MVFR and VFR through the morning
as -SHRA pop up ahead of the main area of precipitation. The
area has been placed in an enhanced risk for severe storms
through the afternoon hours. However, confidence on the exact
time of any storm passing over an individual airport is only
about 20% at this time. Hence VCTS was added for the afternoon
time frame with the expectation that timing will be narrowed
down as we move closer to the event. In any case, plan for +TSRA
to dot the state through the afternoon into evening with the
usual suspects of wind shear, turbulence, heavy rain, and the
potential for hail (especially aloft where it hasn`t had time to
melt on its way down).
In the wake of the storms this afternoon expect low ceilings to
stick around for MVFR to IFR across the entire area leading into
Wednesday.
Outlook...
Wed...Periods of lingering showers possible Wednesday morning as
the frontal boundary exits the state.
Wed afternoon-Sat...Good VFR conditions expected.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
WHAT HAS CHANGED...Lambert/Steinbugl
KEY MESSAGES...Lambert/Steinbugl
DISCUSSION...Lambert/Steinbugl
AVIATION...Lambert/Bowen/Tyburski
NWS CTP Office Area Forecast Discussion
