673
FXUS61 KCTP 151927
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
327 PM EDT Tue Jul 15 2025

.SYNOPSIS...
* Elevated risk of excessive rainfall and flash flooding
  Wednesday afternoon and evening
* Scattered thunderstorms with locally heavy rain forecast
  through late week
* Heat risk builds Wednesday and likely peaks on Thursday with
  potential for heat indices to exceed 100 degrees

&&

.NEAR TERM /THROUGH TONIGHT/...
Very isolated and weakly forced airmass/terrain induced
convection mainly over the Allegheny "rim" this afternoon
should quickly dissipate this evening with the loss of daytime
heating.

Crumbling cumulus gives way to mainly clear skies tonight with
areas of fog/stratus are set to redevelop into early Wednesday
morning. It will be muggy with min temps 65-75F or 5 to 10
degrees above climo.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Fog/low stratus mix out shortly after sunrise giving way to a
mix of sun and clouds into the afternoon. Key message for
tomorrow centers around an elevated risk of excessive rainfall
and potential for flash flooding.

Return flow pattern continues to set the stage for rounds of
enhanced thunderstorms capable of producing very heavy rainfall
on Wednesday afternoon and evening. Given impressive
thermodynamics (MUCAPE >2000 J/kg), exceptional to near daily
record moisture availability (PW 1.5-2.2") and strong llvl
convergence signal, localized rainfall rates of 2"/hr are
probable and could quickly produce point totals of 2-4" in some
areas during the afternoon and evening. This will likely result
in instances of flash flooding particularly in areas recently
inundated by heavy rain over the past 24 to 48hrs. A watch will
likely be needed in the next 1-2 forecast cycles with growing
confidence based on recent trends in the hires/CAM guidance. The
heavy rain threat should taper off into Wednesday night.

While vertical shear will remain quite limited, SPC did expand
the MRGL risk over central PA to account for potential isolated
strong water-loaded wind gusts that could occur in the most
intense storm cores.

Building heat and increasing dewpoints are expected through
midweek with a peak in Heatrisk on Thursday afternoon. A heat
advisory may be needed for portions of south central and
southeast PA including the mid and lower Susquehanna Valley.

Additional PM thunderstorms with the potential for heavy
rainfall are likely on Thursday as a cold front pushes to the
southeast from the Lower Great Lakes. Minimum QPF signal over
the southeast half of the CWA may be related to capping and warm
temps aloft that would limit convective initiation/coverage.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Signal in the latest suite of model guidance suggests that we
could be in for a bit of a drier and less humid stretch of wx
heading through the end of the week/start to the weekend. Sfc
cold front stalls just south of the MD line Saturday then
returns back to the north as a warm front by Sunday. So on
balance, Friday and Saturday could be dry in most places for the
majority of the time. Unsettled conditions are likely into
early next week with scattered thunderstorms. Typical max/min
temps near the historical avg for mid to late July with the
largest departures from climo normals vs. nighttime lows.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
For the 18Z TAF group, added VCSH for most of the area, as
clearing skies have quickly resulted in TCU just to the south
of the office here. Also showers near JST on the radar since
late morning.

After Midnight, expect some fog overnight, even without the
rain. This based on guidance and that winds will be light and
dewpoints still quite high.

For Wednesday, a weak upper level trough in combination of
high dewpoints and heating will result in the increasing
chance of shower and storms across the area after late morning.

The activity may linger into at least late Thursday, until a
weak cold front drops south and east of the area.

Outlook...

Thu...Sct/Nmrs SHRA/TSRA.

Fri-Sat...Mainly dry.

Sun...Showers and storms likely.

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Jurewicz/Steinbugl
AVIATION...Martin