695
FXUS61 KCTP 160327
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1127 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 at least Thursday
* Heat risk builds Wednesday and likely peaks on Thursday with
  potential for heat index value to exceed 100 degrees in south
  central PA

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
With stray evening showers all but dissipated, mainly clear
skies tonight will set the stage for areas of fog/stratus
developing into early Wednesday morning. It will be muggy with
min temps 65-75F or 5 to 10 degrees above climo.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Fog/low stratus will mix out shortly after sunrise giving way
to a mix of sun and clouds into the late morning Wed. Key
message centers around an elevated risk of flash flooding due to
multiple rounds of heavy shower/tstm clusters Wed afternoon
into Wed night.

Given impressive thermodynamics (MUCAPE 1500-3000 J/kg),
99th+ percentile PW (1.5-2.2") and midlevel vorticity associated
with an MCV, localized rainfall rates of 2"/hr are probable in
convection Wed afternoon and evening. Repeat rounds of heavy
rain/storms could quickly produce point totals of 2-4" in some
areas. This may result in instances of flash flooding,
particularly if the heavy rain falls in basins that picked up
heavy rainfall earlier this week. On a positive note, latest
HREF guidance keeps the heaviest rain west of those areas
hardest hit on Monday, but we will continue to monitor for
trends east. Another positive note is that the CAMs have most
convection firing along NW-SE oriented boundaries, then
advecting towards the northeast with the flow. This would tend
to favor multiple rounds of convection rather than true
training. Although a flood watch has not been issued, we will
continue to consider it into the day Wednesday if the signal for
flash flooding does trend higher.

While vertical shear will remain limited, SPC did expand the
MRGL risk over central PA to account for potential isolated
strong wind gusts in water loaded downdrafts 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. Rain is likely to return to the forecast
Sunday, with at least chance PoPs continuing through Tuesday with
scattered thunderstorms. Typical max temps near the historical
avg for mid to late July with nighttime lows a few deg abv
climo.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
The rest of this evening should remain mostly quiet. There are a
few rain showers lingering across the state, but these showers
are mostly stationary and the probability of any restrictions
due to them remains less than 30 percent. Skies overnight will
remain mostly clear to scattered high clouds in some spots.
Winds tonight will remain calm with recent model soundings
showing little to no winds in the lowest 1km. Given the moist
atmosphere and calm winds fog is expected to impact most
airfields overnight tonight. Any fog that does develop will be
patchy in nature and quickly lift around sunrise.

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.
Multiple rounds of showers and thunderstorms are expected across
the region by Wednesday afternoon and evening. The timing of
these storms will be difficult to nail down given the nature of
the surface convergence that will be driving them, but most
airfields will see periods of thunderstorms Wednesday afternoon.
These storms may linger into at least early Thursday morning,
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/Colbert
SHORT TERM...Steinbugl/Colbert
LONG TERM...Jurewicz/Steinbugl/Colbert
AVIATION...Bowen