179
FXUS61 KCTP 070929
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
529 AM EDT Mon Jul 7 2025

.SYNOPSIS...
* Hot and Humid today with thunderstorm downpours concentrated
  in the northwest Alleghenies and near the I-95 corridor
* Scattered T-storms will be focused primarily over the
  southeastern half of the Commonwealth Tuesday afternoon
* Seasonably warm and muggy for the rest of the week with
  scattered thunderstorms during the afternoon and evening

&&

.NEAR TERM /THROUGH TONIGHT/...
A moist southeast flow ahead of the circulation associated with
the remnants of Chantal will bring low clouds/ridgetop fog and
perhaps an isolated rain shower to south central PA early this
morning. The increasing cloud cover and low level moisture will
make for a very warm/muggy start to the day with sunrise temps
65-75F.

Early cloud cover should peel off the east northeast with partly
to mostly sunny skies across the majority of central PA to start
the afternoon; the exception will be the far southeast zones.
Today will be hot and humid with max temps in the mid 80s to low
90s or 5-10F above the historical average for early July. Max
HX values approach 100 in many of the central and eastern
valleys.

There are two areas to focus on today based on hires ensemble
guidance and severe t-storm/excessive rainfall outlooks from SPC
and WPC:

1. Northwest Alleghenies: Widely scattered thunderstorms are
expected to develop this afternoon along/ahead of a slow-moving
cold front pushing southeastward from the Lower Great Lakes.
Around 30 kt of effective shear amid a diurnally destabilizing
boundary layer will allow for loosely organized multicell
clusters capable of producing isolated wind damage (svr tstm
risk level 1 out of 5 or MRGL). HREF 3hr QPF PMM signal also
highlights a locally heavy rain threat across this area (peaking
18-21Z downwind of Lake Erie) with >1.5" pwats supporting some
isolated point amounts of 2+ inches possible.

2. The far eastern portion of the Lower Susquehanna Valley:
Isolated flash flood concerns will extend along the I95 corridor
as tropical moisture associated with the remnants of Chantal
track from southern VA over the DelMarVA into southern NJ by 00Z
Tue. PWATs >2 inches and well defined mid level vort max will
drive potential for locally heavy to excessive rainfall which
appears to align with a convergence axis over southeast PA.
Although higher probs for heavy rain are positioned just to the
east of the Lower Susq Valley in the PHI/LWX CWAs (I-95), it is
close enough to monitor for a possible short-fused FF watch.

Coverage of showers fades overnight with a good signal for post
frontal low clouds over the western mtns and areas of fog across
the central and eastern valleys. Another warm and muggy night in
most locations with low temps in the 65-75F range.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Max temps drop 5-10 degrees behind the front over the western
1/2 of the CWA on Tuesday. The latest guidance shows the front
stalling out or becoming quasi stationary over CPA by 00Z Wed.
There will be marginal risk of severe storms and excessive
rainfall mainly for areas to the southeast of the frontal zone
where there will be plenty of MLCAPE and 70+ dewpoints. Tall or
thin profiles suggest more of a +RA vs. severe storm threat, but
a few stronger multicellular cores may be capable of producing
an isolated damaging wind gust.

There also remains some concern for max HX values to reach or
exceed the century mark in the LSV Tuesday afternoon. A heat
advy may be needed; for now we coordinated with PHI to not
include any of the Lehigh/Lower Susq zones but will continue to
highlight in the HWO.

Best odds for a thunderstorm on Wednesday remains along the MD
line where the best moisture/instability overlay will exist. At
this time, t-storms are expected to be non-severe with heavy
rain risk shifting to the south of the Mason Dixon line. Max/min
temps remain seasonably warm for early/mid July.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
PoPs rise again Thursday with the approach of another shortwave
trough. The forecast for Friday and the weekend is more
uncertain, with some guidance suggesting a break in the
unsettled pattern, and others suggesting active weather
continues. An active pattern would favor continue heat/humidity
while a quieter pattern could support the intrusion of lower
dewpoints and more refreshing conditions.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
Low level moisture drifting north across the Mid Atlantic
Piedmont (ahead of the remnants of TS Chantal) and PWAT values
exceeding 2 inches almost all the way north and west to the I-81
corridor will lead to BKN-OVC stratus into the late monring
hours before warmest surface temps and vertical mixing raises
the bases to above 030.

A few showers may affect MDT/LNS during the mid to late morning
hours as tropical moisture moves into the air space. Afterward,
scattered showers and storms will move across NW PA this
afternoon and briefly into Central PA late today/early this
evening ahead of a slow moving cold front.

Will keep the prevailing conditions VFR with the mid afternoon
through evening hours bringing a few brief periods of MVFR CIGS
and VSBYS in the heavier showers and storms.

Patchy fog is possible at all TAF sites late tonight and Tuesday
morning. However, cloud cover and a lite breeze from the west
later tonight will likely negate a significant threat for
widespread fog.


Outlook...

Tue...Restrictions in MVFR cloud (northwest) and scattered
showers/storms (southeast).

Wed...Best chance for storms and restrictions in southern PA.

Thu-Fri...Potential for showers and thunderstorms, mainly
aftn/eve.

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Lambert/Banghoff
AVIATION...Lambert/Gartner