NWS Forecast Discussion

FXUS61 KCTP 250237

Area Forecast Discussion
National Weather Service State College PA
1037 PM EDT Wed Jul 24 2024

* A cold front will initiate scattered showers and storms on
  Thursday afternoon and evening, mainly in southern PA.
* High pressure in the wake of the cold front will bring
  abundant sunshine, slightly lower humidity, and seasonably
  warm temperatures.
* Excessive heat risk ramps up again by the middle of next week.


Still a few storms hanging on across eastern PA this evening as
sufficient shear combines with waning instability to produce
occasional gusts of 40-50mph. Convection will wane by midnight
with partly cloudy skies remaining overhead tonight. A cold
front will begin to move across northwest PA by daybreak and
will usher in lower humidity and clearing skies behind it into
the day on Thursday.

Best signal for clearing skies and light winds overnight is
across western PA and have included some patchy valley fog in
the forecast for parts of Warren and McKean County to reflect
this possibility. Patchy fog will also be possible in locations
that received rainfall today, but think there will be enough
clouds overhead to preclude widespread fog development across
most of the forecast area.

Lows by daybreak should range from the upper 50s over the
northern mountains, to near 70 in the Lower Susquehanna Valley.


On Thursday, the cold front will slowly make its way across the
Commonwealth, reaching the far southeastern counties by late
afternoon/early evening. Showers and thunderstorms should bubble
up along the front again during the afternoon, coincident with
peak heating. Stability/shear profiles again support a marginal
risk for isolated instances of strong winds and hail over the
Lower Susquehanna Valley. Although muggy conditions are likely
to persist on Thursday, we will see some drier air/lower
surface dew points sneak into northwestern PA by late afternoon.
The risk for flooding should be negligible as a result of recent
dryness and meager PWATs on the order of 1 inch.

By Thursday night, surface ridging from the northwest will bring
a quick end to the convection and the influx of much drier air.
Fog again looks like a good possibility across northwest PA
closest to the ridge axis. Overnight lows into Friday morning
will be refreshingly cool - perhaps dipping into the upper 40s
in northwest PA and dropping into the 50s for most of the rest
of the forecast area.

Ridging remains in place Friday and Saturday with stellar
summer weather on tap. Mainly clear skies, seasonably warm
temperatures, and considerably lower humidity levels than what
we`ve experienced lately will be welcomed. The only hindrance
for this weekends weather will be the likely return of wildfire
smoke from Canada. Most of the smoke should remain aloft with no
expectation of dangerous near-surface concentrations, but hazy
skies and colorful sunrises/sunsets appear likely through the
weekend (and as long as our upper level flow has its origins in


Surface high pressure will remain in control through the
weekend, but upper level ridging will build on Sunday, resulting
in a trend toward warmer conditions and highs back in the low to
mid 90s across the southern tier. More humid conditions will
also return by early next week, as the surface high slips off
of the East Coast and a return southwesterly flow develops.

Guidance suggests a cutoff upper low may develop within the
western Atlantic ridging at the beginning of next week,
resulting in a slower more blocky pattern. The next chance of
showers/storms begins late Monday across western PA, with the
chance then increasing into Tue and Wed across central PA as
upper shortwave troughs slowly move through the region.

There remains some uncertainty with how the upper level pattern
will progress next week, but building high pressure over the
western and central US will bring an increasing threat for
excessive heat as the calendar flips from July to August.


A broken line of showers and thunderstorms extends from UNV to
IPT as of 00Z and will capable of producing strong wind gusts
and brief restrictions as it continues to move eastward. Shower
activity should diminish overnight. High res guidance suggests
a good chc of low clouds (borderline IFR/MVFR) developing over
the western highlands overnight (both BFD and JST have a 70-80%
chc of seeing IFR cigs). There remains some questions in regard
to how far east the low clouds extend, but there is at least
some chance that MVFR ceilings make it all the way to UNV and

Any low clouds should diminish Thu AM, with a renewed chc of
showers/storms by afternoon as a cold front crosses the region.


Fri...Improving conditions.

Sat-Mon...Dry weather with predominantly VFR conds expected.


The average temperature from July 1 to July 23, 2024 at
Harrisburg was 80.8F, which is tied for the 3rd warmest Jul
1-23 period on record (81.9F in 2020, 81.2F in 1999, 80.8 in
2019 and 1955).

The average temperature from June 1 to July 23, 2024 at
Harrisburg was 78.1F, which is the warmest meteorological
summer- to-date on record.

The average temperature from January 1 to July 22, 2024 at
Harrisburg was 56.0F, which is the warmest year-to-date on





NEAR TERM...Banghoff
SHORT TERM...Jurewicz/Banghoff
LONG TERM...Fitzgerald/Colbert

NWS CTP Office Area Forecast Discussion