467
FXUS61 KCTP 151104
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
704 AM EDT Wed Jul 15 2026

.WHAT HAS CHANGED...
* Lowered dewpoints this afternoon to account for mixing down of
  dry air aloft
* Mentioned risk of smoke from Ontario and northern Minnesota
  reducing air quality beginning tonight and sticking around
  through the end of the week.

&&

.KEY MESSAGES...
1) Hot temperatures and modest humidity will increase the risk
of heat impacts this afternoon.

2) Smoke from Ontario and northern Minnesota may reduce air
quality beginning tonight and sticking around through the end of
the week.

3) An unsettled weekend with rain and storms will kick off a
cooling trend into next week.

&&

.DISCUSSION...
KEY MESSAGE 1: Hot temperatures and modest humidity will
increase the risk of heat impacts this afternoon.

No change to heat headlines this afternoon. Max heat index
peaks in the 100-104 range this afternoon for locations east of
I-99 and along/south of I-80. Boundary layer mixing and
noticeable WNW breeze favored lowering dewpoints a couple
degrees this afternoon. Whereas the heat wave over Fourth of
July had dewpoints in the middle 70s, dewpoints this afternoon
will likely mix out into the mid 60s. It will certainly feel
hot/humid, but not nearly as oppressive as a couple weeks ago.

A weak cold front dropping down from the north through the day
today will knock dewpoints down further, especially across the
northern tier. This front may also initiate a few widely
scattered thunderstorms, highest chance over eastern zones (SPC
D1 SWO MRGL risk focused over eastern PA clips Schuylkill and
Lebanon Co). Dry air and any reduction to insolation via
wildfire smoke will be limiting factors for convection. But
sufficient bulk shear (40-50+ kts) will be more than sufficient
for a few severe downbursts IF any storms develop. Most likely
timing for storms will be 4PM to 9PM.

KEY MESSAGE 2: Smoke from Ontario and northern Minnesota may reduce air
quality beginning tonight and sticking around through the end of
the week.

HRRR-Smoke guidance suggests smoke from upstream wildfires in
in Ontario and northern Minnesota may reduce air quality across
much of Pennsylvania beginning tonight. The model shows sfc
level smoke concentrations rising sharply behind the cold front
this evening, and continuing to climb through the overnight
into Thursday morning. Widespread smoke is then forecast to
stick around through at least Friday with no real airmass change
in sight. In addition to air quality impacts, marginal
visibility restrictions will be possible where sfc smoke
concentrations are highest. The smoke may also make for a bright
red sunset/sunrise each night/morning through Saturday morning.
Historically, smoke also has an appreciable impact on afternoon
high temperatures, so we shaved a couple degrees off of expected
highs both Thursday and Friday.

At this time, the PA Department of Environmental Protection does
not have plans to issue any Air Quality Alerts as they don`t
anticipate critical 24-hour average particulate concentration
thresholds to be reached, but they will continue to monitor
smoke concentrations over the next couple days. This event
should not reach the dangerous smoke levels of June 2023, but
you can expect to smell smoke and experience a noticeable
reduction in visibility over the next couple days.

KEY MESSAGE 3: An unsettled weekend with rain and storms will kick off a
cooling trend into next week.

By Friday night, upper level ridging will begin to break down
and transition to an upper trough by early next week. As this
happens, multiple rounds of showers and thunderstorms are likely
across PA in a northwesterly flow regime. Widespread showers and
storms are expected this weekend, though some uncertainty
remains with the exact timing and intensity of storms. SPC still
has not highlighted any areas of severe weather this weekend,
but future upgrades are possible (likely?) as confidence
increases in the exact corridors of stronger storms.

On the whole, the combination of upper troughing and stormy
weather will lead to a decreasing temperature trend into next
week. Ensemble guidance continues to latch onto the possibility
of considerably cooler conditions by the middle of next week in
the wake of a cold front. It is possible that some locations
could see low temperatures in the 40s and 50s on a couple
mornings. After this stretch of warmth, such a pattern shift in
late July would be a welcome sight.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
Prevailing VFR is expected through the daytime Wednesday as
high clouds and wildfire smoke aloft pass overhead. Beginning
around 00Z Thursday, concerns grow for visibility restrictions
due to near-surface smoke moving in from Ontario & northern
Minnesota

Cannot rule out an isolated SHRA/TSRA this afternoon, with the
highest probability (~15%) being across east-central PA.
Otherwise, we will see more of the same with hot and humid
conditions and some wildfire smoke aloft producing hazy skies.

After 00Z Thursday, visibility restrictions due to near-surface
smoke from Ontario/Minnesota become more likely. A blend of the
HRRR/RRFS smoke products were used to determine smoke
placement, with visibilities in the TAF kept at 6SM for now
given uncertainty regarding how those wildfires will evolve
today + what the downstream implications will be. Based on the
HRRR/RRFS guidance, visibilities may drop to 2-4SM in areas
where the smoke is most dense, with somewhat higher confidence
in smoke at KBFD/KIPT Wednesday night (potentially
KUNV/KMDT/KLNS as well, with lower confidence). The smoke plume
is currently forecast to overspread the Commonwealth as
Thursday progresses, with reduced visibilities likely (mainly
3-6SM).


Outlook...

Thu-Fri AM...Mainly VFR, with areas of late night/AM fog. Some
reduced visibility possible from smoke, with an isolated late-
day SHRA/TSRA possible.

Fri PM-Sun...Chance of showers and t-storms, mainly during
the afternoon and early evening hours on Saturday and Sunday.

&&

.CLIMATE...
Daily record high max temperatures for July 15th
_______________________
SITE    | RECORD/YEAR |
-----------------------
MDT     |   99/2024   |
-----------------------
IPT     |  103/1995   |
-----------------------
AOO     |   98/1995   |
-----------------------
BFD     |   88/2013   |
-----------------------
STCP1   |   97/1887   |
-----------------------

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT this evening for PAZ019-026>028-
045-046-049>053-056>059.
Heat Advisory from 11 AM this morning to 8 PM EDT this evening
for PAZ035-036-063>066.

&&

$$

WHAT HAS CHANGED...Banghoff
KEY MESSAGES...Banghoff
DISCUSSION...Banghoff
AVIATION...Teare/Evanego
CLIMATE...Steinbugl