675
FXUS61 KCTP 111027
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
627 AM EDT Thu Jun 11 2026

.WHAT HAS CHANGED...
Heat Advisory issued for Lancaster, York, Adams, Cumberland,
Dauphin, and Lebanon Counties for Thursday and Friday.

&&

.KEY MESSAGES...
1) Increasing heat and humidity will bring increased risk for
heat-related illnesses Thursday, and especially on Friday.

2) Daily shower and thunderstorm chances continue through the
end of the work week. Some strong to severe thunder with
damaging winds possible.

3) A refreshing decrease in humidity is a good bet this weekend
with high pressure moving in after a cold front.

&&

.DISCUSSION...
KEY MESSAGE 1: Increasing heat and humidity will bring
increased risk for heat-related illnesses Thursday, and
especially on Friday.

Portions of Central PA may wake up to patchy fog this morning
thanks to a very humid airmass and overnight showers/storms. With
an upper level ridge in place advecting in a very warm to hot
airmass, heat and humidity will continue to build today and
Friday, particularly for the eastern two thirds of the forecast
area.

There is quite a bit of uncertainty remaining in how high the
temperatures and heat index values get due to variable cloud
cover and the potential for showers and thunderstorms both days
(especially Friday). The continued thinking is that the NBM is a
bit too high with both temperatures and dew points both days,
especially given the recent high bias. Therefore, similar to
previous forecast cycles, went a few degrees cooler than the
NBM.

All of this being said, the forecast heat index for Thursday
and Friday still get to the upper 90s and low 100s for the
southeastern portions of the area on Thursday, particularly the
Harrisburg/Lancaster/York areas. Heat Advisories have been
issued for Lancaster, York, Adams, Cumberland, Dauphin, and
Lebanon Counties for Thursday and Friday where HREF
probabilities of heat index > 100F are highest.

   ---------------------------------------------------

KEY MESSAGE 2: Daily shower and thunderstorm chances continue
through the end of the work week. Some strong to severe thunder
with damaging winds possible.

Underneath a broad ridge of high pressure, a couple shortwaves
will drift across Pennsylvania over the next few days.
Sufficient instability in the presence of warm & moist air along
with weak but sufficient shear will lead to multiple rounds of
showers and thunderstorms today and tomorrow. This will be a
typical summerlike pattern with many storms on radar and
lingering questions about how strong they`ll get. If multicell
clusters can develop large enough cold pools, an elevated threat
of damaging wind gusts may materialize in the form of an MCS.
Such a scenario cloud produce a swath of more significant wind
damage (most likely on Thursday). Slight Risks with 30% wind
probabilities have been issued for both today and Friday across
southeast PA.

A cold frontal passage will occur on Friday. An approaching upper
trough and high available moisture suggest severe thunderstorms
are possible. But, the small ridge that pumps up overhead late
Thu could be a setback for how widespread the threat will be.
The biggest question is timing/speed of the cold front. A faster
progression could mean the cold front clears our area before
peak heating (lower threat of damaging winds), while a later
arrival could spell more concern for severe weather.

It is worth noting that recent hi-res convective
allowing models actually bring most of the convection to NW PA
today and fail to initiate many storms at all in our forecast
area on Friday. Possible flies in the ointment to monitor.

The repeated shots of scattered to numerous SHRA/TSRA over the
next 2 days is likely to yield lower FFG thresholds and some
flash flooding would become possible, too. But, it has been very
dry recently, and everything is growing and thirsty, ready to
soak up as much as it can. As always, too much of a good thing
can be bad. We`ll keep an eye on the soil saturation and other
factors that could lead to flooding.

      ---------------------------------------------------

KEY MESSAGE 3: A refreshing decrease in humidity is a good bet
this weekend with high pressure moving in after a cold front.

Following the passage of the aforementioned cold front, much
more comfortable conditions will arrive on Saturday and Sunday.
Temperatures will remain warm (highs in the 80s and even some
lower 90s on Sunday), but dew points will be much lower (in the
50s and lower 60s, instead of the 70s). Then, cooler
temperatures arrive by Monday with highs in the 70s to lower
80s. This will be due to another cold front passage on Sunday,
which will bring a renewed chance for showers and
thunderstorms.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
Ceiling/visibility restrictions from overnight mist & fog will
trend to VFR regionwide through diurnal boundary layer mixing.
While the primary convective threat will be later today, stray
thundershowers developing within a moist (PWATs > 1.5") and
destabilizing (MUCIN trending to 0 J/kg) environment may yield
brief visibility restrictions & gusty winds.

Additional rounds of convection are expected Thursday
afternoon/evening as another, more focused shortwave crosses the
moist/unstable environment in place. Multicell clusters &
quasi-linear segments are favored given marginally favorable
deep layer shear (20-25 kts), along with threat for gusty to
perhaps severe-level winds given steep low-level lapse rates
(8-9 C/km) and moderate-high DCAPE (1000-1250 J/kg). Visibility
restrictions will be likely in these storms, especially given
high moisture content (PWATs around 1.5") which will bring heavy
rain in storms. Convective activity across central PA will
downtrend after 00Z as the shortwave progresses east of our
area, with patchy fog possible once again Thursday night given
moist environment & breaks in cloud cover.

Outlook...

Thursday afternoon...Restrictions possible in scattered
-SHRA/-TSRA.

Friday...Restrictions expected as FROPA brings line of -TSRA.

Saturday...Mainly VFR.

Sunday...VFR favored early, with restrictions possible as FROPA
brings chance of -SHRA/-TSRA later in the day.

Monday...Additional scattered -SHRA and associated restrictions
possible.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM this morning to 8 PM EDT Friday for
PAZ057-059-063>066.

&&

$$

WHAT HAS CHANGED...Banghoff/Colbert
KEY MESSAGES...Banghoff/Colbert
DISCUSSION...Banghoff/Colbert
AVIATION...Teare