316
FXUS61 KCTP 112306
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
706 PM EDT Thu Jun 11 2026

.WHAT HAS CHANGED...
Heat Advisory remains in effect across Lancaster, York, Adams,
Cumberland, Dauphin, and Lebanon Counties for the rest of today
and Friday.

&&

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

2)  Shower and thunderstorm chances continue through
the rest of today and again Friday. Some severe thunderstorms
will occur and produce damaging wind gusts.

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.

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 amounts
of alto cu from weak warm advection aloft and remnant cloud
cover from overnight/mid morning convection. Increasing chc
for late afternoon and evening SHRA/TSRA will also add to the
uncertainty of max temps.

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: Shower and thunderstorm probabilities will ramp
up across the NW 1/3 to 1/2 of the CWA through 00Z Friday, with
the target time across the Middle and Lower Susq Valley
occurring between 22Z Friday and 01Z Sat. Another few round of
TSRA are expected Friday. Some severe thunderstorms will occur
and produce damaging wind gusts.

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 Friday.

The first feature at the surface and aloft that will help to
support and increase the coverage of TSRA will come in the
form of a compact shortwave trough centered over Central Lake
Erie with its trough axis extending south across Western PA and
Eastern Ohio. Movement of this features and its many showers and
TSRA is to the ENE at just over 30KT.

Multiple storm clusters/line segments have there axis nearly
perpendicular with the moderate, 20-30 kt 0-3KM bulk shear
vector, so training and very heavy rain is not likely at this
point.

Meso-B lift and 1-2 deg C of cooling within the mid levels
(~700 mb), along with westerly 0-3 km bulk shear increasing to
around 30 KT will help to increase instability and organized
updrafts in TSRA that should push through much of our CWA in 2-3
quasi-linear features, with the main severe wx threat coming in
the form of localized wind damage associated with mini
bows/broken-S signatures.

If these 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 across the Mid/lower
Susq Valley late this afternoon/evening and potentially in any
part of the CWA on Friday. 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 /00Z FRIDAY THROUGH TUESDAY/...
Band of showers and storms moving along at a decent clip.
Main area to see more showers and storms until mid to late
evening will be MDT and LNS.

Lower clouds and fog will likely form overnight, mainly
in areas that had rain today.

Expect winds to pick up Friday morning, with conditions
expected to become VFR again by late morning or early aft.

Have some VCSH in most of the TAFS later Friday, NAM model
not showing much potential with showers and storms. Did not
have VCSh in BFD, as even less chc there. Later shifts can
adjust more on Friday as needed.

A break on Saturday, but a stronger cold front on Sunday
will bring the potential for more strong storms on Sunday.

Outlook...

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.

Tuesday...Still a slight chance of showers and storms.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT Friday for PAZ057-059-063>066.

&&

$$

WHAT HAS CHANGED...Lambert/Banghoff/Colbert
KEY MESSAGES...Lambert/Banghoff/Colbert
DISCUSSION...Lambert/Banghoff/Colbert
AVIATION...Martin