FXUS61 KCTP 230847
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
447 AM EDT Sun Aug 23 2026

.WHAT HAS CHANGED...
Adjusted POPS up for Central and Southern PA today by about 20 
percent from NBM guidance. 

&&

.KEY MESSAGES...
1) Unseasonably deep upper low over the Upper Great Lakes today
will move Southeast to Lake Ontario by Monday morning bringing
another few rounds of showers and thunderstorms, mainly across
Northern PA this afternoon and evening.

&&

.DISCUSSION...
KEY MESSAGE 1: Unseasonably deep upper low over the Upper Great 
Lakes today will move Southeast to Lake Ontario by Monday 
morning bringing another few rounds of showers and 
thunderstorms, mainly across Northern PA this afternoon and 
evening.

A subtle shortwave trough rotating around the southeast side of
the upper low will spark some afternoon/evening showers and TSRA
today, followed by only a brief downtrend in convection before a  
well-defined trough moves SE with its axis near the PA/OH border
by shortly after midnight tonight. 

HREF and SREF MUCAPEs will top out between 750-1000 j/kg with
wet bulb zero levels descending about 3-4 KFT to only around 6
KFT AGL across the Northern Mtns this afternoon and tonight. 
It's almost a slam dunk to see some periods of significant small
hail from the stronger low-topped TSRA between 18Z Sun and 00Z
Monday across the NW and maybe the Central/Ncent Mtns. SPC has a
marginal risk of SVR TSRA for today across all of the CWA except
for the southern tier layer of counties. Coincidentally, NBM
POPS had to be raised by at least 20 percent (to agree with the
SPC outlook) across the Central and Scent Mtns along with much 
of the Middle and Lower Susq Valley where a relative min of zero
to 10 POPs was noted. 

Luckily, this second and more potent upper trough will be 
pivoting over the Commonwealth overnight tonight with MUCAPE of 
only a few hundred J/KG, supporting mainly showers and perhaps a
low-topped TSRA or two moving inland from the warm waters of 
Lake Erie. 

Maxes only in the 60s and a brisk W wind across the northern and
western mtns will make it feel much more like Sept/Oct than 
mid- Aug. Valley locations will see more sun preceding any
convection with high temps reaching the mid 70s to near 80F in
the Lower Susq Valley.

Similar conditions are expected for Monday with the center of 
the upper low still hanging around our longitude and only moving
slowly poleward. The SHRA/TSRA will likely be confined to only 
the nrn tier of counties in PA on Monday.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
Working both shifts today, so 00Z TAF set done largely already
earlier this aft (18Z set), so main adjustment for the new set
is for timing of showers and storms as of early evening. 

Back edge to most everything is near the PA, OH border.

More information below.

Showers are pivoting east and will only impact MDT and LNS for
another hour or two as of 06Z. Some back end, scattered light 
showers have been noted too which may impact UNV and possibly 
IPT if they hold together. 

The main restrictions tonight look to be in the form of low 
ceilings as high clouds move out of the area. Forecaster 
confidence in exact impacts is on the lower side, particularly 
in relation to what degree low level moisture will affect 
visibility. Regardless, widespread MVFR ceilings leading into 
IFR ceilings overnight looks to be the most likely solution at 
this time. 

As the sun rises, current guidance favors MVFR ceilings 
lingering into mid-morning. Once daytime convection kicks in and
cloud ceilings raise, VFR will be favored through tomorrow. Lake
effect rain bands are possible in the northwest, which may
impact BFD, although exact timing is uncertain. Added PROB30 to
highlight best chance of thunderstorms in the afternoon. 
Cooling temperatures aloft behind the front and a 20+kt 850mb 
jet should allow for gusty westerly winds tomorrow. 

Outlook... 

Mon-Wed...Patchy morning fog, otherwise mainly VFR conditions 
return early next week with lower statewide precipitation
chances.

Thu...Chance of showers and storms again.

&&

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

&&

$$

WHAT HAS CHANGED...Lambert/Dangelo
KEY MESSAGES...Lambert/Dangelo
DISCUSSION...Lambert/Dangelo
AVIATION...Lambrech