FXUS61 KCTP 220842
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
442 AM EDT Sat Aug 22 2026

.WHAT HAS CHANGED...
SPC expanded the MRGL RIsk for SVR TSRA areas today (Western
half of the CWA) and for tomorrow (approx 90 percent of the
CWA, except for the Southern Tier of the state). 

&&

.KEY MESSAGES...
1) Upper level low pressure swinging SE from the upper Glakes
to southern Ontario will lead to high temps trending cooler by 
a few to several degrees each day through Monday along with 
periods of showers and isolated to scattered gusty 
thunderstorms. 

&&

.DISCUSSION...
KEY MESSAGE 1: Upper level low pressure swinging SE from the 
upper Glakes to southern Ontario will lead to high temps 
trending cooler by a few to several degrees each day through 
Monday along with periods of showers and isolated to scattered 
gusty thunderstorms. 

Significant amplification of a longwave trough will occur over
the next several days across the Glakes, Mid Atlantic region  
and Central Appalachian with 500 mb height falls of 60-100
meters and mean 850-700 mb layer temps of around 6 deg C from
this evening to Monday morning. 

Abundant sunshine expected across the CWA North and West of the
Lower Susq Valley with max temps this afternoon generally
between 75-80F. 

The initial lead shortwave and right entrance region of a 65 kt
upper level jet trailing a zone of very sharp upper diffluence
over the western 1/3 of PA late today/early tonight will 
support development of scattered strong to severe TSRA across
the western 1/3 to 1/2 of our CWA with the likely
evolution/upscale growth of multicell clusters into a bkn line 
of TSRA with its axis near the RT 219 corridor between 00Z and 
03Z Sunday where 0-1KM EHI will be in the 1-1.5 M2/S2 range and 
0-3 KM Bulk shear will be average 20-25 KTS with some pockets 
just above 30 kts across the NW Mtns near KBFD at 03Z Sunday. 

HREF MU CAPE Values do drop off fairly quickly from their late 
afternoon/early evening peak of 1200-1500 J/KG across western 
PA, and the severe threat will be diminished by 02z across the 
Mtns of Western PA. The eastern half of PA will get the 
gradually weakening convection later this evening/overnight.

For Sunday, the best larger scale/deep layer cooling aloft will
occur across the eastern half of the state and that will be the
focus for the SVR threat. MU CAPE will be lower by around 500
J/KG but deep layer swrly shear will be 35-40 kts across our
eastern CWA. Therefore, SPC's MRGL risk covers the better threat
for gusty winds with the storms across the eastern half of PA on
Sunday with some isolated occurrences of pea to marble size hail
in the taller storms Sunday. 

The cyclonic flow may keep showers downwind of Lake Erie into 
Monday. Daytime highs will be near to slightly below the 
historical average for late August, making it feel more like mid
September especially Sunday into Monday. SPC trimmed the MRGL 
back a bit to the west on Saturday, which should feature early 
day clouds and a few showers spreading from SE to NW during the 
day. Drier/less humid conditions are likely to prevail during 
the first half of next week.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
As mentioned in the previous update, drier air and slightly more
persistent winds will preclude a more widespread fog risk
tonight. BR development at some sites though cannot be ruled
out though. Confidence in MVFR ceilings developing this morning
is highest at LNS and to a lesser extent MDT given greater
moisture return in the southeast.

While VFR in a SCT/BKN low level cloud deck will be the
prevailing conditions tomorrow, some isolated showers are
possible in the afternoon. Chances for this are highest at MDT
and LNS with spotty morning activity possible as well. This
activity may leadto bounces between VFR and MVFR throughout 
the day tomorrow in the southeast, with greater restrictions
more likely at LNS. 

This showery activity will be ahead of a cluster of storms
moving through in the evening/early night. Have updated PROB30s
for -TSRA to reflect most confident timing at the current
moment. HREF ensemble and NBM trending later in storm timing in
their most recent runs. Should a strong core cross paths with an
airfield, brief IFR restrictions are possible.  


Outlook... 

Sun...Restrictions possible, mainly NW in SHRA. Improvement 
elsewhere. 

Mon-Wed...Patchy morning fog, otherwise mainly VFR conditions 
return early next week.

&&

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

&&

$$

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