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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 230929

Area Forecast Discussion
National Weather Service State College PA
529 AM EDT Thu May 23 2019

Low pressure lifting northeast across the Great Lakes today 
will drag a relatively strong cold front across Pennsylvania 
late This afternoon and evening. 

Cooler and dry weather will follow for Friday. The holiday 
weekend will bring warmer temperatures, higher humidity and a 
renewed chance for showers and storms at times. Memorial Day 
itself looks to offer us with fantastic weather for much of the
day with near normal temperatures and comfortably lower 


The nose of a west-southwesterly LLJ and a belt of enhanced llvl
theta-e convergence was helping to fire off numerous showers and
a few TSRA over the Central Mtns, Mid Susq Valley and Poconos
early this morning. We'll see a several hour lull in the
convection for the late morning (and perhaps into the early 
afternoon near and to the east of the Susq Valley), before the 
convection grows tall enough through the deep strong shear to 
produce scattered to numerous fast- moving severe TSRA posing 
several threats such as FQT Lightning, isolated large hail, 
straight line wind gusts, and even a few tornadoes. 

Strong 0-6km shear is supportive of supercells and the 
combination of low LCL and high 0-1km shear is indicative of a 
tornado threat, especially in the vicinity of surface warm front
over the eastern part of the forecast area.

0-1km Storm Rel Helicity will increase to 200-250 m2/s2 east of
the anticipated lee trough/warm front that will be sliding east
across the Susq Valley during the mid to late afternoon hours.
Across central and western sections of the CWA, hodographs
appear to be more straight-line, and indicative of an enhanced
threat for mini-bow or spearhead echoes with swaths of wind
damage from localized 60-75 mph westerly wind gusts within the
wet microbursts. 

The main source of doubt as to the extent and severity of the
TSRA centers around the amount of ML Cape that can be generated
to overcome the shear and potentially extensive cirrostratus
blow-off from the linear MCS that's racing through Indiana 
ATTM. This MCS will weaken substantially as it moves across the 
NW half of the CWA between about 1430-17Z. Afterward, the 
distribution of sfc boundaries and areas of insolation through 
the aforementioned high cloud layer will dictate when and where 
the strongest convection will fire/become focused. 

Afternoon high temps will be 6-7F above normal or in the mid 
70s north and lower to mid 80s in the southern valleys.

The potentially widespread severe weather event will wind down 
fairly quickly this evening, but storms could linger into the 
late evening near and just in advance of a sfc cold front that 
will sink into southern PA by 02-03Z. This second round of
convection associated with the cold front could be more of a
hail/minor flooding threat this evening across the southern half
of PA.

In the wake of the Cold Front, a pleasant late night tonight, and
Friday is in store for the region with near to slightly above 
normal high temps (mid to upper 60s north and mid to upper 70s 
south), low humidity, and a gusty NW wind of 20-25 mph from the
late morning through Friday afternoon. 


The fast, quasi zonal flow and tap of deep moisture/high PWAT
air stretching from the southern Plains to the Ohio Valley and
Great Lakes will support a few bouts of convection (with 
locally moderate amounts of rain) pushing east across the 
Commonwealth over the holiday weekend. 

Memorial Day appears to be trending drier with a decent amount
of sunshine, a light northwest breeze and low humidity. 

Temperatures for the most part will be warmer than normal, but 
not that abnormal for the first big holiday weekend of the warm 


Scattered showers and isolated thunderstorms continue to move
through the northern half of the state overnight. Have VCTS in
UNV and IPT due to storms just inside the outer range ring of
these airports. Widespread VFR can be expected overnight though
brief restrictions are possible with the dying area of showers 
and thunderstorms that are traversing the region through 09Z.  

Enhanced weather impacts expected on Thursday from mid- 
afternoon through the evening hours as strong to severe 
thunderstorms impact the region. 


Thu...VFR into the afternoon, then strong thunderstorms 
developing mid-afternoon lasting into Thu night.

Fri...Ceiling restrictions poss NW early, then mainly VFR.

Sat...Restrictions in vicinity of showers/thunderstorms. Tstms
more numerous north, scattered south.

Sun...Restrictions possible near scattered tstms, mainly west.

Monday...Still a chance of showers and storms.




NEAR TERM...Lambert/Fitzgerald
SHORT TERM...Lambert
LONG TERM...Lambert/Martin