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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 231821
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
221 PM EDT Thu May 23 2019

.SYNOPSIS...

A cold front will drop south 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 up fantastic weather for much of the day 
with near normal temperatures and comfortably lower humidity.

&&

.NEAR TERM /THROUGH TONIGHT/...

The line of fast moving convection continues to outrun the 
unstable air and so far the storms have underperformed in what 
was an enhanced outlook for severe storms. The RAP still wants 
to destabilize the SERN zones where a new watch is in effect. 
Shear remains impressive with forecast EHIs/STPs about as high 
as they get for this part of the world.

The big question is if the Lower Susq can destabilize fast
enough to feed these storms that are racing east at 40-50 mph.
The second biggest question will be if new storms can manage to
form over the western and northern parts of the CWA where the
airmass has not been changed and dewpoints remain in the 60s.
 
Different flavors of the HREF have differing solutions with the
most pessimistic member developing a new line and taking until 
about 10PM to have it drop SE to the Mason-Dixon line. Some HREF
members just develop some scattered activity at worst. I 
suspect that unless we see some upstream activity starting to 
spark off very soon, at worst we will see some late afternoon 
scattered activity and the current line will be the main event.

Afternoon high temps will be several deg above normal or in the
mid 70s north and lower to mid 80s in the southern valleys.

What there is of any convection, either left over or yet to 
form, should dwindle early this evening as drier air sweeps into
the forecast area. Lows will drop back into the comfortable 50s
to lower 60s. 

&&

.SHORT TERM /FRIDAY/...

In the wake of the cold front, Friday looks breezy cooler and
drier. 

Highs will be near to slightly above normal in the mid to upper
60s north and mid to upper 70s south. 

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
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 
season.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Scattered showers and thunderstorms into this evening could 
produce brief reductions at central PA TAF sites. Otherwise, 
conditions should generally be VFR.

The threat of showers ends from northwest to southeast late 
this evening, with winds shifting around to the northwest.

Building high pressure will provide VFR conditions Friday under
partly to mostly sunny skies, and a breezy northwest wind could
gust 15-20 mph.

Humidity creeps back in this weekend, and cannot rule out a
scattered t-storm.

.Outlook...

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

Sat...Restrictions possible near scattered tstms, mainly north.

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

Mon-Tues...Generally VFR, although a spotty showers or storm is
possible.

&&

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

&&

$$
SYNOPSIS...La Corte/Lambert
NEAR TERM...La Corte/Lambert
SHORT TERM...La Corte/Lambert
LONG TERM...Lambert/Martin
AVIATION...Evanego