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000
FXUS61 KCTP 211951
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
351 PM EDT Fri Jul 21 2017

.SYNOPSIS...
Pennsylvania will be on the northern periphery of a subtropical
ridge passing across the southern states through the weekend.
A few rounds of showers and thunderstorms are expected both
Saturday and Sunday, and some could produce gusty winds, hail
and heavy downpours. Another cold front will push through the
area early next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Weakening MCS traversing WV and approaching the WV and MD
panhandles at mid afternoon. PW pooling around 2" along the
Mason Dixon line and slowly lifting northward should bring
isolated to scattered coverage of showers and thunderstorms
through this evening across my southern tier counties (Laurel
Highlands and South Central Mountains), with mainly dry
conditions expected elsewhere.

remnants of aforementioned MCS track off the mid Atlantic
coastline later this evening, and any diurnally-driven
showers or storms along the southern tier should die out around
sunset. Weak surface ridge passes over PA tonight bringing fair
weather and mins ranging from the upper 50s north to around 70
southeast.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Large MCS forms upstream overnight and approaches eastern OH in
the pre dawn hours Saturday morning. This feature will be the
main player for potential severe weather on Saturday, as strong
moisture flux and increasing boundary layer convergence point
increase the likelihood of strong to severe storms over PA by
late morning and afternoon.

CAMs differ on timing and strength of MCS evolution ranging from
as early as late morning into my western zones to as late as mid
to late afternoon. Think the former is more likely...given quick
moisture return late tonight and Saturday ahead of the
approaching complex. Warm front pushing into the region on
Saturday will also tend to favor lower LCLs and sufficient shear
for rotating updrafts. Farther north, extensive cloud cover
associated with the warm front will likely result in limited
CAPE Saturday as the 00Z GEFS shows.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
A second round of convection is possible Sat night as strong
low level jet and plume of anomalous PWATs works through the
area. Convection associated with this feature could potentially
evolve into another MCS with potential for overnight severe
weather in central PA into Sunday morning.

Favorable scenario for additional severe weather across central
Pa during the daylight hours Sunday as the region will be
within warm sector south of anomalous surface low tracking
eastward along the PA/NY border. Moderate CAPES and moderate
westerly flow aloft, combined with large scale forcing ahead of
approaching upper trough, should support widespread convection
by afternoon.

Some uncertainty continues with regards to timing of upper
trough passage early next week, but additional showers/storms
appear possible. A period of dry and cooler weather appears very
likely by midweek, as upper trough axis finally passes east of
Pa and surface high builds into the area.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Large scale subsidence bringing a rain-free afternoon for most,
though slight chance for an afternoon thunderstorm will persist
across southern mtns in deeper moisture.

Quiet night tonight, with most locales remaining VFR, though the
usual spiderweb of valley fog will settle into the western and
northern mtns.

Warm front pushes into the region on Sat followed by an upper
trough on Sun, which will keep numerous showers and
thunderstorms around over the weekend.


.OUTLOOK...

Sat...AM valley fog possible. TSRA/SHRA likely with
intermittent impacts.

Sun...AM valley fog likely. Cig restrictions likely north.
TSRA/SHRA likely with intermittent impacts.

Sun night...Cig restrictions likely. Scattered TSRA/SHRA.

Mon...AM restrictions likely. Scattered TSRA.

Tue-Wed...Patchy AM fog. Otherwise no sig wx.

&&

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

&&

$$
SYNOPSIS...DeVoir
NEAR TERM...DeVoir
SHORT TERM...DeVoir
LONG TERM...Fitzgerald/Gartner
AVIATION...Jung/DeVoir/RXR