Scientific Forecaster Discussion
fxus61 kctp 211021
Area forecast discussion
National Weather Service State College PA
621 am EDT Fri Jul 21 2017
Pennsylvania will be on the northern periphery of a subtropical
ridge passing across the southern states through the weekend.
A slow moving cold front will push through the area early next
Near term /until 6 PM this evening/...
satellite loop at 09z showing fairly widespread low clouds and
fog across the alleghenies. Model soundings indicate this low
level moisture will mix out to a sct-bkn cu field by late
morning. Large scale subsidence and arrival of much lower pwats
should result in a rain free Friday for most if not all of the
forecast area. However, will maintain a slight chance of an
afternoon thunderstorm near the Mason Dixon line, which will
remain on northern edge of ring of fire.
Gefs mean 850 temps still around 18c today, which should
translate to Max temps from the mid 80s over the northern
mountains, to the low 90s in the susq valley. The southeast
counties fell just short of heat advisory criteria yesterday and
expect a similar scenario today with heat indices over that
part of the state peaking in the upper 90s.
Short term /6 PM this evening through 6 PM Saturday/...
any isolated diurnally-driven showers/storms along the southern
tier should die out around sunset. Otherwise, all model
guidance supporting a dry forecast tonight, as weak surface
ridge passes over PA.
Concern remains for possible severe weather Saturday PM, as warm
front pushes into the region ahead low pressure over the grt
lks. Extensive cloud cover associated with warm front will
likely result in limited cape Saturday as the 00z gefs shows.
However, a powerful low level jet and plume of anomalous pwats
is progged to work through the area Sat night. Convection
associated with this feature could potentially evolve into an
mesoscale convective system with potential for overnight severe weather in central PA.
Long term /Saturday night through Thursday/...
favorable scenario for additional severe weather across central
PA Sunday as the region will be within warm sector south of
anomalous surface low tracking eastward along the PA/New York border.
Moderate convective available potential energy and moderate westerly flow aloft, combined with
large scale forcing ahead of approaching upper trough, should
support widespread convection by afternoon.
Some uncertainty 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 /10z Friday through Tuesday/...
lower susq remains VFR, but fairly widespread low clouds and
fog across the western portion of County Warning Area (allegheny front) early
this morning - with IFR conditions extending from bfd-jst and
MVFR working into the central mtn sites of aoo-unv. Model
soundings indicate this low level moisture will mix out to a
sct-bkn VFR cu field by mid-late morning - likely lingering the
longest at jst.
Large scale subsidence expected to result in a rain-free Friday
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
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.
Sat...am valley fog possible. Thunderstorms and rain/rain showers likely with
Sun...am valley fog likely. Cig restrictions likely north.
Thunderstorms and rain/rain showers likely with intermittant impacts.
Sun night...cig restrictions likely. Scattered tsra/shra.
Mon...am restrictions likely. Scattered thunderstorms and rain.
Tue...patchy am fog. Otherwise no sig wx.