-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 172327
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
727 PM EDT Thu Aug 17 2017

.SYNOPSIS...
A warm front will push northward across the region this evening
and overnight and a cold front will push across on Friday.
Numerous showers and thunderstorms will result, and some could
be severe later tonight and during the day. After the cold front
passes, the air will dry out and fair weather will follow for
the weekend and into the new week.

&&

.NEAR TERM /UNTIL 7 AM FRIDAY MORNING/...
Minor updates with new data and HRRR to show the potential for
where the showers and thunderstorms maybe.

Key points going to be a rather warm and muggy overnight. Dew
points mainly in the upper 60s and lower 70s.

Radar and satellite show most of the showers to our west. Around
7 PM there was one one weakly rotating storm in northwest Warren
County. So we have had rain, at least somewhere.

There is a modest line the HRRR develops and brings into central
PA overnight. It implies a few cores could produce 1-2 inches of
rain. But few and far between.

Satellite shows coldest clouds over Ohio. Best chance of rain
will be in western half. HRRR implies some showers over western
areas of the morning commute.

&&

.SHORT TERM /7 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Updated grids for latest guidance. Still have CAPE in the east
and some strong winds. Thus cannot rule out some deeper cored
showers/thunderstorms in the afternoon.

The HRRR and GEFS both show winds go more westerly early in
western PA and 850 hPa temps and PW drop. The front will be
improving the weather west to east from mid-morning onward.

The PW and CAPE imply showers and storms should develop around
mid-day close to the KJST-KAOO-KUNV area and moved east. GFS
CAPE is well into the 1800 to 2400 JKG-1 area. CAPE values and
PW values drop fast even in the east where they plummet just
after 0000 UTC. Could be a few strong to severe storms in the 18
to 23 UTC timeframe.

So improving weather later afternoon and evening in the east.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
We should remain relatively dry as the PW values stay near
normal until perhaps Tuesday. This said there are hints of a
weak wave and scattered showers perhaps Sunday.

Tuesday could be rather warm as there is a surge of above
normal 850 hPa temperatures and PW values above normal. Not
surprisingly the GEFS shows higher POPS Tuesday afternoon into
Wednesday with the wave and front.

We should enter the second half of the weak in a cooler and
drier air mass as currently forecast. And thus in the grids.

Bottom line in this period the NCEP guidance suggests low
probability of significant QPF.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...

-- Changed Discussion --
Most of the shower and thunderstorm activity remains well to our
west. There is a weakening thunderstorm northwest of KBFD.
Cannot rule our brief lowering cig/vis at KBFD with showers and
storms moving east to the west.

A few larger storms have developed to the southwest along the
PA/OH border.

More impressive storms are over southeast Ohio. At this time
most of this should pass well south of KJST/KAOO. HRRR implies
some overnight showers in SW PA. VCSH in TAFS

Expect some lower CIG/VIS in the very warm humid airmass by 0600
UTC at most locations. Some reductions in VSBY likely. Things
improve after sunrise. But there is a chance of showers and
stronger thunderstorms developing in the 15 to 1800 UTC window
on Friday in W-central areas then moving east.

Things improve late Friday evening and Saturday behind the
frontal boundary that will trigger the showers.

.OUTLOOK...

Sat-Mon...No sig wx.

Tue...SHRA/TSRA poss.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...Dangelo
NEAR TERM...Grumm
SHORT TERM...Grumm
LONG TERM...Grumm/Lambert
AVIATION...Grumm/Fitzgerald