Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
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FXUS61 KCTP 291938
Area Forecast Discussion
National Weather Service State College PA
338 PM EDT Sat Apr 29 2017
A nearly stationary frontal boundary will remain over the
forecast area for much of the weekend. A strong Cold front will
move across the region on Monday, followed by cooler air for
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
The leading edge of yet another decaying MCS is moving through
my western zones. Unstable air as measured by CAPE is pretty
much confined to the Mason-Dixon line southward, but RAP
analysis indicates mid level lapse rates are a fairly
respectable 6-7C/km or higher so there is at least some elevated
instability. The HRRR survives these showers as they move
through central and eastern PA through late afternoon, with the
northern 2/3 or so of the region standing the highest chance of
The frontal system over PA is hard to find in the meso anal but
the more humid air over the south seems to be separated by a
boundary that extends from near PIT eastward to near the PA
border and into the soupier dewpoints over the lower Susq.
Satellite loop shows tops warming at a pretty good clip as the
convection leaves the more unstable airmass of the Ohio Valley.
The thin high clouds over the SE have done little to thwart
warming with readings of 80+ already for much of the area.
The latest HRRR takes this MCS and streaks it east and out of
the area by nightfall, with a period of dry weather indicated
into the wee hours of Sunday, before new convection from the
Midwest and OH Valley begin to approach my western areas. I
used blended POPs to bring a small chance of rain back in for
the second half of the overnight. Lows will range from the mid
40s over the north to around 60 over the south. Well above
normal for the last days of April.
.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
The warm front will try to crawl back north into the CWA Sunday
presenting a high temperature forecast problem. Near term
deterministic models show a cool-air damming scenario hanging
rather tough. The surface based LI field is usually a great
indicator of this. The ECMWF/NAM/GFS are all in good agreement
with the warm air working into my western higher elevations
while the ridge-valley areas east of the Alleghenies stay in the
clouds and cooler air. If things work out as expected highs
will vary from around 60 in the Poconos to around 80 in Somerset
Again the main focus for Sunday will be for
showers/thunderstorms to once again develop and/or move into
the region. With the most unstable air expected to be over the
western sliver of my CWA, that`s where I would expect the best
chance for measurable rain. Once again I used blended MOS POPs
for this given that the best focusing mechanism will be well
west of the region.
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
-- Changed Discussion --Upper level ridge builds across the Mid Atlc Region Sunday
night and Monday and a warm front will be lifting through the
Ohio Valley and W PA. This weather feature will lead to
continued chances for showers and even a tsra - mainly in the NW
half of the area. Upper low now over the four corners region is
forecast to lift through the central Plains on Sunday then the
Great Lakes on Monday. This will serve to send pieces of energy
along the surface boundary.
Temps should return/rise to very very warm levels on Monday. The
massive and deepening cyclone lifting into the western Great
Lakes Sun night into Monday will push a strong cold front
through PA Mon into Mon night, accompanied by a round of
potentially potent showers and thunderstorms (likely reaching
western half of CWA in the afternoon and eastern half during the
Once this front passes by much chillier air will advect into PA
on cyclonic flow with unsettled light showery weather persisting
mainly for the northern part of the state right into Wednesday.
Chance for a more widespread light rain arrives Thu into Fri as
a low progged to develop along the southern Appalachians and
the lift northward. Models showing strength/timing issues so
not getting to specific this far out, but looks like unsettled
weather pattern continues.
-- End Changed Discussion --
.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
BFD has seen their ceiling fall to IFR as low level moisture
backs in behind the shallow cold front. The remainder of the
flying area is VFR. A decaying area of showers and thunderstorms
is moving east across the area from about JST-AOO northward.
Terminals will tend to remain VFR with reductions associated
with the showers through late afternoon.
A more general decrease in ceilings will occur this evening and
overnight as cool-moist air settle south behind a weak back door
cold front. The exception will be the lower SUSQ Valley where
ceilings should stay just above 3000`.
Sunday will see conditions improve only slowly over much of
central and northern PA as the warm front tries to return
northward. Scattered showers/thunderstorms will once again be
possible, especially over western areas during the afternoon.
Mon...Breezy. Showers/thunderstorms likely with periods of sub-
Tue-Wed...Breezy with a chance of showers NW.
Thu...Widespread sub-VFR developing ahead of a warm front.
NEAR TERM...La Corte
SHORT TERM...La Corte