Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 290539
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
139 AM EDT Sat Apr 29 2017

.SYNOPSIS...
A nearly stationary frontal boundary will be located over the
Keystone state for much of the time this weekend. A few
disturbances aloft will move over this front and bring periods
of showers and thunderstorms. A strong trough and cold front
will move across the region on Monday, followed by much cooler
temperatures.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Northeast extent of a series of MCSs (stretched all the way back
to the southern plains) will move across the CWA early today
bringing a several hour period of MDT to ocnly HVY rain (with
embedded TSRA across the southern few layers of counties).

Rainfall amounts should average around one inch across the
south...near or slightly under 0.75 of an inch along the I-80
corridor, with 0.25 of an inch or less along the PA/NY border.

Overnight, lows will range from the mid 50s across the NW...to
the mid 60s across the Lower Susq Valley (that current lies just
to the SE of the stalled out frontal boundary). These temps will
be about 15-20 deg above normal.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
Guidance agrees in bringing the warm front slowly northward
today, but differences exist as to how far north it manages to
progress. Warm and muggy air will pool along and just to the
south of the boundary. Models develop a fair amount of CAPE,
they just differ on whether the most unstable air will favor the
Maryland border areas or extend up into the Central Mountains.
SPC has the region under a marginal risk for severe storms, and
with moderate deep layer shear expected, this looks reasonable.
Look for the best chance of showers and storms to be from mid
day into the afternoon.

Highs will vary from around 70 along the NY border to the
mid/upper 80s over the SE. If we end up with more sunshine than
currently expected, I would not rule out a high temp near 90 in
a couple of places. With dewpoints well up into the 60s over at
least the southern half of the CWA, it will begin to feel humid.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Upper level ridge tries to builds in for Saturday night through
Sunday but continued southerly flow/instability and a weak warm
front lifting through the Ohio Valley and W PA will lead to
continued chances for showers and even a tsra - mainly in the
NW half of the area.

Temps remain very warm into Monday. A 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 evening).

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
lift northward. Models showing strength/timing issues so not
getting to specific this far out, but looks like unsettled
weather pattern continues.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
Complex weather pattern across the region. Radar and short term
models indicate area of showers/rain moving in from the west.
Although there is some embedded thunder, it seems to be having
difficulty making it over the western mountains. Have increased
rain chances in TAFS over the next 2 to 4 hours. With dry
atmosphere in place, have not included restrictions in flying
conditions (cigs/vsby), although there may be some isolated
restrictions in heavier showers/thunderstorms. Short term models
indicate that most of the shower activity will diminish before
sunrise.

A wavering frontal boundary is expected to set up across the
region tomorrow. Thinking right now for aviation purposes is to
lean towards northern areas to be in the cool sector, with
occasional showers and lower ceilings and less chance of
thunder. Central areas are in the battleground region. Scattered
showers and thunderstorms possible right through the period.
Reluctantly, have included VCTS for large blocks of time in the
forecasts, as timing very difficult. Southeastern areas may be
in the warm sector Saturday. While there is a risk of thunder
here as well at KMDT and KLNS, activity may be more isolated
than across the KJST/KAOO/KUNV corridor. Have therefore left
thunder out of these (KMDT/KLNS)TAFs for now.

Outlook...

Sat-Sun...Sct showers/Tstorms. Areas of sub-VFR north, and also
associated with any thunderstorms.

Mon...Breezy. Showers/thunderstorms likely with periods of sub-
VFR. FROPA.

Tue-Wed...Breezy with a chance of showers NW 1/2.

&&

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

&&

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


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