Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
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FXUS61 KCTP 280639
Area Forecast Discussion
National Weather Service State College PA
239 AM EDT THU JUL 28 2016
A weak trough to our north and the subtropical ridge to our south
have setup a frontal boundary just to our south. This boundary
will move northward as a shortwave moves over the ridge Thursday
night. This should produce some rain Thursday into Friday. Behind
this system system slightly cooler air aloft moves over the
region. But the ridge may begin to build to our west again early
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Moisture and clouds slowly increasing from the southwest overnight
with showers increasing over the Laurels through the pre dawn
hours. Overnight lows mainly near 60 in northwest to lower 70s
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/...
Tomorrow clouds increase in southern and central areas. Increased
moisture will produce haze. Best chance rain in southwestern
areas. Chance of rain will increase southwest to northeast during
the day. But most guidance continues to imply most of northern PA
should be rain free most of the day. Best chance in south and
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
In the medium to long-range period...conditions slowly revert to
near normal in temp and precip as several chunks of short wave
energy in the westerly flow aloft helps to carve out a mean 500 mb
trough axis over the Glakes and Ohio Valley region during the Thu-
The peak in unsettled weather (with perhaps some periods of down-
right rainy conditions) occurs Thursday night and Friday as a
well-defined wave of sfc-850 mb low pressure lifts ENE out of the
Ohio Valley and heads across the I-95 Megalopolis.
Followed a blend of EC/GEFS/superblend and NBM guidance for that
particular 24-36 hour period to arrive at likely pops for rain and
scattered TSRA. Some uncertainty in timing and areal coverage of
the convection led us to undercut the NBM by 10-20 percent for
now, recognizing issues with large scale model convective
parameterization schemes (and subsequent exaggeration of the areal
coverage and broader qpf amounts) means that we`ll likely see more
concentrated areas/bands of heavy convection, compared to the
model depicted, larger cold season stratiform look to the precip
Portions of Southern and Central PA...close to the track of the
1006-1008 mb sfc low will likely see some localized heavy 1-2
inch,12-24 hour rainfall amounts by Friday afternoon...with even
the potential for some pinpoint heavier amounts from embedded
TSRA, as a tongue of 2 inch pwat air lifts north and wraps
cyclonically into sern PA and the Lower Susq Valley.
For later Friday through the upcoming weekend, a large area of
high pressure (1020-1024 mb) near the border of southern Quebec
and Ontario will try to push drier air south into the Mid Atlantic
Another...apparently weaker wave of low pressure at the sfc and
aloft lifts NE out of the Ohio Valley over the weekend and brings
an enhanced chc for showers. Slight diffs in timing/location exist
between the EC/GEFS and NBM guidance. However...the target period
for the best chc of showers and isolated to sctd TSRA appears to
be late Sat into Sunday.
Afterward, heights begin to rise from the southwest, accompanied
by a ridge of surface high pressure building east into PA with
mainly dry conditions and a rebound in temps for early next week.
.AVIATION /07Z THURSDAY THROUGH MONDAY/...
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Some mid and high clds across the sw. Isolated showers along
the MD line.
Earlier discussion below.
VFR conditions across the region this evening. Expecting some
fog to develop overnight...affecting most airfields with MVFR
conditions. IFR conditions were introduced int KBFD TAF,
following the lead of what`s happened there for the last several
nights, with a low IFR stratus deck developing in the pre-dawn
Morning fog/haze will lift early Thursday. Showers and isolated
thunderstorms could move into the area from the southwest.
With POPs generally less than 50 percent, and scattered nature of
the rain, have left out of TAFs except for a VCSH in KJST for now.
More restrictions possible overnight Thursday into Friday with
the potential for rain and thunderstorms along with fog.
Conditions expected to improve Friday into the weekend.
FRI...Some restrictions in SHRA/TSRA and patchy fog...mainly
SAT-MON...Wide range of conditions expected with a chance
of showers and storms.
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