Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 271142
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
742 AM EDT WED JUL 27 2016

.SYNOPSIS...
A weak front will remain along or just to the south of the
Commonwealth through tonight, as high pressure maintains warm and
mainly dry conditions. An area of low pressure approaching from
the west is likely to lift through the region on Friday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
H5 shear axis over wrn and central PA continues to work on deep
layer moisture pooling along and south of the Mason Dixon line to
produce isolated showers. Trailing shortwave now maintaining a
area of sprinkles/light rain showers which will brush parts of the
Laurels and South Central Mountians through 14-15z. Will maintain
slight chc mentions through that timeframe across the southern
tier.

Across central and northern sections...drier air mass in place
will prevent any showers...but clouds will skirt the west central
and central mountains for much of the early to mid morning hours.
Far northern areas will remain mostly clear.

Richest deep layer moisture will remain pooled along and south of
the Maxon Dixon line through tonight. Clouds will be most
prevalent across the south, closest to the front and once again, a
stray afternoon/evening shower or thunderstorm cannot be ruled
out right along the border.

Highs will be a few ticks higher than Tue across the north and
generally unchanged south...and will range from the mid 80s north
to the lower 90s southeast.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
More of the same tonight as deep layer moisture remains pooled
south of the commonwealth. Slight chc pops will be confined to
portions of the southern tier...with decreasing clouds occurring
as one goes north. Mins will range from the upper 50s northwest to
the lower 70s southeast.

Moisture will slowly work northward throughout Thursday as a front
approaches the region from the Ohio Valley and eastern Glaks. Most
areas will remain dry for most of the day...but increasing pops to
sct coverage in the afternoon and evening for most as PW approach
1.5" into the west central and central mountains...and up to 1.8"
over the southern tier. Maxes will range from the lower 80s north
to the lower 90s south.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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-Fri timeframe.

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
shield.

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 rainfl 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
Region.

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 /12Z WEDNESDAY THROUGH SUNDAY/...
Broad, weak high pressure has a little weakness over the southern
tier. VFR clouds there are making a few sprinkles at JST. Just
have a brief VCSH in JST/AOO for the next couple of hours. In
should remain VFR all day. But there is just the slightest chance
of a reduction in visibility due to --RA. BFD, UNV, IPT will be
dry. Heating and a creep northward of the stationary front could
allow isolated convection in the far S later today. A PROB30 may
even be too much. Wind will continue to be calm or just light and
variable. High clouds do expand from SW to NE later tonight. But,
again, should not yield any reductions in vis/cig. Some fog may
occur late tonight.

Mainly zonal flow with just a slight troffiness to it over the OH
Valley then sets up. Moisture gets thicker for the latter half of
the week and remains so through the weekend. Daily heating should
result in sct SHRA/TSRA each afternoon.

OUTLOOK...

THU-SUN...Mainly VFR. SCT PM SHRA/TSRA.

&&

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

&&

$$
SYNOPSIS...DeVoir
NEAR TERM...DeVoir
SHORT TERM...DeVoir
LONG TERM...Lambert/Gartner
AVIATION...Dangelo



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