Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 262018
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
418 PM EDT TUE JUL 26 2016

.SYNOPSIS...
A weak front will remain nearly stationary just south of the
Commonwealth through Wednesday. High pressure will continue
through mid week with warm and dry conditions. An area of low
pressure approaching from the west is likely to lift through the
region on Friday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
The weak cold front south of the Mason Dixon line is acting to
focus some clouds over southern Pa and even a few light showers
just south of the border. RAP meso analysis  shows CAPEs in
excess of 1000J over the border counties, however drier air
filtering slowly southward has led to a decease in dewpoints as
well as the overall CAPE as well.

Warm-dry air aloft should help and keep showers out of the bulk of
the region today into the evening. The HRRR wants to sneak some
remnant midwestern convection into my far swrn zones just after
sundown, but confidence is not high for this and I have very low
POPs as a result.

The overnight will be fair and dry with comfortable humidity over
most of the area. Dewpoints will hang in the mid 60s along the Md
border where a stray shower still be possible.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Rich deep layer moisture will remain pooled south of the Mason
Dixon through Wednesday, providing dry conditions overall. Clouds
will be most prevalent across the south, closest to the  front
and once again, a stray shower or thunderstorm cannot be ruled out
right along the border, especially in the afternoon.

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

&&

.LONG TERM /WEDNESDAY 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 /20Z TUESDAY THROUGH SUNDAY/...
All terminals are VFR and will continue into the overnight before
more patchy fog forms late night into the early hours of
Wednesday. Any areas of late night fog will lift and dissipate
within an hour or so of sunrise.

Southern areas may see a stray shower or thunderstorm pop up in
the afternoon Wednesday.

OUTLOOK...

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

&&


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

&&

$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...La Corte
LONG TERM...Lambert
AVIATION...La Corte



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