Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 251206
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
806 AM EDT Tue Sep 25 2018

.SYNOPSIS...
Southerly flow and a disturbance aloft will keep damp conditions
in place through Wednesday when a cold front is expected to
sweep through the region. Cooler and drier air will make a
return for Thursday into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Radar shows a large area of light to moderate rain lifting
through the region fueled by a mid level shortwave that shows
up nicely on water vapor imagery. Strong warm advection on the
face of a broad southerly 40-50kt low level jet will tend to max
out by sunrise as the core of LLJ lifts through NY state. This
will lead to the steady rain becoming more showery with even the
chance of some thunder as the cool air damming mixes out and we
see a modest erosion in stability. Convective parameters are
not expected to be especially impressive this afternoon so the
chances for severe storms will be minimal.

After a relatively cool day today, it will be a mild overnight
with temperatures hanging in the 60s. Most places will average
15-20 deg warmer than normal. Weak forcing and marginal
instability could help trigger a few showers but widespread rain
is not expected.

&&

.SHORT TERM /WEDNESDAY/...
A cold front will move through the area Wednesday. Latest timing
shows the front moving into my central zones by 18Z/2PM,
hinting that maybe the severe threat for the western zones
might be diminished somewhat by the early FROPA. The SREF and
GEFS/GFS all suggest this scenario painting the best CAPE of the
day over SERN areas during the afternoon. Only the ECMWF is
more generous with its CAPE forecast despite agreeing on the
frontal timing.

SPC places all of Central PA in a slight risk for severe with
potential for a squall line to develop with local bowing
segments likely. Some fine tuning of the western portion may
need to be done if later model runs confirm the frontal timing.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The front will slow and stall over the Mid Atlantic states which
always inserts a fair amount of uncertainty to the forecast over
the southern counties as weak waves along the front skirt the
southern parts of the CWA with showers. I used a model blended
MOS to keep the region mostly dry Thursday and Friday, but
wouldn`t be surprised if this changes with later model guidance.

A cold front is made to approach the area for Saturday, but
models keep it weak with the GFS washing it out almost entirely.
I chose the optimistic route and only introduced very small
chances for showers and mainly over the north.


Once the front passes Wednesday, cooler and drier air will make
a return, with temperatures remaining a few deg either side of
normal into the weekend.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...

A warm front lifting northeast from the Ohio Valley will keep
MVFR to IFR cigs over the region through the first half of the
day.

A core of strong winds aloft lifting through the area this
morning. Latest models have LLWS moving through 15Z. Wind shear
is strongest now with it slacking by late morning and should be
out of the region by 18Z.

Low cigs and rain will continue through a good portion of the
day. Improving conditions moving in slowly. Expect cigs and
vsbys to improve from southwest to northeast as the warm front
pushes through the region. SREF/HREF support cigs rising to mvfr
across much of southern Pa by afternoon, while the northern
mountains likely remain IFR. Shifting winds to the south at
KJST typically results in vfr conditions, as the flow descends
higher terrain to the south, so the best flying conditions will
likely be there on Tuesday.

.Outlook...

Wed...AM low cigs/fog possible. Afternoon tsra impacts possible.

Thu...Patchy AM valley fog possible northwest Pa.

Fri-Sat...No sig wx expected.

&&

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

&&

$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...La Corte
LONG TERM...La Corte
AVIATION...Fitzgerald/Ceru


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