Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 152154

Area Forecast Discussion
National Weather Service State College PA
554 PM EDT Wed Aug 15 2018

A ridge of high pressure will slide east across Pennsylvania
bringing a brief break in the relentless widespread rains of
recent weeks. A new cold front will approach the region later
Thursday before passing Friday. Slightly cooler air with more
comfortable humidity will move in for much of the upcoming


Radar loop at 2130Z showing scattered convection developing in
moderately unstable air mass over the mountains north of KIPT.
21Z SPC mesoanalysis indicates mlcape near 1500J/kg across
northeast Pa and there will an increase in large scale forcing
this evening ahead of shortwave approaching from southeast
Ontario. Will therefore maintain low POPs of around 20 pct
through dusk across the northeast portion of the forecast area,
where the best combination of instability and forcing is present.

Passage of shortwave and cooling/stabilizing boundary layer will
result in fair and mild weather overnight. Model soundings and
upstream satellite imagery indicate increasing cirrus overnight
in advance of low pressure tracking up the Mississippi Valley.
How quickly the clouds thicken up will play a role in how much
fog manages to develop. The latest SREF/HREF/NAMNest all
indicate there will be patchy valley fog across the northern
mountains and also over areas east of the Susq River, where the
ground remains so wet.

Can`t rule out a few showers sneaking into the northwest
mountains toward dawn, as waa increases at nose of low level jet
lifting through Ohio.


Clouds will be on the on the increase Thursday as a weakening
cold front and associated shortwave move east from the Grt Lks.
Models agree the upper trough will be shearing out as it moves
into the region. Using a blend of MOS POPs we have the best
chance of showers/thunderstorms over the NW, along axis of low
level jet and associated plume of anomalous pwats. Latest HREFV2
supports the idea of scattered morning showers across the
northwest counties associated with waa at nose of low level jet.
However, diurnal heating of unstable air mass will result in
the best chance of shower/storms during the afternoon hours.

Highs will generally be in the 80s to around 90 over the SE,
still several deg warmer than mid August normals.


Expect an uptick in thunderstorm activity Friday afternoon and
evening as a cold front moves eastward from the Great Lakes/Ohio
Valley. With many areas experiencing near record or record
summer rainfall totals, more heavy downpours will pose an
isolated risk of localized flooding. A few storms with locally
strong to damaging wind gusts are also possible especially
along/east of the Susquehanna River, where SPC now has a
Marginal Risk outlook. Saturated ground will make it easier for
gusty storms to topple trees and cause power outages. The text
HWO was updated to account for the isolated flash flood/severe
storm risk.

A trailing frontal wave of low pressure will continue the threat
of showers/storms across the southern 1/2 to 1/3 of central PA
on Saturday. Sunday into Monday still looks mainly dry under the
influence of high pressure and near-below normal precipitable
water airmass. A spotty P.M. shower or t-storm is possible on
Monday over the southern Alleghenies, as return flow brings
increasing moisture back into the area.

Models and ensemble continue to track a mature cyclone through
the Great Lakes early next week. The well-defined trailing cold
front will trigger T-storms as it crosses the Appalachians on
Tuesday. A severe storm and heavy rain/flash flooding risk will
likely accompany the frontal passage before a push of drier air
delivers a possible stretch of rain-free days later next week.


An isolated shower now and then north of IPT over the higher
terrain. Took VCSH out of IPT. Expect all these to be gone
by 7 PM if not sooner across the higher terrain.

Other than that, nothing going on for a change late this
afternoon. Minor adjustments to the late afternoon TAF updates.

Hazy look is not only high clds, but some smoke aloft from the
western states at times.

Earlier discussion below.

A ridge of high pressure will bring quiet weather to central PA
today. Fog is already burning off rapidly and will yield
widespread VFR before noon.

VFR will dominate the remainder of the day into tonight. High
based cumulus will build across the northern mountains and mid-
Susq Valley late in the day and diurnal heating may just be
enough to kick off an isolated afternoon shower or thunderstorm
there. If an airport takes a direct hit there could be brief
impacts, but the probabilities are too low to include in the
TAFs at this time. In other areas, just expect some scattered

Patchy fog is likely once again late tonight, but thickening
mid/high clouds will limit development.


Thu...Scattered showers/tstms mainly NW half will bring local

Fri...Cold front will bring more numerous showers/tstms areawide
will bring local restrictions. MVFR cigs likely north/west.

Sat...Reductions, esp NW half. Otherwise, isolated/scattered
showers/tstms will bring brief local restrictions.

Sun-Mon...Mainly VFR.



With yesterday`s rain, the State College COOP weather station
at PSU has 20.35", which makes it the wettest summer on record.
The old record was 19.83" in 2003.

Williamsport so far has 22.11" of rain making it the 2nd
wettest summer. The wettest was 1972 with 22.33".

Harrisburg so far has 19.43" of rain making it the 3rd wettest
summer. The wettest was 1972 with 23.33".

Altoona so far has 14.99" of rain making it the 7th wettest
summer. The wettest was 1972 with 17.77".

For ease of record keeping, the meteorological summer runs from
June 1st through August 31st.




NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/La Corte
LONG TERM...Steinbugl
AVIATION...La Corte/Martin
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