Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 201944

Area Forecast Discussion
National Weather Service State College PA
344 PM EDT Fri Oct 20 2017

A large and persistent area of high pressure at the surface and
aloft will remain over the eastern CONUS through the upcoming
weekend. Low pressure is likely to track west of the state early
next week with a trailing cold front and potent upper level
disturbance pushing through Pennsylvania Tuesday or Tuesday
night preceded and accompanied by periods of rain and perhaps a
narrow band of gusty thunderstorms Tuesday afternoon and evening.


Aside from a few wisps of cirrus over the region, full
sunshine is being enjoyed throughout central PA this afternoon.
Clear skies will continue tonight as strong upper ridge expands
northward and center of 1024 mb sfc high slides across central
PA. Light wind will allow mins to drop into the 40s everywhere
with a few upper 30s likely across northern and central valleys
around sunrise. Patchy valley fog will be seen once again a few
hours surrounding daybreak.


Little change in store for Saturday as anomalous upper ridge
delivers yet another splendid autumn day. Abundant sunshine
will allow temps to warm through the 70s most places. Southern
areas could approach the upper 70s.


Upper ridge to start the period with very warm (for October) days
and seasonably cool nights.

Stand-alone shortwave over Gulf States Mon will be overtaken by
a significant digging northern stream trough that will
eventually take on a slightly negative tilt early next week as
it moves from the upper midwest and Miss Valley to the
Appalachian Mtns and Carolina Coast.

Models have converged to indicate the center of the significant
rainfall event occurring late Monday through Tuesday evening
when widespread rainfall amounts of 1-1.5 inches is anticipated.
As the cold front works slowly east across the Commonwealth
Tuesday into Tuesday evening, Sfc-850 mb LIs go slightly
negative acrs parts of Scent PA and the Susq Valley. In addition
to the expansive shield of moderate to briefly heavy rainfall
rates, the pattern appears favorable for a Narrow Cold Frontal
Rainband - NCFRB (with brief gusty winds) to push through as

Then we transition to a period of near to below normal
temperatures for the second half of next week as flow shifts to
the NW as result of upper trough swinging east across the area.
Fair amount of clouds for the NW half of CWA midweek with
scattered lighter showers also poss under the trough. Both GFS
and ECMWF ensemble systems do indicate the thrust of the
chilliest air will be directed west of PA/ And there are
indications of rising heights/milder weather returning again for
the entire eastern conus toward the end of the month.


VFR will prevail through evening, followed by low confidence
for terminal impacts in patchy late- night/early morning valley
fog Saturday morning. VFR conds will prevail throughout


Sat-Sun...Patchy AM valley fog otherwise VFR.

Mon-Tue...VFR to MVFR/IFR. Showers likely; periods of heavy
rain and gusty winds possible with strong FROPA. LLWS.

Wed...Breezy. Sct showers. MVFR NW 1/2.

Thu...No restrictions.


Month-to-date, October 2017 is the warmest October on record at
Harrisburg and Williamsport.




NEAR TERM...DeVoir/Lambert
SHORT TERM...DeVoir/Lambert
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