Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 191150

Area Forecast Discussion
National Weather Service State College PA
650 AM EST Thu Jan 19 2017

High pressure will build northeast across Pennsylvania today,
providing dry conditions through early Friday. Low pressure over
the midwest will push a warm front north across the commonwealth
during the day Friday bringing a several hour period of steady
rain. Relatively mild conditions will persist for the next
several days.


Another night/early morning spent under an extensive blanket of
low clouds and patchy light fog, as lowering inversion will keep
llvl moisture trapped beneath it for much of central PA.

Most places will see a 5-8 kt west to west-northwest breeze
through the mid morning with some gusts into the mid and upper
teens across the NW mtns and Laurel Highlands.

Min temps will be fairly homogeneous...ranging from the lower to
middle 30s throughout Northern and western PA to near 40F in the
larger metro areas across the lower Susq Valley.

Subsidence inversion base lowers by about 1000 feet throughout
today which should yield some breaks in the increasingly shallow
strato cu deck. High temps today will be in the lower-mid 40s
across the Northern and Western Mtns, and 45 to 50F from the
Central mtns to the Lower Susq Valley.


1020 MB sfc ridge builds NE and over central PA and upstate New
York late today and tonight as a sharp upper ridge builds over
the NE states (sliding from the spine of the Appalachians to the
Eastern Seaboard by midday Friday).

The first half of tonight will start off partly to mostly cloudy,
then turn overcast in many places by 12Z Friday.

The main weather maker for early in this period will come in the
form of a warm front that will lift north over the state during
the day Friday. Operational model and EFS consensus us for a few
periods of rain to occur Friday - primarily during the daylight
hours as the nose of a 35-40 kt south-swrly LLJ helps to
transport a few bands of relatively strong 925-850 mb Theta-E
convergence and uvvel over the state.

Consensus Model QPF ranging from 1-2 tenths of an inch across the
Mtns north and east of KIPT, to between 3 and 4 tenths of an inch
in the SW agrees well with the concept categorical - 100 percent
pops in our gridded forecast (and depicted by the latest several
runs of the NBM).


The upper ridge is forecast to re-establish itself over the
eastern U.S. over the upcoming weekend, bringing mild and mainly
dry conditions Saturday, through at least the mid morning hours on

Daytime temperatures across most of Central Pennsylvania will be
well above normal, but the departures for overnight lows should be
greater by several degrees more throughout the entire extended

The ridge axis will shift to the Hudson Valley and Eastern
Seaboard early Sunday as a sfc backdoor cold front drifts swwd
into PA and stalls out as a potent and moisture laden nearly
stacked low lifts NE from the deep south to the Delmarva region by
12Z Tuesday.

Temps could be marginal at the start of pcpn overnight Sunday for
some ice or snow, and soundings via the GFS/GEFS and EC appear
cold enough for Sunday night through Monday night for a mix of
rain/snow (or even periods of all wet snow at times across the
northern mtns of PA). However, the bulk of pcpn across the
Central Ridge and Valley Region looks to be rain at this point
through Monday afternoon.

The trend in most operational models and ensembles has been
further to the south and east with this particular late
weekend/early week system. This places parts of the fcst area in
the sweet spot for potentially several inches or more of heavy,
wet snow (especially later Monday/Monday night across the nrn and
wrn mtns of PA at elevations of 1400 ft or higher), as the mean
850 mb low in the GEFS and EC tracks NE along the I-95 corridor in
VA and adjacent SERN PA/Southern NJ.

U-wind anomaly at 850 mb peaks at -4 to -5 sigma during much of
Monday as a 45-55kt easterly llj develops between this approaching
low, and the aforementioned colder airmass pushing swwd from SERN
Canada and the New England states. Rainfall amounts are expected
to be in the 1 - 1.5 inch range across roughly the SE half of PA
with lesser amounts to the NW.

Another short wave ridge will slide east from the Ohio Valley and
move over the Commonwealth Wednesday, accompanied by light wind
and fair/generally dry conditions.


Strong inversion will keep lower clouds across the region
early on today.

Partial clearing late, but high clouds will not be that far off.

Looks like any rain on Friday will be after sunrise.


Fri...Restrictions developing early. Rain/Snow north and rain
south early. Rain areawide in the afternoon.

Fri night...Widespread restrictions in areas of drizzle.

Sat...MVFR/VFR cigs.

Sun...Widespread IFR/MVFR restrictions. RA advances fm S-N.

Mon...Widespread IFR restrictions in -RA. LLWS poss.




NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Lambert
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