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Area forecast discussion 
National Weather Service State College PA
1134 am EST Thursday Nov 27 2014

Synopsis...
a weak upper air disturbance will keep clouds and the chance of a
few light snow showers in the forecast today and Friday.
Temperatures will begin to moderate this weekend as high pressure
moves off the southeast coast.

&&

Near term /through tonight/...
this mornings surface analysis shows a weak surface low over North
Carolina and a surface trough extending northward into PA...supported by
several shortwaves swinging east from the Tennessee Valley. This
energy and resulting surface convergence/upslope flow is forcing an
area of light snow across the northern and central mountains that will
affect parts of central PA into early afternoon. As support moves east
of the mountains...expect downsloping to limit coverage of the snow.

Do not expect significant snow accums with but could be enoughto
coat roads and cause some slipper spots...so have updated
phlhwoctp to give the public/customers a heads up.

Highs today will range from the upper 20s over the north to middle
30s over the south...which will average around 10 degree below
normal.

Biggest question for later today into the overnight will be
whether a period of more organized lake effect can gather itself
over northwestern areas. Deep layer flow does look favorable for a time
tonight...but relatively short over-lake trajectories should
limit snowfall to mainly sub advisory levels.

&&

Short term /Friday/...
inversion heights are expected to lower Friday which should put a
damper on any of the best developed lake effect bands...but clouds
and perhaps a few snow showers will remain possible over the
normal western and northern locations. The best chances will be
in the morning...with brightening skies likely in the afternoon.

Highs will be a few degree cooler than today as the core of the Post
frontal cold air settles overhead.

&&

Long term /Friday night through Wednesday/...
anomalously low heights over the eastern US early in the period
will flatten out into a broad zonal flow during the weekend. This
will prompt a warm-up as the cyclone track shifts to our north and
high pressure moves off to our southeast.

The cold Post frontal airmass will begin moderating by
Saturday...with readings reaching the mild range by Sunday.

Models which were in decent agreement on the approach of a front
for Monday...now have differences in dropping a weak cold front
through the area early next week. The GFS/gefs are faster and have
high pressure building in for Monday...while the European model (ecmwf) slows its
frontal passage down by at least 12 hours. Given the flat fast
flow...such differences are not unexpected. While the front will
represent the best chance for organized precipitation and the passage
time is uncertain...zonal flow will make for a lack of moisture
keeping quantitative precipitation forecast be on the light side.

One area of possible concern could be the expected development of
some light warm advection precipitation Saturday night into Sunday
morning. Temperatures aloft warm rapidly...and I kept forecast surface
mins mainly above freezing. But if we end up a few degree cooler...we
could see a period of some light icing until temperatures can
recover Sunday.

The expected warm up over the weekend into early next week should
go a long way toward erasing the snow that blanketed the region
yesterday.

&&

Aviation /15z Thursday through Monday/...
late morning surface analysis shows a weak surface low over North
Carolina and a surface trough extending northward into PA...supported by
several shortwaves swinging east from the Tennessee Valley. This
energy and resulting surface convergence/upslope flow is forcing an
area of light snow across the northern and central mountains that will
affect parts of central PA into early afternoon. As support moves east
of the mountains...expect downsloping to limit coverage of the snow.

The light snow will lead to MVFR visibilities and IFR ceilings at western and
central airfields. A few periods of IFR ceilings are also possible.

Elsewhere...the few degree c inversion between 4-5 kft above ground level...and the
relatively light northwest beneath this stable layer...will make for a
rather hazy/stagnant late morning to early afternoon.

The northwest breeze will pick up a bit after 15z...helping to mix out
and erode the lower stratus bases across much of the alleghenies.
However...moist upslope flow /nearly orthoginal to the western PA
ridges/...and deepening of the cold air will lead to a gradual
increase in snow showers this afternoon and evening with periods
of IFR/LIFR likely at kbfd and kjst after 21z.

Later this afternoon expect plenty of strato cumulus /topped by a layer or
two of altocu and cirrus/ and relatively light northwest winds through
18-21z today with just some isolated to scattered snow showers
across the northwest mountains and Laurel Highlands /from kbfd to kjst/.

Some lake effect -shsn are forecast to develop late this afternoon
through tonight over the western 1/3 where reduced conds are likely to
persist. Coinciding with the snow showers...will be an increase in
the northwest winds and associated gusts.

Late day/night-time winds should gust in excess of 20kts across
the mountains of western Penn...while gusts elsewhere will likely be in
the middle to upper teens - mainly this afternoon and evening.

Outlook...

Tonight...IFR/MVFR with occasional -shsn western 1/3. VFR to MVFR ceilings
cntrl/east.

Friday...am MVFR/-shsn northwest...otherwise becoming VFR.

Sat-sun...mainly VFR. Isolated -shra possible.

Monday...cold frontal passage. Mainly VFR. Scattered -shra possible.

&&

Ctp watches/warnings/advisories...
none.

&&

$$
Synopsis...la corte
near term...la corte/gartner
short term...la corte
long term...la corte
aviation...Lambert/gartner

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