Scientific Forecaster Discussion
fxus61 kctp 251957
Area forecast discussion
National Weather Service State College PA
357 PM EDT Thu may 25 2017
mostly cloudy skies with scattered showers will persist into the
evening hours. A few strong thunderstorms are possible, mainly
across south- central and southwestern PA. Scattered showers
will linger into Friday followed by a period of mainly dry
conditions Friday night into Saturday. Showers and thunderstorms
will likely impact the area Sunday into Memorial Day. Today
will be the coolest day this week with temperatures rebounding
through the Holiday weekend.
Near term /until 6 am Friday morning/...
back end of double barreled surface low pressure system will
lift north through the area overnight. Sfc cyclonic flow under
cold upper core aloft will support scattered rain shower into
the early overnight, especially western sections early this
evening. Srn third to half of the County Warning Area remains in a marginal
outlook for severe thunderstorms through this evening.
Short term /6 am Friday morning through 6 PM Friday/...
broad cyclonic/west-northwest flow on southern end of exiting
upper trough will support terrain-enhanced showers on Friday
before precip winds down Friday night/am Saturday.
Long term /Friday night through Thursday/...
a lower-amplitude but moderately strong westerly (zonal) mid
level flow will set up in the wake of the departing upper trough
with modest height rises/weak will ridging aloft into the
weekend. A warm front is progged to extend east from surface low
in the western Ohio Valley to the mid-Atlantic coast on
Central PA should reside on the North/East fringe of high
instability convective corridor/mesoscale convective system type pattern expected to
evolve from the central and Southern Plains to the southern mid-
Atlantic coast into Saturday night. The greatest risk for
scattered thunderstorms remains over the SW 1/3 of the County Warning Area
which is consistent with previous fcsts. Storm Prediction Center has introduced a
marginal risk into this area for d3. The remainder of the area
should see a mainly dry start to the Holiday weekend but will
maintain slight chance pops.
The large scale pattern will evolve into a broadly cyclonic
flow regime by Monday with upper trough parked over the Great
Lakes and southeast Canada into midweek. The aforementioned warm
front will lift north across the area on Sunday followed by a
series of weaker cold front associated with shortwave trough
rotating around parent upper low centered to the south of Hudson
Bay. Ensemble blend still supports Max pops on Sunday/Sunday
night into Monday with some additional shower opportunities into
midweek as series of shortwaves rotate around mean upper
trough. Temps should average pretty close to normal/seasonal to
close out the month of may.
Aviation /20z Thursday through Tuesday/...
primary surface low pressure (995 mb) was located over Ohio
early this afternoon and is nearly stacked with its parent upper
low. A few disturbances rotating around its base will lift
northeast twd Pennsylvania last this afternoon and
evening...returning a couple of rounds of showers (and
isolated-sct thunderstorms and rain across the SW third- half of the state after
Widespread IFR/low MVFR cigs will continue across central PA and
the susq valley through the mid-late afternoon, with gradual
improvement across at least the western taf sites as an
occluded front lifts NE across that region with some drier air
aloft in its wake along with a gradual veering of the wind to
the southwest, then west at kjst,kaoo kunv and kbfd late this
afternoon and this evening.
The drying aloft, and some breaks in the dual-multi layered
cloud deck, will help to create some MDT instability for the
chc of a thunderstorms and rain. Mentioned thunderstorms in the vicinity at kjst, kaoo and kunv, in the
MVFR to IFR cigs will likely linger in many locations tonight
with vsbys dipping back to MVFR at most taf sites.
Cooler air advecting in aloft, combined with deep moisture and
a favorable westerly upslope component over the western mtns
and Laurel Highlands will lead to periods of LIFR/vlifr cigs and
IFR to ocnl LIFR vsbys at kjst and kbfd.
Across eastern PA, light wind, wet ground and light winds could
result in areas of LIFR fog forming late tonight.
After some areas of low cigs and fog early in the day Friday,
the afternoon will feature mainly VFR cigs with brief MVFR to
IFR cigs and vsbys in isolated-scattered showers...mainly after
16z. Moist west-northwest upslope flow continues across the western mtns
with the best potential for IFR in sctd showers.
Fri...am low cigs/showers likely bfd/jst.
Sat...am fog possible bfd.
Sun...showers/reduced cigs possible, esp Sun night.
Mon and Tue...am low cigs poss west. Sct PM tsra impacts poss