Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
710 am EDT Friday may 29 2015
a return to warmer and more humid and unsettled conditions will
occur today and continue into Saturday. A cold front will bring a
high chance of showers and thunderstorms to the area later
Saturday. This cold front will take its time crossing the state
with cloudy skies and a chance of showers or thunderstorms continuing
into Sunday. Drier weather and seasonable temperatures are expected
early next week.
Near term /until 6 PM this evening/...
showers still south of the County Warning Area...though hrrr runs show a chance of
showers developing this morning close to the PA/Maryland border.
Otherwise look to more humid conditions by this afternoon as well
as a chance of showers and thunderstorms driven by the daytime
heating...though most of the area should stay dry today. While
severe weather is not expected...any showers will be slow moving
and will put down some localized heavy downpours.
Short term /6 PM this evening through 6 PM Saturday/...
with surface moisture back...a warm and muggy night with lows
mainly in the 60s. Any afternoon showers will quickly diminish by
sunset. Weather pattern becomes active again on Saturday as high
shifts east of County Warning Area and trough begins to move into the region. With
better forcing and the warm and moist boundary layer expect more
widespread showers and thunderstorms Saturday afternoon.
Long term /Saturday night through Thursday/...
probability of precipitation continue high Sat night with approaching cold front. In wake
of the front...a couple days of cloudy...cool and showery weather
appears on tap for central PA with front stalling out south of PA
and a likelihood of overrunning rain/showers. Anomalous easterly
flow/precipitable waters indicated in gefs over central PA between surface high over
new eng and front to the south. In addition to the
moisture...central PA will remain in favorable jet entrance region
sun-Mon..providing the lg scale forcing to support periods of much
needed rain sun. Drying trend begins Monday with several days of
comfortable temperature and humidity levels and lower probability of precipitation.
Aviation /12z Friday through Tuesday/...
surface high pressure and associated area of below normal precipitable water air of
just 0.50 of an inch will lead to mainly sunny...warm conditions
through early this afternoon with comfortable humidity. Quasi
stationary from just south of the Mason Dixon line will drift back to
the north into Penn today /first into the western mountains...where precipitable waters
will bounce back quickly to around 1.5 inches by late this
Aside from some patchy MVFR conditions in fog through about
12z....VFR is expected to continue at most airfields for much of
As moisture and corresponding convective available potential energy increase to around 1500-2000
j/kg across the western third of the state this afternoon...
scattered thunderstorms and rain will develop in the 18-20z timeframe...and become
most numerous between 20-01z Saturday.
With 6 km bulk shear under 20kts...and the shear profile fairly
linear from the southwest in the 3-18kft above ground level layer...multi-cell
clusters/short lines of thunderstorms and rain with brief wind gusts of 40-50 miles per hour
are possible along with a few instances of at least small hail.
Brief MVFR...to possibly IFR will accompany the thunderstorms and rain across our
western taf sites later this afternoon and this evening. High res
rapid refresh model indicates the eastern extent of the
convection /shra and thunderstorms and rain/ making it a kelz to kunv and khgr line
around 00z Sat...then fizzling out due to the absence of any
significant shortwave energy.
Have vcsh mentioned for kbfd and kjst around and after 19z.
Variable amounts of stratocu and altocu will be around tonight in
the broad warm advection and high precipitable water air well ahead of an
approaching cold front. Spotty showers and perhaps a brief thunderstorms and rain
will be around tonight. Areas of MVFR ceilings and visibilities are
possible...mainly after 04z Saturday.
More numerous showers and thunderstorms and rain will fire during the afternoon
Saturday...in the heat and high humidity ahead of the cold
front...and along a weak Lee trough over...and just west of the
Sat...patchy MVFR fog/ceilings early. Scattered-numerous afternoon thunderstorms west/cold
frontal passage late Sat northwest...and Sat night central and southeast PA.
Sun-Tue...VFR/MVFR conds with scattered showers/tstms.