Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
827 PM EDT Friday Jul 25 2014
shower and thunderstorm chances are returning for the weekend.
Colder weather can be expected next week.
Near term /until 6 am Saturday morning/...
a weak short wave approaching from the northwest will slowly
increase clouds through the remainder of the evening...however a
lack of instability and a very dry column below it will lead to
very low chances of rainfall through most of the night. Before the
higher clouds approach...optimal radiational cooling conditions
are likely to exist with a very dry boundary layer and calm winds.
As such...rapid fall offs in temperatures are expected this
evening...before the diurnal fall off ebbs a bit overnight. More
active weather looks to hold off until after tonight. Fries
Short term /6 am Saturday morning through Monday/...
shower and thunderstorm chances will increases this weekend as a series of shortwaves
move out of the Great Lakes region. Surface frontal placement undr
incrsg but more zonal flow will be critical for upper Ohio Valley severe
potential. At moment...the initial severe chance...albeit slight...resides
with passage of a potential mesoscale convective system or remnants late Saturday or early
By Sunday...a trailing...and more potent shortwave is prognosticated off the
Great Lakes. Incrsd deep layer shear and steepening middle level lapse
rates with that feature will be plenty sufficient for an array of
severe weather...but limitations arise in actual instability
parameters and boundary placement...especially in relation to outflow
reinforcement from the Saturday system.
At any rate...the Storm Prediction Center has highlighted the
region with these possibilities and local mention has been continued
in the hazardous weather outlook.
Long term /Monday night through Friday/...
the long term will feature an eastern Continental U.S. Upper trough persisting through
the period with below average temperatures. Surface ridging will build in under the trough by
middle weak...keeping only unmentionable slight chances for showers in the
forecast. The ridging is expd to weaken by lt weak with better chances for
Aviation /01z Saturday through Wednesday/...
mostly clear skies will give way to some middle and high level clouds
tonight...ultimately keeping fog development at Bay. VFR
conditions will prevail Sat...although some restrictions could
come as shower and thunderstorm chances will be increasing Sat
night into Sunday...just beyond the scope of the taf period.
Outlook.../Saturday night through Wednesday/...
low pressure will likely bring shower/thunderstorm restrictions
late Sat night and sun. Additional restrictions are possible Monday as
the associated coldfront crosses.