Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
245 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/...
eastward retreating surface high under west-northwest flow aloft will keep the area dry
and through tonight. Shortwave in that flow will increases cloud cover and may
spawn some sprinkles in the peri dawn hours...but measurable precipitation
chance is minimal...and confined to the northern half of the County Warning
Area. Cool near term temperatures were forecast near sref means.
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 /19z Friday through Wednesday/...
dry surface high pressure will maintain VFR conds through tonight. A weak
disturbance will cross the region Sat. VFR SC/cumulus will increase...though
shower/thunderstorm chances appear too low for a taf mention at this time.
Outlook.../Saturday night through Wednesday/...
advancing low pressure will likely bring shower/thunderstorm rstrns lt Sat night and
sun. Rstrns are possible Monday as the low/S associated cold front crosses.