Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
841 PM EDT Tuesday may 26 2015
warm and humid conditions will persist through the week...with
periodic shower and thunderstorm chances.
Near term /until 6 am Wednesday morning/...
with unimpressive instability...thunderstorm development has been
fairly nominal...with no reports of anything even approaching
severe. As the night ensues...and instability remained modest at
best...development will likely be fueled by an increase in middle-
level relative humidity values and increased shear. This is unlikely to result in
much thunderstorm development...however some heavier showers will
be likely to cross the area overnight as a short wave pushes
through the area. More organized shear looks to hold back for the
main long wave trough crossing on Wednesday.
Increasing clouds across the area as convective activity
encroaches will likely keep a floor under temperatures tonight.
Lows will stay largely well into the 60s. Fries
Short term /6 am Wednesday morning through Friday night/...
the shortwave is prognosticated to exit the region Wednesday morning with
decreasing precipitation chances. Another shortwave is prognosticated to cross
the area Wednesday evening with an increase in shower and
thunderstorm chances...though marginal shear values should help
limit the severe potential.
Ridging late Thursday and Friday behind the departing shortwave
should allow for mainly dry weather. Above average temperatures
are expected to continue through the period.
Long term /Saturday through Tuesday/...
various long range solutions agree on stubborn boundary laid
across the forecast area through the weekend. Therefore chance
probability of precipitation were preserved with the support of a series of upper level
disturbances across the upper Ohio Valley. GFS and European model (ecmwf) differ
over the outcome of an approaching trough from the Midwest in
terms of magnitude...position...and timing. Therefore persistence
was heavily used in the latter half of the period and low chance
probability of precipitation were introduced.
Aviation /01z Wednesday through Sunday/...
restriction potential...mainly MVFR...is expected to increase late
tonight as a shortwave supports more showers...and lower clouds as
dawn approaches. In the meantime...general VFR through the evening
with temporary restrictions in showers and isolated thunderstorms.
MVFR restrictions are expected for a portion of Wednesday
morning...but clouds will eventually lift and return to VFR.
Outlook.../Wednesday night through Sunday/...
overall improvement is indicated as precipitation chances decline
through Friday. However...precip...and restriction chances will
again increase with an encroacing frontal system this weekend.