Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
1114 am EDT Thursday Oct 30 2014
weak high pressure will build in today. Low pressure will cross
the region Friday and Saturday with unsettled weather.
Near term /through tonight/...
lingering stratocu behind an exiting shortwave will continue across the area
into the afternoon with cool air aloft. Some dcr in clouds is expd toward
evening as weak subsidence increases under building high pressure.
Clouds will begin to increase again overnight ahead of the next approaching shortwave.
Temperatures should average a little below seasonal avgs.
Short term /Friday through Saturday/...
a deepening upper trough and its associated surface low will advance across the
Great Lakes Friday with increasing shower chances through the day. The deep upper trough will
remain across the eastern Continental U.S. Sat with a moisture swath and Omega across
much of the region.
Colder air is expd to begin to move in behind the initial surface low
as north-NE flow develops Friday night into Sat. Critical thicknesses and
sounding profiles indicate this could allow for some snow to mix in
with rain showers at times...but a warm boundary layer should limit the
snow potential and prevent any accums outside of the ridges southeast of
pit. In the ridges...experimental a gradual change over to mainly snow Sat in the
highest elevations. Generally experimental a couple of inches of snow in the
highest terrain in grassy areas before the precipitation begins to dmnsh
Sat night. The upslope component is limited with north-NE flow...and
moisture begins to dmnsh by the time northwest flow develops.
Below seasonal average temperatures are expd into the weekend.
Long term /Saturday night through Wednesday/...
used HPC guidance for this period which was based on gefs/ecens means.
A cold Sunday night will be followed by moderating temperatures...with
readings close to seasonal by Tuesday as a flat upper ridge is
forecast to move through. Another...much more shallow trough is
projected for a middle week...with Promise of an unsettled end to the
Aviation /15z Thursday through Monday/...
residual stratocu blanket will continue to plague most ports this
afternoon with MVFR to low end VFR...but improvement is anticipated
lt today as cold advection ceases and as subsidence increases undr a shortwave
Light surface wind will veer to the SW and S late tonight as upstream shortwave
advns...but genl condition deterioration is not anticipated with
that system until aftr daybreak Friday.
Outlook.../Friday night through Monday/...
widespread restrictions are expected on Friday as deepening low
pressure shunts a broad moisture swath over the upper Ohio region. Ensuing
upsloping cold advection will then maintain shower and stratocu potential
until surface high strengthens on Sunday.