Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
759 PM EDT Thursday Jul 31 2014
temperatures will move to near average with daily chances for
showers and thunderstorms Friday through Sunday. Dry and mild
conditions to return by the beginning of next week.
Near term /through Friday/...
boundary layer stabilization should commence quickly with sunset.
This should eviscerate incipient updraft formation...yielding a
rather terse ending to isolated shower activity across the upper
Ohio Valley. A drier column aloft should allow for mostly clear
skies through the majority of the night except for western
wildfire smoke in the highest levels...which should make
temperatures poised for another plunge into sub-average
The forecast for overnight was updated to limit probability of precipitation this evening
and trend back the development of showers from the south toward
Friday morning. Fries
Previous discussion for Friday follows...after patchy morning fog
expect clouds to be on the increase Friday as moisture streams up
the west slopes of the Appalachians as flow becomes more
southwesterly aloft. Chance probability of precipitation for showers and scattered
thunderstorms becoming likely in the southeast ridges closest to
best deep moisture. Temperatures approaching seasonal norms.
Short term /Friday night through Sunday/...
southwest upper flow will continue with deep moisture
overspreading the region as weak trough axis shifts west while a
ridge builds into the western Atlantic. Will be tough to time any
significant upper impulse so have gone with a broad brush for
chance shower probability of precipitation with higher probability of precipitation in the ridges. A diurnal
trend for thunderstorm chances with afternoon heating. Little
change to temperatures to average a bit below normal.
Long term /Sunday night through Thursday/...
mainly dry and mild conditions can be expected through the first
half of the week as the long wave pattern becomes more zonal and dry
west/northwest flow sets up across the region. Operational models
vary greatly on the idea of showers/thunderstorms returning by
midweek so have included a slight chance on Wednesday...increasing
on Thursday based on ensemble guidance.
Aviation /00z Friday through Tuesday/...
VFR conditions will prevail until some MVFR fog develops overnight
toward morning. An increase in southwesterly moisture and
instability should result in some showers scattered about the
region by Friday afternoon.
Outlook.../Friday night through Tuesday/...
a low pressure system over the weekend could bring restrictions.