Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
742 PM EDT Thursday Sep 18 2014
the next rain chance will come with a Sunday cold front.
Near term /through Friday/...
surface high pressure undr cool northwest flow aloft will maintain dry and cool conditions
through Friday. For tonight...no frost problems are indicated with
dewpoints in the 40s and models indicating cloud development with an inverted
trough alng the ridges.
Short term /Friday night through Sunday/...
model consensus favors a late Saturday night into early Sunday
afternoon timing for next cold front passage. Given that the model
spread with the system is fairly narrow...the NAM being the only
slow outlying model...confidence in probability of precipitation is sufficiently high to
include likely numbers across northern counties of the County Warning
Area...where the btr precipitation spprtg dynamics are prognosticated.
Models generate a few hundred j/kg of cape ahead of the frontal
boundary on Sunday. This combined with 30 kts of 0-6 km shear may
be enough to allow for a few thunderstorms to develop along the
front...so a slight thunderstorm chance was added to the forecast.
Dry advection and subsidence should quickly end the potential for rain by
Pre-frontal mixing and warm advection will drive Saturday temperatures
about 5 degrees above the avgs. Cooler air will infiltrate on Sunday
afternoon and remain into middle week.
Long term /Sunday night through Thursday/...
overall dry and cool pattern is expected for the remainder of the
long term period.
Aviation /00z Friday through Tuesday/...
VFR with building high pressure is expected to be blemished only by some
peridawn fog. Surface wind will remain light...but is projected to become
east or southeast Friday afternoon.
Outlook...Friday night through Tuesday...
genl restrictions are likely with a Sunday cold front.