Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
226 am EDT Wednesday Sep 17 2014
dry and seasonable cool conditions can be expected into Friday.
Near term /through today/...
Low level cloud coverage that has developed over the past couple
hours has limited temperature falls overnight...while latest
guidance gives indication that scattered to broken cloud coverage
between 3-5kft should persist until after sunrise. With
that...still expect a fair amount of fog development as dewpoint
depressions are minimal but widespread dense fog is not likely and
advisories will not be needed. Scattered shallow cumulus will
develop tomorrow as there is enough moisture trapped under a
strong subsidence inversion at 5kft. With high pressure building
in and limited mixing aloft...temperatures will remain slightly
below normal. Tomorrow nights minimum temperatures will be similar
to those observed tonight and while there will be patches of fog
that develop...the extent will be less than what has recently been
observed during the mornings.
Short term /tonight through Friday night/...
a shortwave will push a reinforcing cold front across New York
state Thursday. This will bring more clouds daytime Thursday but
not enough moisture to put in any probability of precipitation. Otherwise cool high
pressure will dominate with below normal temperatures.
Long term /Saturday through Tuesday/...
a warm up expected for the early weekend as the surface high shifts
well east of the area and upper level flow becomes more zonal.
Temperatures will...at least temporarily...return to near average Sat/sun
ahead of the next system. The best chance of precipitation over
the next 7 days will come with an elongated trough and associated cold
front sun with possible showers with cold air aloft Monday. Cool
high pressure Tuesday.
Aviation /06z Wednesday through Sunday/...
areas of scattered to broken cloud coverage that has developed
will limit overall fog formation overnight in
general...however...IFR fog will still be possible at terminals by
daybreak this morning. Particularly in the valleys and over areas
where clouds were limited overnight. Fog will burn off by
14-15z...leaving scattered shallow cumulus around 5kft above ground level.
Outlook...Wednesday through Sunday...
outside of the possibility of valley fog one or two mornings...VFR
conditions are expected through the week.