Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
459 am EDT Thursday Sep 3 2015
warm and humid conditions will continue into the weekend with a
chance for showers and thunderstorms through Friday.
Near term /until 6 PM this evening/...
a series of shortwaves...in the northwest flow aloft...will keep
in shower and storm chances throughout the day. Atmosphere will
destabilize today with forecast soundings indicating a k index in
the middle to upper 30s and mu convective available potential energy pushing over 1500j/kg. With
little atmospheric flow in the current regime...shear values are
not impressive...leading ME to believe that any convection that
does develop will have a difficult time sustaining updrafts thus
leading to a short life span. The weak flow also means that
storms will be slow moving. Precipitable waters remain near 1.5 inches...so a
heavy downpour is possible. The activity will gradually end this
evening with the loss of daytime heating.
Short term /6 PM this evening through Saturday/...
slight to low chance for diurnal convection continues on
Friday...mainly for areas south of pit. Temperatures will average
5 to 10 degrees above normal.
Increasing upper level heights on Saturday as ridge expands
eastward. Large surface high will drift westward across PA under
strengthening ridge. Don't expect any diurnal activity
Saturday due to the increase in large scale subsidence.
Muggy and warm conditions will continue.
Long term /Saturday night through Wednesday/...
the strong middle/upper ridge is prognosticated to rebuild through the long
term period. Relief from the dry and warm conditions may come
with cold front later next week.
Aviation /09z Thursday through Monday/...
MVFR fog is becoming more common early this morning...with local
IFR/LIFR conditions likely to persist around kfkl and kduj through
sunrise. Fog should again quickly mix out after sunrise...allowing
for VFR conditions through the day at all sites. Winds will again
be exceedingly light as steering flow is very weak.
Additionally...an isolated shower or thunderstorm will be possible
by afternoon as a weak middle-level disturbance slowly translates to
the southeast toward the area...however coverage will be isolated
and timing far from certain...so inclusion in the coded forecasts
is precluded. Fries
Outlook...Thursday night through Monday...
brief restrictions are anticipated with peri-dawn fog.