Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
312 am EDT Thursday Apr 2 2015
shower chances are expected to increase today through Friday night
as a cold front slowly tracks across the area.
Near term /until 6 PM this evening/...
clouds should quickly increase this morning as the next shortwave
and its associated cold front approaches. The first round of showers
are expected today in warm advection and with low level jet
development...and continued increasing probability of precipitation to likely from W-E.
Prognosticated instability is limited...but did maintain isolated thunder
mainly west of pit. Mixing should allow for some gusty southwest winds
by afternoon. With a quick onset of clouds and showers...high
temperatures should be held mainly in the 60s to near 70 using the
latest sref and lamp numbers.
Short term /6 PM this evening through Sunday/...
the cold front is prognosticated to drop S across the region tonight...
stalling out from SW Ohio into southern PA. Continued categorical
probability of precipitation for showers...and an isolated thunder mention for much of the
area as showalter indicies drop below zero with elevated
instability and a persistent low level jet.
A surface wave is prognosticated to track along the front from the MS
valley into the Ohio Valley Friday bringing additional showers to
the area. Isolated thunderstorms are possible S of pit again in
limited instability. The main upper trough axis is prognosticated to
cross the area late Friday night and early Saturday as the surface
low continues strengthening as it moves off the New England coast.
This should bring a rapid end to any precipitation...though a brief
period of snow showers is possible as it ends. Total rainfall
amounts of 1.25 to 2 inches are expected through Friday evening.
This will likely cause rises on area rivers...though significant
Hydro problems are not expected at this time. Preferred a blend of
the GFS/ECMWF...mainly due to their handling of the frontal
surface wave...and the more reasonable quantitative precipitation forecast numbers from the European model (ecmwf).
After building high pressure later Saturday...a weak shortwave is
prognosticated to brush areas north of I 80 with low precipitation chances on
Sunday. Above average temperatures Friday are expected to be replaced by
well below average readings Saturday...with some recovery for
Long term /Sunday night through Wednesday/...
next week temperatures are forecast to moderate to near...then
above the seasonal averages as a shortwave ridge develops over the
eastern half of the Continental U.S. In response to western states troughing.
Precipitation chances will rise as the week and trough progress.
The long term prognosis was primarily based on adjusted wpc
Aviation /07z Thursday through Monday/...
VFR is forecast until an approaching cold front generates showers
this afternoon. Low level wind shear is anticipated though as low
level jet intensifies above shallow inversion after daybreak. That
problem is likely to persist until mixing increases the surface wind
later in the day.
By tonight...condition degradation to widespread MVFR...and probably
eventual IFR...can be expected as rain becomes more widespread with
the encroaching front.
Outlook.../Friday through Monday/...
low pressure moving along the aforementioned frontal boundary will
main maintain restrictions into Saturday.