Scientific Forecaster Discussion
fxus61 kpbz 251304
Area forecast discussion
National Weather Service Pittsburgh PA
904 am EDT sun Jun 25 2017
upper low pressure will maintain cooler temperature and a periodic
shower chance for the first half of the week.
Near term /until 6 PM this evening/...
mid-level temperatures look to fall off another 4-5c by this
afternoon as a mid-level short wave crosses the area concurrent
with peak heating. A fairly vigorous upper jet streak will be
transiting likewise, and the combination of DPVA, right entrance
region upper divergence, and increasing lapse rates will yield a
good combination of forcing for ascent and instability. This
will at the very least generate a marked uptick in cumulus
development along a boundary that moves through this afternoon.
The mitigating factor will likely be fairly lean layer moisture.
However, given the instability profiles, 12z sounding convective
temperature of 71f that should easily be eclipsed, and hi-res
model depictions, isolated showers with the passing short wave
seem like a fairly good bet and were added to the forecast for
most areas. Furthermore, model soundings suggest wet bulb zero
heights falling off toward 5 kft, which would favor some small
hail development in the more vigorous updrafts.
With cold advection underway through the day through the column,
high temperatures will be largely restricted to several degrees
below normal. Fries
Short term /6 PM this evening through Tuesday/...
a series of shortwaves are projected to cross the region during
the short term period. Improved dynamics and an improved, but
still limited moisture tap support better precip probability for
the period. Temperatures under the persistent troughing remain
progged about 10 degrees under the averages.
Long term /Tuesday night through Saturday/...
the long term period will feature moderating temperature as flow
aloft flattens/ridges in response to a trough digging out of
western Canada. Humidity and warmth will enhance with the progress
of that trough over the plains/Midwest, and precip chances
escalate as the system erodes the eastern ridge by the weekend.
Aviation /13z Sunday through Thursday/...
only some minor restrictions with patchy fog this morning,
mainly for fkl/duj through sunrise. Otherwise, VFR conditions
will continue through the period despite a broad upper-level
trough. Diurnal cumulus will return again today, along with
scattered showers, primarily north of Pittsburgh. Winds will
generally remain westerly increasing to near 10kts during the
day, with gusts 15-20kts.
chance for restrictions will come with afternoon convection on
Monday as an upper trough axis moves through the region.