Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
949 am EDT Monday Aug 3 2015
shower and thunderstorm development will accompany a cold frontal
passage later today.
Near term /through tonight/...
only changes needed for the middle morning update were adjustments to
morning probability of precipitation based on the latest radar and high res trends.
focus today will be on a cold front that will slide across the
region this afternoon and evening. Expect showers and thunderstorms
to fire in advance and along that front. Models continue to
struggle with the amount of instability the atmosphere will have
to work with...although there is good model agreement for modest
wind shear...which may help to organize storms should sufficient
updraft strength development.
Only limiting factors include residual cloud cover blanketing the
region this morning and the timing of upper shortwave
support...which has not been consistent run to run and model to
model. Bottom line is that the Storm Prediction Center slight risk prognosis looks
reasonable for now with the primary threat coming from wind gusts.
Short term /Tuesday through Wednesday/...
showers and thunderstorms will fade this evening as the front
finally slides across the I 70 corridor. Lingering showers are
thus possible across the southern counties into the overnight
Tuesday looks to be a dry day with broad high pressure building
over the upper Ohio Valley. A weak shortwave trough could bring a
shower to the north late in the day...but moisture will be
Most of Wednesday day should be dry. Another weak front will cross
the area late in the day...which could spark a few scattered
showers. At this point...confidence is low with how much rain this
feature will be able to produce as moisture and upper level
support are sparse.
Temperatures will remain around seasonal norms through the
Long term /Wednesday night through Sunday/...
there is good agreement in the long term forecast as an upper
trough remains parked over the eastern US. Several shortwaves
moving through the upper flow will maintain the chance for
showers and thunderstorms through the period...with overall better
consensus between the GFS and European model (ecmwf) than in the previous days
runs. With the trough prognosticated to deepen by next weekend...expect
temperatures to trend a few degrees cooler than seasonal averages
in northerly flow.
Aviation /14z Monday through Friday/...
VFR will dominate until convection develops with the advance of
the cold front toward the region this afternoon. Showers and storms
will taper off tonight as the front slides southward...although
restriction potential may linger for southern ports as boundary
layer moisture remains pooled in vicinity of...and just north of
the front into the morning.
And degraded conditions will rapidly improve on Tuesday with
building high pressure.
Outlook...Tuesday night through Friday...
the next chance for restrictions is expected with a Thursday