Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
141 am EDT Wednesday Aug 20 2014
a series of disturbances will keep occasional shower and
thunderstorm chances in the forecast through the rest of the week.
Near term /until 6 am this morning/...
the quiet night we have seen to this point will be unlikely to
last. A system currently traversing Northern Ohio is already
advancing on the western fringes of the County Warning Area late this evening...
spreading showers and thunderstorms right to the western doorstep
of the area. While they were quite strong earlier...radar
indications from kcle indicate they are already gusting out over
metropolitan Cleveland. As such...the cold pools under the storms
are now outrunning the updrafts...with a weakening trend in echoes
likely to follow shortly. While weakening is imminent...given
that the middle-level wave does manage to pass through the entire
region through Wednesday morning...likely probability of precipitation were retained for
The only other change to the forecast for the rest of the night
was to bump up lows a bit...particularly in Ohio. With dewpoints
there running in the lower 70s and rain impending...a lowering of
dewpoints is unlikely...which would be required to reach our
previously forecast lows. Additional convection-related cloud
cover will add to the problems with temperatures really falling
very much tonight. As such...lower 70s seem most likely in most of
our Ohio areas. Fries
Short term /6 am this morning through Friday/...
showers and thunderstorms will continue into Wednesday until the upper trough begins to
shift east of the area by evening. With the best upper spprt exiting in
the afternoon...and unimpressive shear...organized severe weather is not expd
at this time.
A surface boundary is then prognosticated to set up from surface low pressure over the upper
Midwest...southeastward into the Ohio Valley region. This will become the focus for
showers/thunderstorms Thursday through Friday. The best upper spprt...shear and instability is
prognosticated for Thursday resulting in at least some threat for severe weather
mainly S and west of pit in vicinity of the boundary. With rather high
uncertainty in the specific details will leave mention out of severe weather potential statement
for now. Little movement to the boundary is expd by Friday as the upper flow
turns northwest and becomes oriented with the boundary.
Temperatures will remain near or a little above the seasonal avgs.
Long term /Friday night through Tuesday/...
little change in the forecast is expected. This will mean a
continuation of shower and storm chances dependent on timing and
location of any upper level disturbances through Erly next week.
Upper ridging is prognosticated by Tuesday. Temperatures should remain near or a
few degrees above average.
Aviation /06z Wednesday through Sunday/...
showers/storms have lost a little bit of punch but continue to
work their way across the area. Outflow boundary out ahead of rain
is producing a 20-30 knot gust as it moves through...and have
tried to handle this for the next couple of hours. MVFR/spotty IFR
can be expected with this rain batch as it accompanies a
shortwave. Kept vcsh behind the main batch with redevelopment
A brief break in rainfall is possible between 12z and 16z or so
later this morning. Then...diurnal instability buildup will allow
rain showers/thunderstorms and rain to fire this afternoon. Kept thunderstorms in the vicinity mention as it is still
difficult to pinpoint location and timing...although brief IFR
restrictions are possible anywhere. Activity starts to calm down a
bit after sunset.
Outlook.../Wednesday night through Sunday/...
several crossing disturbances will cause periodic restrictions
into the weekend.