Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
721 PM EDT Wednesday Jul 30 2014
scattered showers and thunderstorms will diminish early tonight.
Temperatures will begin to moderate toward seasonal averages by
Near term /through Thursday/...
showers and embedded thunderstorms have developed across the
region ahead of a passing short wave this evening. Cape values are
rather small and instability profiles fairly skinny on skew-T
charts...however very low wet bulb zero heights due to an
impressive cold pool aloft and strong low level lapse rates have
made for a decent amount of pea sized hail reports. A few of these
cells did manage to attain vertical development to briefly produce
larger hail...however with the loss of diurnal instability...the
window for larger hail has likely already closed. Some nominal
clearing is likely behind this first wave through the latter half
of the evening. Fries
Another quick moving and weak upper impulse will cross the
eastern Great Lakes later tonight into early Thursday with slight
chance probability of precipitation from Pittsburgh north. Continued cool temperatures
with lows again in the 50s and highs in the 70s.
Short term /Thursday night through Saturday/...
by Friday upper level trough axis will begin to transition west as
a ridge builds in the western Atlantic. With developing southwest
flow aloft deeper moisture will begin to move north during the day
Friday into Saturday. Best rain chances should initially be along
the southeast ridges spreading west with time. Temperatures will
warm to near seasonal average for the start of the weekend.
Long term /Saturday night through Wednesday/...
deeper moisture will remain across the region Sunday but models
have not shown the best continuity in regards to timing the next
shortwave to pass through and help support activity so have opted
to leave chance probability of precipitation for Sunday. Dry conditions are forecast by
Monday as operational runs show the long wave pattern becoming
more zonal. Next front may arrive Wednesday.
Aviation /23z Wednesday through Monday/...
shower storm coverage will diminish this evening. Cloud cover will
be a bit tricky...as latest models showing weak cold air advection overnight.
Will keep a VFR forecast for cloud cover overnight...with a scattered-
broken coverage. Will include the mention of fog at zzv and mgw as
they should see less cloud cover. Will go with MVFR tempo LIFR at
zzv. In addition to the threat for fog...another shortwave will
swing through the north tonight which could bring showers back
into fkl and duj. Will keep in a tempo group for these ports for
Cool pool aloft will slowly drift northward Thursday morning which
will allow for any stratocu to decrease. VFR conditions on
Thursday with wind gusts to 15kts out of the west in the
Outlook.../Thursday night through Monday/...
no widespread rstrns expd.