FXUS61 KPBZ 210515 AAC
Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
115 AM EDT Fri Jul 21 2017
Relatively quiet today, a shower or storm is possible over the
southern half of the area. More activity expected this weekend,
perhaps with more strong storms and heavy rain Saturday and
.NEAR TERM /THROUGH TODAY/...
Only change to the overnight period is the eventual removal of
Pops from the Thursday evening convection. Then introducing
slight chance to low chance PoPs over the south toward dawn.
Will keep low chance to slight chance PoPs across the southern
counties today, as whatever is left of the weak boundary gets
hung up over Central West Virginia. A weak upper level wave is
expected to dive southward toward the boundary this afternoon.
Very warm temperatures aloft will provide a cap, thus the low
chance PoPs. Rest of the area looks warm, muggy and dry.
.SHORT TERM /TONIGHT THROUGH SUNDAY/...
Model differences arise again this weekend with the timing and
strength of a shortwave that will dive through the region in
the northwest flow aloft. For now will lean away from the very
energetic NAM solution for Saturday/Saturday night. Because of
these large differences in the models, have low confidence at
this point for most of the weekend. The next major shortwave
trough is expected to bring showers and storms to the area
sometime on Saturday and continue into Saturday night. In
addition to the upper level wave, a surface cold front will
drift through the area Saturday night. By favoring a solution
closer to the GFS, have slowed likely PoPs on Saturday, focusing
them more toward the afternoon hours. There will be many
factors at play on Saturday, which will determine the strength
of the convection. Amount of sunshine, very warm air aloft, timing
of wave, timing of surface front and the possibility of surface
reflection developing along the front which will impact the
speed at which the boundary moves through. Hopefully, a model
consensus will develop over the next few runs.
Differences continue into Sunday, as does the low confidence in
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A general Great Lakes/northeast U.S. trough will be carved out
by Monday, with this pattern holding into mid-week. Temperatures
will fall back to near or just below normal during this period.
After lingering showers, Tuesday and Wednesday appear dry with
high pressure settling over the region. A return to northwest
flow may herald increasing rain chances Thursday.
.AVIATION /05Z FRIDAY THROUGH TUESDAY/...
Vis restrictions overnight due to fog development will clear
between 12 and 13z this morning. Otherwise VFR conditions
expected through the day. Slight chance of TSRA at KZZV but not
enough for inclusion in the TAF at this time.
Additional rounds of storms are expected through the weekend,
and morning fog is possible as well.
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