Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
321 PM EDT Wed Aug 31 2016
a frontal boundary will bring showers and thunderstorms through
tonight. High pressure returns Thursday, with a cool and dry
pattern continuing through Friday.
Near term /through Thursday/...
showers and a few embedded thunderstorms are following a cold
frontal boundary into the northern County Warning Area counties. More scattered
showers and storms are developing in the more unstable air mass to
our west. Morning cloud cover kept a lid on cape increases
earlier, and this minimum is still seen on mesoanalysis maps. With
this lack of instability and with soundings becoming more moist
adiabatic, severe thunderstorms are not seen as much of a threat.
The main issue will be the possibility of high rainfall rates and
isolated flooding issues. Pwats increase into the 1.8-1.9 range
this evening, and there is some potential for training storms. Did
not have enough confidence for a Flash Flood Watch, but did update
the hwo, mentioning isolated flooding. Coverage should begin to
decrease after 00z as some upper support is lost, and the hrrr has
been consistent in showing this trend.
Showers will linger south of Pittsburgh overnight, with some
postfrontal stratus as well. By 12z, only the southeast ridges
should see a few isolated showers remaining. High pressure builds
in on Thursday, with troughing in the upper levels. The stratus
will break during the morning, and plenty of sunshine is expected
during the afternoon. High temperatures will come in below normal.
Short term /Thursday night through Saturday night/...
surface high pressure will continue to build into the region,
with mostly clear skies across the region. Thursday night through
Friday night will be the coolest period through the seven day
forecast, especially due to northerly winds. Highs on Friday will
be similar to thursday's values, while lows will be in the 50s in
most locations both nights.
Perhaps the biggest change to the forecast deals with the track
of Tropical Storm Hermine over the weekend. Hermine is forecast
to track from the Gulf of Mexico, pass over Florida, then move
into the Atlantic Ocean. All 12z models now show Hermine tracking
closer to the Atlantic coastline than previous model runs. As a
result, have added chance pops across eastern counties Saturday
into Saturday night. Also bumped up sky cover across most of the
forecast area, although at this point, wind gusts do not appear to
be more than 10-15 mph anywhere in the County Warning Area.
Long term /Sunday through Wednesday/...
although there will be a slight chance of rain across eastern
counties Sunday morning, once Hermine GOES east, the pattern will
become quiet again as an upper level ridge builds across the
eastern United States Monday and Tuesday. As the ridge breaks down
on Wednesday, the chance for rain will increase. Temperatures will
be on the rise once again through the first half of the week, with
temperatures approaching 90 degrees by Wednesday.
Aviation /19z Wednesday through Monday/...
scattered showers and thunderstorms are expected with a frontal
boundary. Have timed the best chances of heavier showers via MVFR
tempo groups as the front sinks across. A brief period of IFR is
possible in any storm with heavy downpours. Precipitation will
decrease in coverage after 00z. MVFR stratus is expected to linger
behind the front at most terminals. The stratus will break once
mixing commences Thursday morning, with VFR conditions forecast
Outlook /Thursday through Monday/...
VFR conditions under high pressure through the weekend.