Scientific Forecaster Discussion
fxus61 kpbz 221722
Area forecast discussion
National Weather Service Pittsburgh PA
122 PM EDT sun Sep 22 2019
a cold front will bring shower chances to the region Monday. More
seasonable temperatures and mostly dry weather is expected through
the end of the week.
Near term /through tonight/...
dry and unseasonably warm weather will continue for the rest of the
daytime hours, with occasional afternoon gusts up to 20kts that will
mix out some surface moisture in the region.
The ridge will break down tonight as the upper level trough moves
over the Great Lakes. Clouds will slowly increase west to east
overnight as the trough pushes the upper level moisture plume into
the region, which should help mitigate morning River Valley fog
Short term /Monday through Wednesday night/...
a pre-frontal sfc trough will push the first band of showers through
the region during the morning hours Monday. Showers along this front
will generally dissipate as they move west as it outraces its upper
level support, with the main upper level trough remaining over the
western Great Lakes. Thunder is unlikely as well given this lack of
support and no progged instability.
The main cold front will move through the region later in the day as
the upper level trough swings east. A second line of showers will be
possible along this boundary, but the extent and intensity of this
new development will be dependent upon how quickly this pre- frontal
trough can exit east and the degree of heating that occurs ahead of
the front. The potential for heat recovery plus the cooling
temperature aloft may allow for enough instability for thunder, so
added a slight chance. However, it remains just as likely that the
morning trough/rain stabilize the area and showers struggle to even
develop as the actual cold front moves through.
Increasing sfc high pressure and cool northwest flow to zonal flow will
fill in behind the exiting trough starting Monday night. Outside of
a chance for lake enhanced showers developing north of I-80 Tuesday
afternoon within the northwest flow, this pattern will result in dry weather
and seasonable temperatures for the region.
Long term /Thursday through Saturday/...
a weak shortwave trough and its weak frontal boundary will clip the
region Thursday and provide shower chances. Thereafter, ridge
building will commence across the eastern U.S. Through the weekend as
a series of disturbances help deepens the trough over the western
U.S. This will result in mostly dry weather with well above normal
Aviation /17z Sunday through Thursday/...
VFR conditions will continue through the night in southwest flow
ahead of an approaching upper trough. Wind will gust to between 15
and 20 knots at times this afternoon before settling down this
evening. Low level wind shear will be possible overnight as 35 to 40
knot wind blows just above the boundary layer.
Restrictions will become more likely after 12z with the approach and
passage of a cold front. MVFR ceilings are expected just along and
behind the boundary, while visibility restrictions from showers will
be few and far between.
restrictions may continue through Monday afternoon, before drier air
and increasing surface pressure bring a return to VFR conditions by