Area Forecast Discussion
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FXUS61 KPBZ 241241

Area Forecast Discussion
National Weather Service Pittsburgh PA
841 AM EDT Wed May 24 2017

Unsettled weather will return for the remainder of the week as
an upper-level disturbance moves slowly across the Ohio Valley.


As a deep upper low slowly migrates toward the western Great
Lakes today, a couple of weak short waves troughs embedded in
southwesterly flow aloft are set to transit the area. This fact
combined with a rather haphazard low/mid-level deformation field
have allowed for scattered showers to continue to develop across
the area early this morning, and it is expected this trend will
continue through much of the day. Between these weak waves,
however, episodic thinning of the clouds will allow for breaks
of sun at times during the day today.

More coherent shower activity will start to encroach on the area
late in the day as the upper low over the western Great Lakes
starts to migrate eastward. Even still, due to abundant layer
moisture ahead of this system, clouds will be common through the
day with diurnal ranges looking rather subdued as a result.


The upper low will gradually first dig into the mid-Mississippi
Valley before slowly ejecting toward our area. This will all
take through Thursday to occur. As it does so, lapse rates will
steadily increase due to mid-level cooling even as boundary
layer temperature remain rather subdued due to rain cooling and
abundant cloud cover. As such, chances of thunderstorms and
showers will remain in the forecast with generally below normal

By Friday, the upper low will have shifted toward New England
with northwesterly flow in control and a bit of drier air
working into the region. This will be rather short-lived,
however, as the H5 ridge axis looks to shift through the area by
Saturday with broad southwesterly flow becoming established.
This will allow for more humid and warmer conditions to arrive
for the weekend. However, it will also bring in chances of
showers and thunderstorms yet again. In fact, some solutions
have featured an MCS traversing the region on Saturday. Stay
tuned on that.


The pattern going into next week looks to continue to amplify as
an upper low again drops into the Mississippi Valley with a
downstream ridge popping up rapidly along the eastern seaboard.
Unfortunately for us, we will be stuck between these two areas
with broad southwesterly flow remaining in place and thus
abundant moisture streaming toward the area. As a result, shower
chances will remain with temperatures not too far from normal.


VFR conditions are expected to deteriorate through midday as
low level moisture increases with a crossing shortwave.
Maintained a VCSH mention in the TAF with sct shower coverage
expected. Improvement back to VFR is expected by late
morning/early afternoon before deterioration back to MVFR in
showers late in the day with approaching low pressure.

Increasing SE winds are expected today with an increasing
pressure gradient, with a few 20-25kt gusts especially for the
higher terrain ports.

Restrictions are likely through Thu night, and again over the
weekend, with low pressure.




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