Area Forecast Discussion
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FXUS61 KPBZ 301622 AAC

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
1222 PM EDT SAT JUL 30 2016

Periodic showers and storms will continue through the weekend until
high pressure brings the return of dry conditions for much of next


As of the early afternoon update time, prior analysis and
expectation for shower/storm development and propagation seem to
be working out fairly well. Rain rates in excess of an inch per
hour have been common, however flooding reports to this point have
been rather minor, even in urban areas. Thus, while a flood watch
was pondered, it seems spotty advisories for flooding will be
sufficient to handle the unfolding scenario at this point. The
previous discussion follows with the details...

A nearly moist adiabatic profile exists over the CWA as of the 12z
KPBZ raob with a freezing level up near 12.5 kft and thus warm
rain processes dominating the semi-unstable cloud layer. Steering
flow and shear over the area remains rather weak, thus storm
movement will be rather slow SW-NE through the day. That said, the
sounding PWAT of 1.76 inches is rather soggy, and the presence of
a backbuilding 250 hPa jet to the north of the CWA may become
problematic during the day. This places the CWA in the right
entrance region of said jet with a weak H5 wave approaching from
the west. As a result, SWerly propagation of cells is expected
during the day with resultant multiple waves of convection likely
to move NEward through the area as a result. This will yield the
threat of heavy rainfall possibly moving over similar corridors at
times during the day. Localized flooding will be possible in this
setup, and it has been included in the HWO as a result.

Deep moisture in place will keep clouds largely entrenched over
the area through the day. While morning lows were elevated
because of the clouds, they will not likely be a harbinger of a
warm afternoon. Clouds may well keep temperatures largely below
normal generally east of New Philadelphia, Ohio. Fries


Shower and storm chances will continue on Sunday as the upper
trough continues to transition east and the surface low associated
with the aforementioned boundary crosses across the north. Drier
air will finally begin to move in aloft on the backside of the
trough which will bring an end to shower/storm chances by Sunday
night. Maintained a dry forecast for Monday under continued dry
northwesterly flow, but there is an outside chance of afternoon
storms as latest model runs indicate a small jet streak developing
Monday afternoon and just enough low-level moisture remaining.
May need to include mention of showers/storms in future updates if
models show continuity with this feature.


Surface high pressure will build into the area from the western
Great Lakes Monday night into Tuesday. This will allow the area to
remain in cooler northerly flow even as subsidence builds. A dry
forecast will thus be maintained through mid-week.

Ridging at all levels of the atmosphere should thereafter increase
from mid-week onward as amplification of the pattern is evident on
basically all guidance over the upper Mississippi Valley and
northern Great Lakes during the second half of the week. This
ridge and resultant low level thermal ridge should start to flop
over toward our area by Friday, which at this point looks to be
the warmest day of the next week or so, when temperatures should
push again well above normal.


Heavy rain in showers and thunderstorms has been yielding
occasional LIFR/VLIFR conditions /ceiling and visibility/.
Coverage is shifting more toward the eastern terminals early this
afternoon, which is expected to lead to increasing cloud height as
modest mixing occurs. Showers and storms will develop again later
this afternoon, but coverage and impact to specific terminals is
uncertain, so only vicinity remarks were used at this time until
timing and impacts can be determined more confidently.

Broad upper troughing should maintain the potential for periodic
restrictions in showers and thunderstorms through Monday.





UPDATE...Fries/Kramar is the U.S. government's official web portal to all federal, state and local government web resources and services.