Area Forecast Discussion
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FXUS61 KPBZ 232000

Area Forecast Discussion
National Weather Service Pittsburgh PA
400 PM EDT Thu May 23 2019

Severe storms are expected later this evening with the passing of a
cold front. Quieter weather is expected Friday as high pressure
builds over the Great Lakes.


With 4pm update, made minor tweaks to hourly temperature and dewpoint
grids. Still no radar echoes in the vicinity as the area is in the
lull between the rain that moved through this morning and the
thunderstorms that are expected to develop over the next few hours.
Previous discussion follows.

As we move into the late afternoon/early evening, a flattened upper-
level ridge is expected to tilt and northwest flow will dominate. Due
to a more northerly flow, cooling is expected to increase aloft.
This will create a more unstable environment across our region, Hi-
Res models suggest 2500-3000 J/kg by this late afternoon. Skies are
currently clearing in portions of the Ohio River Valley as subsidence
takes over between the pre-frontal trough and an approaching cold
front. These clearing skies will help with daytime heating and an
increase of low level instability.

Between 4 to 6pm a cold front will push over Lake Erie and move
southeast. Along with the sufficient instability from the surface to
the upper levels, high deep layer wind shear is present as a upper
jet passes over the Great Lakes. Severe storms are expected to fire
up along or near the boundary. Some storms have the capability to
produce damaging winds, hail, and/or isolated tornadoes this

Showers and thunderstorms are expected to dissolve once the cold
front passes. Skies are expected to clear and quieter conditions will
prevail overnight as high pressure builds to our west.


Height rises and a surface high will keep Friday dry. Northwest flow
will keep temperatures near the climatological average.

As our region sits downstream of a building upper level ridge, cold
air will move in aloft and instability will increase throughout the
day Friday. As an weak upper-level tough embedded in the upper-level
ridge moves in Saturday afternoon, a chance for severe storms
returns. Mid and upper level wind shear on model sounds display
40-50kt winds that could cause damaging winds.


The long term will be dominated by the strength and placement of the
Eastern CONUS ridge. The area will lie on the northern periphery of
said ridge, meaning the warm and active pattern will continue.
Chances of showers and storms will continue throughout this period
as weak upper-level troughs quickly pass our CWA.


After a brief break in the weather, instability will increase again
after several hours of sunshine and increased moisture advection
ahead of a cold front. Storms are expected to fire again late
afternoon and into the evening. Severe weather is possible with large
hail, damaging winds, and possible tornados.

Periodic restrictions are possible through the weekend as
disturbances round the upper level ridge.




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