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Select Your Area NWS Weather Forecast Office
NWS Area Weather Forecast Discussion
County Warning Area [CWA]: PBZ
Regional NWS Weather Office: Pittsburgh, PA

000
FXUS61 KPBZ 220755
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
355 AM EDT Wed May 22 2019

.SYNOPSIS...
Rain chances return late today as a weak upper level wave moves
through. A better chance for showers and storms on Thursday with a
crossing cold front.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Most of the day looks dry and warm with a building ridge aloft and
surface high pressure. A weak upper level wave will hit strong
resistance late this afternoon and evening as it bangs into ongoing
height rises over the region. Have pulled back on PoPs late this
afternoon/evening and kept thunder more isolated. Increased
subsidence from the aforementioned ridge, and a capped atmosphere due
to warm advection, will make it tough for any convection to develop.
Forecast soundings show little instability, with most of that over
Ohio. What upper level support does exist, will likely be used trying
to halt the northward expansion of the Eastern CONUS ridge.
Additionally, the area may not reach convective temperatures and
surface dewpoints may be held down due to a more southeasterly flow.

A nice rebound in temperatures today.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
Minor height falls are expected overnight and any showers that do
develop will end quickly with a decrease in large scale ascension and
deep moisture.

A better chance for convection will arrive on Thursday as a cold
front approaches and slowly moves through the area. Seeing some
timing and intensity differences between the models, mostly centered
around the strength and timing of a shortwave trough. Have focused
higher PoPs in the afternoon and evening as well as convection, using
the cold front as a guide. Atmosphere does destabilize Thursday
ahead of the front, but temperatures aloft remain rather warm until
shortwave energy crosses. Forecast soundings are indicating the cap
will hold until the cooler air aloft arrives. Much of the upper
level energy will initially be used to flatten the ridge, but there
will be enough left to drive the front through my CWA. There remain
minor model differences in atmospheric destabilization Thursday
afternoon, but all are still showing rather impressive buoyancy.
Low-level lapse rates will increase as will wind shear values, which
may lead to strong to severe storms ahead of the cold front. Pre-
frontal cloud cover and showers will play a role, as the lack of
full sun could prevent convective temps from being reached. There are
some indications that all of the necessary ingredients will be more
readily available over the southern half of the area late Thursday.
If this holds, areas from PIT-south and east could be the focus for
severe convection.

Front may get held up a bit Thursday evening as the shortwave trough
energy evaporates and height falls slow. This will need to be
monitored in future forecasts to allow for correct timing of the end
of showers/storms over the south. All activity will end late
Thursday night.

Rapid height rises are expected Friday as is another push of warm
air. Will leave Friday dry due to the increase in subsidence, the
development of a cap, thanks to the warm temperatures aloft, and
stable lower levels.

Temperatures Friday should be close to late May normals.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The strength and position of the eastern ridge will be the driving
factor for the long term weather. Ensemble data is in good agreement
that the area will lie in the zonal flow just on the northern flank
of the ridge. Precipitation will be driven by shortwave energy that
moves through the upper flow and if this energy is able to push any
surface boundaries through. It is possible that a weekend cold front
could get held up near or over the area as it will be unable to
move southward due to the strong ridge over the southeastern US. If
this comes to fruition, the extended would likely portray an
unsettled forecast, particularly by the end of the weekend and into
early next week.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions will prevail through the TAF period. Wind will veer SE
after dawn today as high pressure gets displaced to the east. Gusts
near or in excess of 20 knots will be possible through the day.

A weak disturbance will move through late in the afternoon, possibly
bringing a few showers and even a tstorm to the region. However,
confidence is quite low so have kept out of TAF package with the
exception of ZZV.

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

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...None.
PA...None.
WV...None.

&&

$$

Forecast Discussion from: NOAA-NWS Script developed by: El Dorado Weather