Area Forecast Discussion
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FXUS61 KPBZ 252215

Area Forecast Discussion
National Weather Service Pittsburgh PA
615 PM EDT Tue Apr 25 2017

Building high pressure will return dry, and very warm weather to
the Upper Ohio Region for Wednesday.


While the upper level low that has been parked to our south will
continue its painfully slow amble to the east, the jet streak to
its north should gradually fade this evening. As this occurs,
deeper lift in the highly curved right entrance region of this
jet will fade from western Pennsylvania. As a result, low level
easterly flow around the northern side of this low will have
increasing difficulty overcoming the downslope drying from
descending from the ridges. As such, light rain west of the
ridges will fade progressively over the next few hours. On
easterly facing ridges, this process will take longer until
deeper moisture departs to the east as well. After this occurs,
the remainder of the overnight will be dry with decreasing
cloudiness. Fries

Insolation with rising heights/warm advection in response to a
deepening plains trough will resume dry weather for Wednesday,
and drive temperature well above the averages. Expect readings
either side of the 80 F mark areawide.


Continued warm advection and mixing will support temperatures
well into the 80s on Thursday, but the aforementioned plains
trough is also progged to dig eastward and increase rain chances
as the day progresses.

While the low center is forecast to develop toward the James
Bay, models have been consistent in extending a negatively
tilted axis across the Upper Ohio region in the afternoon or
early eve. Should low/mid 80s temperature occur as projected
with a near 60 dewpoint, surface based instability would be
plenty sufficient to support a severe threat in the progged deep
layer shear field.

Mid level temperature in association with the fading ridge may
provide explosive-inhibition, but current thoughts are the
thermal trough may deepen the mid level lapse rates enough to be
problematic, especially in light of the developing wind
field/high shear environment. An additional point of interest:
NAM/GFS indicated mid level veer in association with a negative
tilt may support some splitting cells in addition to providing
an area of enhanced diffluence at peak heating. At any rate,
will begin a Hazardous Weather Outlook mention today with a
primary wind threat from short bowing segments supplemented with
a large hail threat.

Passage of this systems cold/occluding front will end precip
during the evening with Friday expected to remain mostly dry and
continued warm under a shortwave ridge.


Shortwaves ejecting from a Rockies-to-Plains trough will support
periodic rainfall chance for the weekend, timing and placement
of which remains questionable given expectations of amplified
flow/warm sectorization of the Upper Ohio Region as the Western
States system deepens and digs eastward. Very warm temperature
will continue until that system shunts a front across the region
early next week.


Ceilings will continue to bounce around this evening, with
localized MVFR conditions possible from HLG and east. Tonight,
remaining cloud cover will lower, but may begin to scatter out
as high pressure begins to build from the west. As skies begin
to clear west to east tonight, some terminals could see fog
development, especially towards daybreak.

Easterly winds at 10kts or less will gradually diminish

The next chance for general restrictions is expected with late
week low pressure.




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