Area Forecast Discussion
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FXUS61 KPBZ 250342 AAA

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
1142 PM EDT Fri May 24 2019

Rain chances will increase over the next 24 hours as returning warm
air and moisture interact with crossing upper disturbances.


Quiet weather expected overnight with strong ridging in place.
A weak shortwave riding the northern periphery of the ridge may be
able to spawn a shower or two for areas north of I-80 along the warm
front as it moves through, though confidence is rather low given
upper lift will be displaced farther north.

With increasing cloud coverage and southwesterly flow overnight lows
will be relatively mild.


The ern CONUS upper ridge will flatten on Saturday and instability
will be on the increase as temperatures warm back into the 80s and
dewpoints return to the mid/upper 60s. This along with increasing
shear as a mid-level wave to the north crosses Ontario flattens the
ridge will increase thunderstorm chances once again. Mid-level
temperatures should inhibit convection initially...but later in the
day surface temperatures should reach convective thresholds and upper
support will be increasing.

Shear profiles are progged to be well balanced with forecast mean
sfc and ML CAPE values and there will be a good chance convection
becomes organized later the day and potentially persist into the
evening. SPC has maintained a slight risk over the northern 2/3rds of
the CWA and marginal to the south...which seems reasonable given
forecast soundings which show potential for damaging winds, large
hail, and tornados. Models suggest more scattered convection early
on followed by an MCS being maintained and dropping out of the north
in the evening. Have maintained mention of the severe weather threat
in the HWO.

Models are hinting at a weak boundary stalling over the northern
half of the region Sunday morning. By this time, the flow aloft will
be zonal and another wave of energy will sprint toward the area
Sunday afternoon. A surface wave will develop over the upper Mid-West
and move eastward along the stalled boundary late Sunday. The
aforementioned upper level wave will work to maintain decreasing
500mb heights, and the stalled front will be slowly directed toward
Northern WV Sunday evening. This movement will force the midwest
surface low to drift southward as well. This setup would promote a
period of widespread showers and possibly thunderstorms late Sunday
that will drift southward Sunday evening. Training/backbuilding
storms will also be with all things combined flooding
will be a concern Sunday into Monday morning.


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.


Some isolated rain showers have developed this evening, but coverage
is too meager to mention in TAFs with the 00Z TAF issuance.

After a lull through most of the night, scattered light rain showers
will develop again Saturday morning. Have kept prevailing rain
mention to FKL/DUJ during the late afternoon, while the rest of the
terminals should have a chance for scattered showers most of the day.
Did not want to go with long stretches of VCTS even though thunder
will be possible through most of the day. Tried to pick out two time
periods when there will be a greater chance of thunderstorms:
added a PROB30 for thunderstorms during the early afternoon with a
line of thunderstorms that may develop, then added VCTS in the
extended portion of the PIT TAF as high-resolution models suggest a
line of thunderstorms may move across Lake Erie and into
Ohio/Pennsylvania. While restrictions will be possible in any
moderate/heavy shower/storm, the prevailing conditions should be VFR.

Periodic restrictions are possible Sunday with additional showers and
thunderstorms along a stationary boundary. Additional rounds of
precipitation is expected after Tuesday.




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