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Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0357 AM CDT Fri May 20 2022

Valid 231200Z - 281200Z

...DISCUSSION...
...Monday/Day 4 to Wednesday/Day 6...
On Monday, an upper-level trough is forecast to move across the
southern and central Rockies. Ahead of the trough, low-level
moisture return is forecast over the southern Plains, where pockets
of moderate instability may develop during the afternoon.
Thunderstorm development will be likely over parts of the southern
Plains along pre-existing boundaries and near thermal gradients.
However, the stronger mid-level flow is forecast to stay further
north. This will keep the potential for organized thunderstorms
relatively low. A marginal severe threat will be possible in areas
where the strongest instability develops.

On Tuesday, the models are in relatively good agreement that an
upper-level trough will move into the southern and central Plains.
Ahead of the trough, low-level moisture advection is forecast over
the lower to mid Mississippi Valley. A large area will have
potential for thunderstorms from Texas northeastward into the Ohio
Valley. The strongest instability is forecast over the southern half
of Texas. Organized thunderstorms could occur along the northern
edge of the stronger instability from the Texas Hill Country
east-northeastward into the Arklatex. But mesoscale aspects of the
forecast make predictability low, an outflow boundaries and local
convergence zones will be key to where the greatest convective
potential is realized Tuesday afternoon.

On Wednesday, the models continue to move an upper-level trough
slowly eastward across the southern Plains. A cold front is forecast
to move into the southern Plains, Arklatex and mid Mississippi
Valley. Thunderstorm development will again be possible across a
broad area from the southern Plains northeastward into the Ohio and
Tennessee Valleys. There is a lot of uncertainty on Wednesday's
forecast. The models vary on where the front will be, and have large
differences in the distribution of instability. It appears that an
MCS could develop across parts of central and east Texas, but this
will depend upon a number of factors that are more mesoscale in
nature.

Further northeast on Wednesday, thunderstorm development will also
be likely in parts of the mid Mississippi and Ohio Valleys.
Instability could be sufficient in some areas for a severe threat
Wednesday afternoon. However, the models have yet to show a
concentrated area with increased severe potential.

Concerning the early to mid week time-frame, a severe threat area
could be added in later outlooks as model forecasts beco*e more
conclusive concerning key elements for severe potential.

...Thursday/Day 7 and Friday/Day 8...
From Thursday into Friday, an upper-level low is forecast to
continue moving slowly eastward from the Mississippi Valley into the
eastern U.S. Ahead of the associated trough, a cold front is
forecast to advance east-southeastward across the southern third of
the nation. Thunderstorm development will be likely along and ahead
of the front each day. An isolated severe threat could develop in
areas that destabilize the most during the afternoon and evening on
both Thursday and Friday. It would seem that the greatest severe
threat would be over the southern Appalachians Thursday afternoon,
where low-level flow is forecast be maximized. However, much
uncertainty exists from Thursday into Friday, mainly due to large
differences in the model solutions.