111
ACUS48 KWNS 200835
SWOD48
SPC AC 200834

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0334 AM CDT Mon May 20 2024

Valid 231200Z - 281200Z

...DISCUSSION...
...Day 4/Thu - Great Plains...

A weak upper shortwave trough is expected to spread east from the
southern Rockies to the Mid-South on Thursday. As this occurs, a
band of enhanced southwesterly flow will overspread parts of OK and
the ArkLaTex vicinity. A very moist airmass will be in place as
southerly low-level flow maintains upper 60s to low 70s F dewpoints.
This will aid in strong to extreme instability across portions of
the southern Plains/ArkLaTex. While convective evolution is a bit
uncertain, the overall pattern will support severe-thunderstorm
potential.

A potent shortwave upper trough will move across the northern
Rockies to the northern Plains. As this occurs, a surface low will
deepen and move from the northern High Plains eastward across the
Dakotas. Some severe potential may accompany this system. However,
boundary-layer moisture will likely be poor given a prior cold
frontal passage and better-quality moisture return only making it as
far north as KS or southeast NE. Low-end severe probabilities may be
needed in future outlooks, but potential appears too low for a 15
percent delineation at this time.

...Days 5-8/Fri-Mon...

Spread among forecast guidance increases Day 5/Fri and beyond.
However, a general pattern where subtle upper shortwave troughs
emanate from the Rockies into the Plains and central U.S. will
likely continue. Forecast guidance varies in timing and location of
these features, but at least some severe-thunderstorm potential will
be possible from portions of the Plains into the Midwest/Mid-South
vicinity through the weekend. Given uncertainty, confidence is too
low to introduce 15 percent probabilities for any given area at this
time.

..Leitman.. 05/20/2024