First noteworthy MD of the event
Mesoscale Discussion 0484
NWS Storm Prediction Center Norman OK
0155 PM CDT Tue Apr 28 2020
Areas affected...southeast Kansas...eastern Oklahoma...southwest
Missouri...northwest Arkansas
Concerning...Severe potential...Watch likely
Valid 281855Z - 282130Z
Probability of Watch Issuance...95 percent
SUMMARY...Storms will develop by 21Z along and ahead of a cold
front, and quickly become severe. Damaging hail, wind, and a few
tornadoes are all possible.
DISCUSSION...A surface trough extends from western OK northeastward
across IA, with a low over northwest OK at 19Z. Meanwhile, a
stronger cold front was surging across central KS, and across the
Panhandles.
Strong instability has developed near the surface trough, beneath
very steep lapse rates aloft. Early and midday soundings show
700-500 mb lapse rates to around 9 C/km, beneath modest northwest
flow aloft. Meanwhile, southery surface winds are maintaining mid
60s F dewpoints south of the cold front, resulting in strong
instability.
Storms are likely to develop along and ahead of the surging front
over KS, and become severe as they encounter the stronger
instability. Large hail is likely initially, transitioning to
damaging winds. Initial cellular activity may produce a brief
tornado. As the storms move southward across eastern OK, access to
greater low-level SRH may yield a few tornadoes, perhaps with cells
in the line or brief QLCS.
Farther west, steep low-level lapse rates exist over western OK and
northwest TX, and this may help to eventually break the cap as the
wind shift moves south toward I-40 later today. While a capping
inversion does exist, the western fringe of the frontal storms will
likely be severe, producing damaging hail and wind.
..Jewell/Thompson.. 04/28/2020