Mesoscale Discussion 1334
NWS Storm Prediction Center Norman OK
0504 PM CDT Fri Jul 23 2021
Areas affected...southern North Dakota into northern South Dakota
Concerning...Severe potential...Watch possible=20
Valid 232204Z - 240100Z
Probability of Watch Issuance...60 percent
SUMMARY...Scattered storms are expected to form through evening,
either side of the North and South Dakota border. Large hail and
severe gusts will be possible.
DISCUSSION...Surface analysis shows a pressure trough from central
SD curling northeastward toward the Red River, with mid/upper 90s
temperatures common. A diffuse midlevel temperature gradient exists
across the Dakotas from north to south, with 500 mb temperatures to
-10 C near KBIS. Objective analysis indicates MLCAPE near 2000 J/kg,
with deep-layer shear approaching 50 kt.
Gradual height falls will occur through the evening, with increasing northwesterly 850 mb winds developing from northwest to southeast
across the western Dakotas. Increasing lift may thus result in one
or more clusters of severe storms with east/southeast motion.
Isolated peak-heating storms may also form over northwest SD (west
of an extensive cloud deck), or near the Black Hills, with hail and
A watch could be required later this evening if it becomes apparent
severe storm coverage will be more than isolated.
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