South Dakota Mesoscale Discussion

Areas affected…Northern Nebraska and southeastern South Dakota

Concerning…Tornado Watch 640…

Valid 110107Z – 110230Z

The severe weather threat for Tornado Watch 640 continues.

SUMMARY…Thunderstorm activity may evolve into an increasing
organized cluster which could pose increasing potential for strong
wind gusts, mainly east-northeast of Valentine NE toward the Sioux
Falls SD area, between 10 PM and Midnight. A new severe weather
watch will likely be issued, replacing tornado watch 640 and severe
thunderstorm watch 642 before their 10 PM expiration.

DISCUSSION…Vigorous thunderstorm development is now largely
focused within the zone of stronger lower/mid tropospheric warm
advection, to the cool side of the surface front, across
northwestern and north central Nebraska into southeastern South
Dakota. Through 03-04Z, a southerly low-level jet is forecast to
continue intensifying (including 30-50 kt at 850 mb) across the
central Plains, with associated strongest forcing for ascent
becoming focused near or just east of Valentine NE. As this
concentrates inflow of seasonably moist air supportive of large
CAPE, a corridor of renewed intensifying and organizing convective
development appears possible, which may be accompanied increasing
potential for damaging winds. This is then expected to shift into
the Sioux Falls SD by 05-06Z, if not before.

..Kerr.. 09/11/2019

…Please see for graphic product…


LAT…LON 42650208 43060049 43539973 44139751 43379657 42469710
42130035 41910162 42650208

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