South Dakota Mesoscale Discussion

Areas affected…much of central Nebraska

Concerning…Severe Thunderstorm Watch 646…

Valid 120114Z – 120315Z

The severe weather threat for Severe Thunderstorm Watch 646

SUMMARY…The threat for damaging hail and wind will continue across
much of central Nebraska this evening.

DISCUSSION…Numerous strong to severe storms were ongoing as of 01Z
from northeast CO into central NE, along multiple boundaries. The
00Z soundings from DNR and LBF both showed substantial instability,
with impressive winds aloft for this time of year. Although winds
aloft will continue to increase as the upper trough approaches,
there are hodograph weaknesses related to veering then backing winds
with height. As a result, storm modes have been mixed across the
region. Regardless, cold temperatures aloft and favorable
large-scale lift will continue to support severe storms with
damaging hail. Some of the larger storms may also produce damaging
winds as downdrafts will be cold and hail-laden. An increasing
low-level jet may allow leading cells over central NE (near the
stationary front) to grow upscale a bit, possibly with a damaging
wind threat. A brief tornado cannot be ruled out anywhere east of
the cold front as low-level shear remains sufficient, with mixed
storm mode being the main mitigating factor.

..Jewell.. 09/12/2019

…Please see for graphic product…


LAT…LON 40180314 40260412 40510401 41340328 41580254 42140194
43010136 42999849 42869818 42259821 41779835 40349975

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