MD 1879 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR PORTIONS OF SOUTHWESTERN SD AND NORTHWESTERN NE
Mesoscale Discussion 1879
NWS Storm Prediction Center Norman OK
0117 PM CDT Sun Aug 11 2024
Areas affected…Portions of southwestern SD and northwestern NE
Concerning…Severe potential…Watch possible
Valid 111817Z – 112015Z
Probability of Watch Issuance…40 percent
SUMMARY…Portions of southwestern South Dakota into northwestern
Nebraska are being monitored for a possible Severe Thunderstorm
Watch.
DISCUSSION…Isolated to widely scattered thunderstorms are evolving
over far northeastern WY and over the Black Hills early this
afternoon — likely aided by ascent preceding a midlevel shortwave
trough (and associated MCV) tracking eastward across southwest MT,
and heating over the higher terrain. Continue diurnal
heating/destabilization amid middle/upper 50s to lower 60s dewpoints
will continue to erode boundary-layer inhibition and contribute to
500-1000 J/kg MLCAPE. This, coupled with long/mostly straight
hodographs (around 40-45 kt of effective shear), will support a
gradual increase in thunderstorm intensity/organization through the
afternoon. The primary concern with any initial
semi-discrete/splitting supercell structures is large hail
(generally 1.5-1.75 inches) and locally severe gusts. Thunderstorms
will generally track southeastward into northwestern Nebraska
through the afternoon, where continued heating will support a
corridor of sufficient (albeit weak) surface-based instability for a
continued severe risk.
There is uncertainty on the overall coverage of severe thunderstorms
across the area, and the need for a watch is uncertain.
..Weinman/Hart.. 08/11/2024
…Please see www.spc.noaa.gov for graphic product…
ATTN…WFO…LBF…UNR…CYS…
LAT…LON 43810397 44330401 44510388 44650348 44600304 44410225
44060146 43400067 42800059 42200073 41920133 41770240
41950340 42380361 43370387 43810397
