Areas affected…South Dakota
Concerning…Tornado Watch 564…
Valid 092043Z – 092215Z
The severe weather threat for Tornado Watch 564 continues.
SUMMARY…The threat for severe wind, hail, and possibly a few
tornadoes continues across much of SD. Some upscale growth is
possible late this afternoon into the early evening, which would
result in an increasing severe wind threat with time.
DISCUSSION…One surface-based supercell is ongoing across
south-central SD as of 2045Z, with other convection across the area
generally near or north of the effective warm front. In the short
term, a hail and locally severe wind risk will continue with the
ongoing supercell and any semi-discrete cells that evolve out of the
convection further north, given the presence of moderate buoyancy
(MLCAPE of 1500-2500 J/kg) and effective shear of 40-50 kt.
The tornado threat will be contingent on supercell interaction with
the effective warm frontal zone. The ongoing supercell across
south-central SD has thus far tracked slightly south of the
effective boundary, though if it continues to track eastward, it may
come in closer proximity to the warm front, which is oriented more
northwest/southeast with eastward extent. If any semi-discrete
supercells can evolve out of the slightly elevated convection to the
north, they would also pose a tornado threat as they propagate
east-southeast within a helicity-rich environment. The cells
near/north of Pierre as of 2045Z may pose the greatest short-term
tornado threat, given their proximity to the front.
Otherwise, a tendency for upscale growth is expected with time as
convection congeals over central SD, with a southeastward-moving
complex capable of potentially more widespread severe wind possible
by early evening into a larger portion of south-central/southeast
…Please see www.spc.noaa.gov for graphic product…
LAT…LON 43310151 43680195 44560179 44750123 44760006 44659927
44559861 44409810 43879767 43339756 43189787 43179889