Mesoscale Discussion 0715
NWS Storm Prediction Center Norman OK
0625 PM CDT Sun May 23 2021
Areas affected...Western South Dakota...Southwestern North Dakota
Concerning...Tornado Watch 197...
Valid 232325Z - 240100Z
The severe weather threat for Tornado Watch 197 continues.
SUMMARY...Severe threat continues across all but the southwestern
portions of ww197.
DISCUSSION...Surface warm front is advancing slowly north across
northwestern SD/southern ND early this evening. As a result,
buoyancy is gradually increasing across extreme southern ND where
surface temperatures have warmed into the lower 70s. One long-lived
supercell that matured earlier across western SD has lifted to near
Lemmon and will soon cross the warm front. This storm has produced a
few tornadoes over southeastern Perkins County SD, and until it
becomes elevated north of the warm front some tornado threat
remains. Otherwise, an arcing band of organized convection has
emerged from the northern Black Hills into northwestern NE. This
activity should continue surging northeast across the remainder of southeastern/central portions of the watch, eventually spreading
toward the ND border later this evening. Tornado threat remains
highest with discrete supercells ahead of the squall line.
There is some concern that low-level warm advection will begin to
enhance the elevated convective threat north of the warm front over
western ND over the next few hours. Forecast soundings suggest hail
will be the biggest concern with this activity and some
consideration is being given for a potential severe thunderstorm
watch over this region.
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