Mesoscale Discussion 1218 NWS Storm Prediction Center Norman OK 0753 PM CDT Sat Jun 20 2026 Areas affected...portions of Nebraska Sandhills Concerning...Severe Thunderstorm Watch 360... Valid 210053Z - 210230Z The severe weather threat for Severe Thunderstorm Watch 360 continues. SUMMARY...An elevated supercell developed across portions of the Nebraska Sandhills this evening. Large hail and damaging wind will be possible as this storm moves east. Additional thunderstorms may also develop later this evening and be capable of large hail and damaging winds as well. DISCUSSION...An isolated supercell has developed across the Nebraska Sandhills. This eastward moving storm has quickly intensified, with MRMS hail estimates approaching 2". The observed 00Z sounding from North Platte, NE, indicates a strongly sheared and modestly unstable environment across the region. Low-levels are largely stable, with a 0-3 kilometer lapse rate of 4 C/km beneath a strong inversion just below 700 millibars. Thus, the ongoing supercell is elevated and likely rooted at or slightly above this inversion. That said, parcels originating at this level are unstable, with MUCAPE around 1200 J/kg and effective layer shear in excess of 50 knots. This environment should support continued hail across the area this evening. Additionally, DCAPE from the sounding is around 1000 J/kg so isolated damaging wind gusts are also possible. With continued warm-air advection atop this stable boundary layer, additional thunderstorms may be possible later this evening. Additionally, a cluster of thunderstorms will move east out of Wyoming and the Nebraska panhandle later this evening. Given the overall environment, large hail and damaging winds would be possible with those storms as well. Recently issued Severe Thunderstorm Watch #360 was issued to address these threats. ..Marsh/Smith.. 06/21/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GID...LBF...UNR...CYS... LAT...LON 42970277 43010026 40710021 40660124 40990127 41010256 41970269 42970277 MOST PROBABLE PEAK WIND GUST...65-80 MPH MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
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