Mesoscale Discussion 1362 NWS Storm Prediction Center Norman OK 1038 PM CDT Sat Jun 27 2026 Areas affected...parts of north central Nebraska through south central and southeastern South Dakota Concerning...Tornado Watch 406... Valid 280338Z - 280545Z The severe weather threat for Tornado Watch 406 continues. SUMMARY...Intensifying thunderstorms, perhaps including evolving supercell structures ahead of an increasingly organized cluster, are likely to pose an increasing risk for strong to severe wind gusts, large hail and perhaps a couple of tornadoes through midnight to 2 am CDT, near and north of the Nebraska/South Dakota state border area. A new severe weather watch will likely be needed within the next hour or so. DISCUSSION...Warmer elevated mixed-layer air (as generally depicted by 16-18 C temperatures around 700 mb) continues to nose northeast of the southern Rockies, downstream of the broad mid-level low centered over the Northwest. As this continues through late evening, latest Rapid Refresh suggests that a 700 mb thermal gradient demarcating the stronger mid-level inhibition will focus near the Nebraska/South Dakota state border by 05-07Z. Beneath this regime, it appears that a surface cyclone is undergoing further deepening as it migrates across and northeast of the Cheyenne Ridge vicinity of the high plains. As this continues, a southerly 850 mb jet across the Panhandle vicinity through north central Nebraska is forecast to undergo notable further strengthening to 50-60+ kt. It appears that strengthening low-level convergence and warm advection near the nose of this jet, where inflow of seasonably high moisture content with sizable potential instability will be maintained, will support potential for substantive further intensification, upscale growth and organization of ongoing convection. The evolution of preceding supercell structures might also not be out of the question, posing a risk for large hail and perhaps a couple of tornadoes, while the potential for strong to severe wind gusts increases with the evolving larger-scale convective system. ..Kerr.. 06/28/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FSD...ABR...LBF...UNR... LAT...LON 43340151 43740029 44059839 43209780 42369995 42490154 43340151 MOST PROBABLE PEAK TORNADO INTENSITY...100-125 MPH MOST PROBABLE PEAK WIND GUST...75-90 MPH MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
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