SPC MD 815

MD 0815 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF NORTHEASTERN COLORADO...SOUTHEAST WYOMING AND WESTERN NEBRASKA Mesoscale Discussion 0815 NWS Storm Prediction Center Norman OK 0319 PM CDT Thu May 21 2026 Areas affected...portions of northeastern Colorado...southeast Wyoming and western Nebraska Concerning...Severe potential...Watch possible Valid 212019Z - 212215Z Probability of Watch Issuance...60 percent SUMMARY...Thunderstorm development is expected to continue this afternoon with a few stronger storms possible. Supercells with a risk for hail, damaging gusts and perhaps a brief tornado are possible. A WW is being considered for parts of the area. DISCUSSION...As of 2015 UTC, visible and radar imagery showed showers and thunderstorms developing within the broad upslope flow regime from eastern WY into northeast CO and western NE. Aided by deep ascent from the approaching upper low over the northern Plains, diurnal heating has been somewhat muted by lingering low clouds. Surface dewpoints will gradually increase, with clearing and steep lapse rates eventually supporting moderate buoyancy. Area VADs show 40-50 kt of deep-layer shear supportive of organized supercells. Hail is the primary risk with these storms owing to steep lapse rates, cold mid-level temperatures and the elongated mid and upper-level hodographs. Damaging gusts will also be possible, especially to the west where low-level lapse rates are steeper. A tornado or two is also possible later this evening with increasing low-level shear and terrain influence, but this remains uncertain. Current expectations are for storms to increase in intensity over the next 2-3 hours but remain fairly isolated. Deepening cumulus has been noted along the Cheyenne Ridge and the Palmer Divide. These areas are likely to severe as the primary focus for stronger storm development this afternoon. Father north, weaker buoyancy will likely limit intensity, though an isolated severe threat could exist over southeastern WY and western NE. Given the expected increase in the severe risk with time, a WW is being considered. ..Lyons/Hart.. 05/21/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LBF...GLD...BOU...CYS... LAT...LON 41400261 41030229 40410211 39640206 39130230 39070277 39110357 39230431 39510463 40340475 41390494 41920469 42040397 41750281 41400261 MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN Read more