Mesoscale Discussion 1663
Issued: · Valid: –
Summary
Severe thunderstorms capable of producing large hail and damaging wind gusts are expected to develop across portions of southern North Dakota and northern South Dakota through this evening. These storms may bring significant wind gusts of up to 80 mph and large hail exceeding 2 inches in diameter.
Product Text
000 ACUS11 KWNS 192056 SWOMCD SPC MCD 192055 NDZ000-SDZ000-192300- Mesoscale Discussion 1663 NWS Storm Prediction Center Norman OK 0355 PM CDT Sun Jul 19 2026 Areas affected...portions of southern North Dakota into northern South Dakota Concerning...Severe potential...Severe Thunderstorm Watch likely Valid 192055Z - 192300Z Probability of Watch Issuance...80 percent SUMMARY...Developing, high-based convection will evolve eastward through this evening, bringing a risk for severe wind gusts (some potentially significant) and large hail, perhaps to 2-3+ inches in diameter. DISCUSSION...A developing cumulus field across far southwestern ND/northwestern SD has shown some signs of increased vertical growth over the past hour, with isolated thunderstorms noted across Perkins and Meade Counties in South Dakota as of 2050 UTC. Additional development is expected amid continued insolation and along a southeastward-progressing cold front over the next couple of hours. A modified 18z BIS sounding indicates steep low- and mid-level lapse rates are in place across this region along with around 30 kts of effective shear and relatively straight, elongated hodographs. Coupled with strengthening upper-level flow and further hodograph elongation with time, this environment will be supportive of initial, high-based splitting supercells capable of large hail (potentially to 2-3+ inches in diameter) and severe outflow wind gusts to 80+ mph. Efficient evaporative cooling will favor cold pool development, with upscale growth into one or more clusters (and a transition towards severe wind gusts as the primary threat) then expected as convection spreads eastward with time. A Severe Thunderstorm Watch will likely be needed later this afternoon to cover this severe potential. ..Chalmers/Thompson.. 07/19/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FGF...ABR...BIS...UNR... LAT...LON 46600306 47240277 47560236 47740141 47750043 47659973 47419909 47049869 46319820 45639824 45119891 44899991 44790092 44800171 45010249 45300275 45970300 46600306 MOST PROBABLE PEAK WIND GUST...75-90 MPH MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN