Mesoscale Discussion 1800
Issued: · Valid: –
Summary
A cluster of thunderstorms capable of producing strong wind gusts of 55 to 70 mph may affect much of central South Dakota and north central Nebraska through approximately 1 AM CDT. The severity of these wind gusts is expected to diminish during this time.
Product Text
000 ACUS11 KWNS 300441 SWOMCD SPC MCD 300440 SDZ000-NEZ000-300645- Mesoscale Discussion 1800 NWS Storm Prediction Center Norman OK 1140 PM CDT Wed Jul 29 2026 Areas affected...much of central South Dakota...north central Nebraska Concerning...Severe potential...Watch unlikely Valid 300440Z - 300645Z Probability of Watch Issuance...5 percent SUMMARY...Ongoing cluster of thunderstorms may be slow to weaken, but associated strong to severe wind gusts probably will diminish through 1-3 AM CDT. DISCUSSION...Beneath mid/upper ridging, weakly sheared, southwesterly deep-layer mean flow on the order of 10-15 kt prevails across much of the middle Missouri Valley. However, forcing for ascent along the leading edge of the surface cold pool associated with consolidating outflows has been sufficient to maintain vigorous thunderstorm development east of the Black Hills into central South Dakota the past few hours. This, and an associated increase in strong to severe surface gusts, probably has been supported by a nocturnally strengthening boundary-layer jet (up to around 30 kt below 850 mb), near a weak surface low migrating across the Pierre vicinity. Despite the loss of daytime heating, moistening southeasterly near-surface flow ahead of activity across central South Dakota has been maintaining, or even contributing to a subtle increase in, potential instability. Whether this is enough to maintain convection supportive of continuing strong to severe surface gusts remains somewhat unclear. 04Z surface observations still indicate 2-hourly pressure rises on the order of 2-6+ mb within the cold pool. However, most recent radar, satellite and lightning data suggest that a more notable weakening trend in convective intensity may now be underway. As activity advances into an environment with progressively less steep mid-level lapse rates, and higher low-level moisture content with reduced latent cooling potential, the risk for severe wind gusts seems likely to diminish. ..Kerr/Smith.. 07/30/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FSD...ABR...LBF...UNR... LAT...LON 45350080 45229945 44139813 42929920 42260065 42770095 43590033 44140028 45050115 45350080 MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN