Mesoscale Discussion 1689
Issued: · Valid: –
Summary
Strong to severe thunderstorms are expected to move across portions of the lower and middle Ohio River Valley this afternoon. These storms may bring damaging wind gusts, brief tornadoes, and isolated large hail.
Product Text
000 ACUS11 KWNS 211715 SWOMCD SPC MCD 211715 KYZ000-INZ000-TNZ000-ILZ000-MOZ000-ARZ000-211845- Mesoscale Discussion 1689 NWS Storm Prediction Center Norman OK 1215 PM CDT Tue Jul 21 2026 Areas affected...portions of the lower and middle Ohio River Valley Concerning...Severe potential...Watch likely Valid 211715Z - 211845Z Probability of Watch Issuance...80 percent SUMMARY...Numerous strong to severe thunderstorms are expected to form along a cold front this afternoon before progressing southeastward. Damaging to severe wind gusts will be the primary threat, with brief tornadoes and isolated large hail also possible. DISCUSSION...Latest surface analysis places a cold front extending southwestward from southern Lower Michigan into central Indiana, southern Illinois, and south-central Missouri. A deepening cumulus field is noted along and ahead of this cold front, with temperatures approaching the low-90s F and dewpoints near 80. Observational trends and latest high-res guidance suggest that robust convective initiation will occur across this region over the next 1-2 hours. Strong mid-level flow overspreading the region (~40 kts sampled around 3 km AGL by the LVX/VWX VAD profiles) and strong effective shear of 50+ kts will support initial supercells, but linear forcing along the front, widespread initiation, and cold pool conglomeration will promote rapid upscale growth into one or more linear segments/clusters. Damaging/severe wind gusts to around 70 mph are expected to be the most common hazard, but brief tornadoes and large hail to around golf ball size are also possible. Confidence is higher in greater storm coverage occurring from southern Indiana into northern Kentucky, with more uncertainty surrounding coverage existing farther west (where effective shear is also forecast to be modestly weaker). Given the expected severe risk, watch issuance is likely for at least a portion of the discussion area early this afternoon. ..Chalmers/Mosier.. 07/21/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LMK...OHX...IND...PAH...ILX...MEG... LAT...LON 36608692 36168805 35948908 35938997 36029029 36189042 36539042 37049025 37638953 38468788 38698738 38918669 39008617 39008586 38908553 38628524 38308505 37958492 37568500 37228527 36968589 36608692 MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN