Mesoscale Discussion 1699 NWS Storm Prediction Center Norman OK 0448 PM CDT Tue Jul 21 2026 Areas affected...Kentucky into northern Tennessee and far western Virginia Concerning...Severe Thunderstorm Watch 508... Valid 212148Z - 212345Z The severe weather threat for Severe Thunderstorm Watch 508 continues. SUMMARY...The potential for damaging winds, large hail, and perhaps a tornado or two is expected to spread south of the watch area between 23Z and 00Z. A new watch will be required prior to that time. DISCUSSION...Regional radar imagery shows a mix of supercells and bowing structures ongoing across eastern and central parts of the watch area with more recent storm development present near the confluence of the Mississippi and Ohio Rivers. The inflow air mass to the storms is warm and quite moist with MLCAPE of 2500-3500+ J/kg, per recent objective analysis. However, considerable downshear anvil blowoff has limited the potential for stronger insolation across the warm sector, which in turn is resulting in relatively poor low-level lapse rates. Kinematically, regional VWPs are sampling seasonably strong mid- and high-level winds and resultant deep-layer shear with the strongest low-level shear currently analyzed from eastern KY into western WV. Extrapolation of current storm motions takes the storms to the southern edge of the watch area between 23Z and 00Z with latest CAM guidance suggesting the storms will remain intense as they continue into portions of TN and far western VA. That scenario appears reasonable given the presence of the strong vertical shear. Expect the continuation of supercell and bowing structures with the primary hazards being damaging winds and large hail. The extent of the longer-term tornado threat remains somewhat uncertain owing to the weaker low-level lapse rates, which may limit near-ground parcel accelerations. However, in the near-term, the greatest tornado risk will extend from the tornadic supercell in Hart County KY, into eastern KY where low-level shear is the strongest. ..Mead.. 07/21/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...RLX...MRX...JKL...ILN...LMK...OHX...PAH...MEG... LAT...LON 36228986 36678976 37848656 38748303 38308240 37598192 36858211 36248375 35928569 36118836 36218938 36228986 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
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