333 ACUS11 KWNS 201707 SWOMCD SPC MCD 201706 WVZ000-OHZ000-VAZ000-KYZ000-201900- Mesoscale Discussion 0802 NWS Storm Prediction Center Norman OK 1206 PM CDT Wed May 20 2026 Areas affected...portions of the mid/upper Ohio Valley Concerning...Severe potential...Watch possible Valid 201706Z - 201900Z Probability of Watch Issuance...40 percent SUMMARY...Scattered thunderstorms will pose a risk for damaging wind gusts and isolated marginally severe hail through this evening. A Severe Thunderstorm Watch may be needed in the next 1-2 hours. DISCUSSION...Latest radar imagery and lightning data depict increasing thunderstorm coverage ahead of an approaching cold front across portions of the mid/upper Ohio Valley. Continued insolation has resulted in temperatures warming into the lower 80s F, with around 500 J/kg MLCAPE depicted via latest objective analysis. Continued diurnal heating is expected to result in further destabilization, with 500-1000+ J/kg MLCAPE expected by peak heating this afternoon. As convective inhibition continues to erode, expectation is for thunderstorm coverage to increase, with modest effective shear of 20-30 kts supporting multicells and perhaps marginal supercells. Steepening low-level lapse rates and dewpoint depressions of 20+ F will support damaging wind gusts as the primary hazard, especially with any clusters that can become better organized. Isolated marginally severe hail may also be possible with more robust updrafts despite only modest effective shear and weak mid-level lapse rates (as sampled by the 12z ILN observed sounding). While severe coverage/magnitude are expected to remain marginally more limited compared to areas farther east (e.g., the Mid-Atlantic), a Severe Thunderstorm Watch may be needed for a portion of the discussion area in the next 1-2 hours. ..Chalmers/Hart.. 05/20/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...RNK...RLX...JKL...ILN...LMK... LAT...LON 38998292 39348225 39538147 39518089 39358032 39137988 38887967 38507975 37858072 37418187 37078310 37028390 37328453 37688459 38088434 38998292 MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN  877 ACUS11 KWNS 201734 SWOMCD SPC MCD 201734 TNZ000-KYZ000-201930- Mesoscale Discussion 0803 NWS Storm Prediction Center Norman OK 1234 PM CDT Wed May 20 2026 Areas affected...portions of Middle/eastern Tennessee into southern Kentucky Concerning...Severe potential...Watch unlikely Valid 201734Z - 201930Z Probability of Watch Issuance...20 percent SUMMARY...Widely scattered thunderstorms may pose a risk for isolated damaging wind gusts and small to marginally severe hail through this evening. Watch issuance is unlikely at this time. DISCUSSION...Recent radar imagery depicts increasing thunderstorm coverage across portions of Middle/eastern Tennessee and southern Kentucky amid continued diurnal heating of a moist low-level air mass (dewpoints in the mid/upper 60s F). Latest objective analysis depicts only weak buoyancy across the region, with MLCAPE around 500 J/kg. Further destabilization is expected through peak heating this afternoon, a modified 12z BNA observed sounding suggesting that MLCAPE is likely approaching 1000 J/kg based on recent surface observations. While deep-layer flow remains weak across the region (less than 30 kts of flow sampled through the column by the latest OHX VWP), 20-25 kts of effective shear should be sufficient to support modest updraft organization into a multicellular storm mode. In conjunction with steepening low-level lapse rates, this may promote the potential for gusty to isolated damaging wind gusts (likely in the 40-50 mph range) with any stronger, more well-organized clusters. Isolated small to marginally severe hail may also accompany the most robust updrafts despite poor mid-level lapse rates (5.5-6.0 C/km per latest mesoanalysis). Given the expectation for severe coverage/magnitude to remain limited, watch issuance is unlikely at this time. ..Chalmers/Hart.. 05/20/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MRX...JKL...LMK...OHX...HUN... LAT...LON 35788453 35418508 35058572 35018638 35208688 35548695 35958683 36358658 37218594 37588530 37558493 37368442 37068389 36748381 36258391 35788453 MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN  698 ACUS11 KWNS 201752 SWOMCD SPC MCD 201752 RIZ000-CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-201845- Mesoscale Discussion 0804 NWS Storm Prediction Center Norman OK 1252 PM CDT Wed May 20 2026 Areas affected...portions of the Mid-Atlantic into southern New England Concerning...Severe potential...Severe Thunderstorm Watch likely Valid 201752Z - 201845Z Probability of Watch Issuance...80 percent SUMMARY...Widely scattered thunderstorms will bring a risk for damaging wind gusts and isolated large hail through this evening. A Severe Thunderstorm Watch will be needed soon. DISCUSSION...Latest surface observations indicate that surface temperatures have warmed into the low 90s F across portion of the Mid-Atlantic. Coupled with mid-60s F dewpoints, this is supporting 500-1000+ J/kg MLCAPE across the area, with further destabilization expected through peak heating this afternoon. Expectation is for ongoing thunderstorm activity across Severe Thunderstorm Watch 234 to expand eastward, with additional development also possible along an approaching cold front. 20-30 kts of effective shear will support multicells, and perhaps marginal supercells. Steep low-level lapse rates (8+ C/km per latest objective analysis) and dewpoint depressions of 20-25+ F will promote the potential for damaging wind gusts, especially with any more well-organized clusters that develop. Isolated large hail may also accompany the most robust updrafts. A new Severe Thunderstorm Watch will be needed soon. ..Chalmers/Hart.. 05/20/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BOX...OKX...ALY...PHI...BGM... LAT...LON 40567574 40837554 41157502 41447382 41547334 41607289 41607231 41517205 41297181 41077177 40877191 40667263 40517332 40347368 39997393 39627403 39217449 39127488 39147530 39327557 39787578 40567574 MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN