MD 0812 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR NORTHEAST MISSISSIPPI TO NORTHERN ALABAMA AND SOUTHERN MIDDLE TENNESSEE
Mesoscale Discussion 0812 NWS Storm Prediction Center Norman OK 0100 PM CDT Thu May 18 2023 Areas affected...Northeast Mississippi to northern Alabama and southern Middle Tennessee Concerning...Severe potential...Watch unlikely Valid 181800Z - 182000Z Probability of Watch Issuance...5 percent SUMMARY...Isolated strong downburst winds and occasional severe hail are possible this afternoon. This threat will remain too transient and localized to warrant watch issuance. DISCUSSION...Convective initiation is well underway across northern MS into northern AL in the vicinity of a weak surface low and attendant weak warm front/differential heating boundary draped to the east. Latest GOES imagery and lightning trends indicate that much of this convection is intensifying, likely owing to ample diurnal warming with temperatures warm through the upper 70s into the low 80s. Further warming, combined with cool temperatures aloft in the vicinity of a weak upper low, will support MLCAPE values upwards of 1500-2000 J/kg by mid-afternoon across northern AL to southern middle TN. Although deep-layer shear is fairly modest, favorable thermodynamics (aforementioned buoyancy combined with PWATs above 1.5 inches and low-level lapse rates near 8 C/km) will support the potential for damaging downburst winds as storms begin to cluster and propagate north/northeast. Additionally, sporadic hail approaching severe limits will be possible with the more intense updraft pulses, though storm longevity will likely remain too limited to support a substantial hail threat. Further south across south-central MS, stronger mid-level flow is likely supporting effective bulk shear values on the order of 25-30 knots within a similar thermodynamic environment. While this region is conditionally more favorable for organized severe convection, confidence in storm coverage remains very limited owing to very weak/localized forcing for ascent. ..Moore/Grams.. 05/18/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MRX...OHX...BMX...HUN...MEG...JAN... LAT...LON 33708646 33798715 33848805 33628863 33428928 33258984 33469011 34028983 34578923 35168803 35458737 35578695 35598632 35428601 35268587 34778570 34298557 33898568 33708601 33708646