ZCZC SPCSWOMCD ALL ACUS11 KWNS 040138 SPC MCD 040138 MOZ000-ARZ000-LAZ000-TXZ000-OKZ000-040345- Mesoscale Discussion 0511 NWS Storm Prediction Center Norman OK 0838 PM CDT Mon May 03 2021 Areas affected...Portions of northeast TX...far southeastern OK...extreme northwestern LA...much of AR...and far southern MO Concerning...Severe potential...Watch likely Valid 040138Z - 040345Z Probability of Watch Issuance...95 percent SUMMARY...The severe threat will increase this evening as storms approach from the west. Damaging winds should become an increasing concern. Isolated large hail and a couple tornadoes may also occur. Watch issuance is very likely. DISCUSSION...The OOZ sounding from LZK showed a very unstable airmass is present across much of AR to the south of a front, with around 3800 J/kg of MLCAPE observed. Robust, severe storms ongoing across north-central TX and eastern OK are expected to move eastward this evening into parts of northeast TX, much of AR, and eventually far southern MO later this evening. With generally upper 60s to mid 70s surface dewpoints and steep mid-level lapse rates in place across these areas, moderate to strong instability will likely persist through much of the evening and early overnight hours, even with the loss of daytime heating. Enhanced mid-level flow associated with a shortwave trough over the southern Plains will overspread this region, with around 35-45 kt of effective bulk shear supporting continued storm organization and intensity. An ongoing cluster of storms in eastern OK has recently produced a measured severe wind gust to 71 mph. Current expectations are for this cluster to continue growing upscale this evening as it moves into AR, with additional severe storms potentially developing from north-central into northeast TX. Both large hail and damaging wind gusts will be a concern given the large reservoir of buoyancy available. But, scattered to numerous severe/damaging winds will likely become the primary concern as the storm mode becomes increasingly linear across AR this evening. Given the steep lapse rates aloft, there may be some potential for significant severe wind gusts (75+ mph) if storms form into a bowing complex. Finally, even though low-level flow is not forecast to be very strong, a couple tornadoes also appear possible with any embedded circulations given around 100-150 ms/s2 of effective SRH forecast. With the overall severe threat expected to increase in the next couple of hours, watch issuance will be needed. ..Gleason/Thompson.. 05/04/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...PAH...MEG...LZK...SGF...SHV...TSA... LAT...LON 32939518 34359493 34459440 35439435 36159450 36639325 36879169 36879078 36749009 36518976 36068982 34949053 34359109 33579225 32739413 32289497 32169540 32939518 NNNN