ZCZC SPCSWOMCD ALL ACUS11 KWNS 181711 SPC MCD 181711 ARZ000-TXZ000-OKZ000-181815- Mesoscale Discussion 0669 NWS Storm Prediction Center Norman OK 1211 PM CDT Sat May 18 2019 Areas affected...Parts of central through northeast Texas into southeastern Oklahoma and adjacent southwest Arkansas Concerning...Tornado Watch 181... Valid 181711Z - 181815Z The severe weather threat for Tornado Watch 181 continues. SUMMARY...The risk for severe winds may increase across parts of the Red River Valley, toward the Ark-La-Tex, through 1-3 PM CDT, while potential for severe hail and a couple of tornadoes increases in a possible corridor of developing supercells across the Texas Hill Country through northeastern Texas. DISCUSSION...The southern flank of the extensive ongoing mesoscale convective system is maintaining strength, with additional storms forming to the south of the primary cold pool, east of the dryline into portions of the Edwards Plateau. Activity is largely oriented parallel to 30-40 kt southwesterly deep layer ambient mean flow, resulting in only a modest general eastward progression. However, as the environment continues to warm ahead of the strengthening cold pool, the risk for potentially damaging winds may increase along east-northeastward surging segments of the gust front. Furthermore, as stronger upper support for large-scale ascent continues to gradually pivot across/northeast of the Red River Valley, toward the lower Missouri Valley, the primary convective mode across the Texas Hill country into northeast Texas may trend discrete/supercellular through 18-20Z. Residual mid-level capping associated with warm elevated mixed-layer air may suppress the development of widespread convection, but strong deep layer shear in the presence of moderate to large mixed-layer CAPE (2000-3000+ J/kg) will provide a favorable environment for supercells. It appears that southerly 850 mb flow will remain strong enough to contribute to low-level hodographs supportive of a risk for tornadoes, in addition to severe hail. ..Kerr.. 05/18/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LZK...SHV...TSA...HGX...FWD...OUN...EWX...SJT... LAT...LON 31049919 31649849 31909784 32339753 32639698 33359621 33709598 34809551 35239444 35119394 33639388 31419521 30329739 30149954 31049919 NNNN