Subj : DAY2SVR: Nws Storm Predic To : All From : Mike Powell Date : Thu May 11 2023 15:31:00 ACUS02 KWNS 111725 SWODY2 SPC AC 111723 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1223 PM CDT Thu May 11 2023 Valid 121200Z - 131200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THE MID-MISSOURI RIVER VALLEY AND ACROSS THE SOUTHERN PLAINS TO THE RIO GRANDE VALLEY... ....SUMMARY... Strong/severe storms are expected to begin during the afternoon, across a broad area extending from the Mid-Missouri Valley southward to the Rio Grande Valley. Very large hail and damaging wind gusts will likely be the primary severe threats over the southern half of the area into the overnight hours, while damaging winds and hail, and a couple of tornadoes, will be possible across the Mid Missouri Valley area through the evening. ....Synopsis... The upper-level wave currently migrating northeast across western KS is forecast to continue to the northeast over the next 48 hours, reaching the mid-MO Valley by mid/late afternoon. In general, this feature, and an attendant surface low, will de-amplify through the period with an associated weakening of mid/upper-level flow outside of the mid-MO Valley. A surface trough/dryline should be draped from eastern NE southward through central KS/OK and into TX by late afternoon and will act as a foci for convective initiation. To the south, mid-morning water-vapor imagery depicts a shortwave trough approaching Baja CA. This wave should reach the Big Bend region by tomorrow afternoon/evening, and will augment orographically-driven ascent, fostering scattered thunderstorm development along the Rio Grande. ....Mid Missouri River Valley... A reservoir of low 60s dewpoints is noted in morning surface observations across much of the central Plains. Persistent south/southeasterly flow over the next 36 hours ahead of the approaching surface low will maintain some poleward moisture advection, and some solutions suggest dewpoints may reach the mid-60s. Regardless, cool temperatures aloft associated with the upper-low will result in mid-level lapse rates near 7-7.5 C/km. Combined with the aforementioned low-level moisture, this should support MLCAPE values approaching 2000-3000 J/kg by late afternoon. Given the lack of an appreciable EML, diurnal warming should erode any mixed-layer inhibition and allow convective initiation along the surface trough/dryline. Initial convection will likely manifest as an arching band of discrete/semi-discrete cells with an attendant hail/wind risk. A few tornadoes are also possible given veered low-level winds and modest effective SRH ahead of the dryline. Upscale growth into one or more organized clusters is probable through the evening given deep-layer meridional flow oriented largely along the boundary - especially across southeast NE into adjacent areas of IA, KS, and MO. A corridor of several, perhaps longer-lived, supercells may emerge across portions of northeast NE where deep-layer shear orientations will be nearly orthogonal to the dryline. If this scenario occurs the large hail/tornado threat may be locally maximized. A significant hail area has been introduced to reflect the conditional nature of the threat. However, confidence in the spatial extent of this threat appears too limited in this forecast cycle for a categorical upgrade. ....Central OK to the Rio Grande... A migratory dryline should be draped from northeast KS through central OK and into western TX by late afternoon, though forecast uncertainty remains somewhat high in the exact placement of this feature by peak heating. This region will be well displaced from the stronger forcing for ascent to the north, but forecast soundings suggest residence time within the dryline circulation and strong diurnal warming will be sufficient for convective initiation along the boundary. Additional cells will likely develop off the terrain in northern Mexico, and should migrate east/northeast into southern TX. High-quality moisture return (dewpoints into the low 70s), coupled with temperatures in the low 80s will support strong buoyancy (MLCAPE near 4000 J/kg in some guidance). Mid and upper-level winds are forecast to be modest, only around 25-30 knots, but may be adequate for storm organization - especially across central/southern OK. Further south towards the Rio Grande, hodograph structure becomes more nebulous amid weak flow aloft, but the combination of ample buoyancy and a deep, well-mixed boundary layer will support the potential for strong downburst winds and large hail with initial updraft pulses. Through the evening, initially discrete/semi-discrete cells will likely see cold pool amalgamation/consolidation, resulting in upscale growth into a loosely organized, cold-pool driven MCS. As this occurs, the potential for severe winds should increase across central TX. The strengthening of a low-level jet over southern TX may allow for MCS maintenance overnight to near the TX Coastal Plain by 12 UTC Saturday (though the intensity of the MCS with eastward extent remains uncertain). ...Moore/Leitman.. 05/11/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .