Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Mon Oct 02 2023 08:53:00 ACUS01 KWNS 021228 SWODY1 SPC AC 021227 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0727 AM CDT Mon Oct 02 2023 Valid 021300Z - 031200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN NEW MEXICO AND ADJACENT WESTERN TEXAS... ....SUMMARY... Thunderstorms, associated with large hail and wind damage, will be possible this afternoon and evening across parts of the southern Rockies and southern High Plains. Marginally severe storms will be possible in parts of the central Rockies, and in parts of the central and northern Plains. ....Synopsis... An amplified upper trough over the Intermountain West will shift east today/tonight toward the Rockies/High Plains. An associated belt of enhanced deep-layer south/southwesterly flow will overspread the Rockies and adjacent High Plains. Deep-layer flow will be rather meridional through the central/northern High Plains, with somewhat more southwesterly flow focused over the southern High Plains vicinity. At the surface, lee troughing will extend along much of the High Plains. Some stronger surface cyclogenesis is forecast from the WY/SD/NE vicinity into the central Dakotas during the latter half of the forecast period. Southerly low-level flow will result in modest boundary-layer moisture (50s to low 60s F) near/to the east of the surface trough axis. With northward extent into the Dakotas, capping in the 850-700 mb layer will largely preclude surface-based convection. Further south, deep boundary-layer mixing and somewhat better low-level moisture will allow for more surface-based convection. Isolated to scattered strong/severe thunderstorms are expected this afternoon into tonight across from the southern High Plains vicinity into parts of the Dakotas. The main hazards with this activity will be large hail and strong/severe gusts. ....Southern Rockies/High Plains vicinity... Focused severe potential will be aided by higher quality boundary-layer moisture (supporting moderate instability), and vertically veering wind profiles, indicating supercell potential. A few rounds of thunderstorms are possible in a persistent low-level upslope flow regime, with severe potential increasing by mid-afternoon and persisting into evening. Forecast hodograph show modest low-level curvature due to relatively weak low-level flow through 1-2 km. However, hodographs becoming elongated/straight above this layer. Favorable thermodynamics and shear should support large hail potential, while steep low-level lapse rates suggest strong outflow gusts will be possible. ....Central High Plains into the Dakotas... A low will deepen over far southeast WY today, while southerly low-level flow ahead of the low maintains 50s F surface dewpoints. Stronger heating focused across northeast CO/far southeast WY into western NE will aid in a corridor of moderate instability. With northward extent into the Dakotas, capping will limit surface-based instability. Initial thunderstorm development is expected by late afternoon near the surface low vicinity. Isolated hail and strong gusts will be possible with this activity. An organized thunderstorm cluster will likely shift north/northeast during the evening/early overnight period across parts of western SD into western/central ND. This activity will be elevated above a capping inversion and mainly pose a risk for sporadic hail. ...Leitman/Thompson.. 10/02/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .