Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Tue Apr 18 2023 17:19:00 ACUS01 KWNS 181943 SWODY1 SPC AC 181941 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0241 PM CDT Tue Apr 18 2023 Valid 182000Z - 191200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE CENTRAL STATES... ....SUMMARY... Isolated severe thunderstorms are possible from parts of the southern Great Plains northward into the Mid Missouri Valley/Upper Midwest and westward into Wyoming. Large hail and severe wind gusts will be the hazards with the stronger storms late this afternoon into tonight. ....Discussion... No change is warranted to the previous convective outlook. ...Smith.. 04/18/2023 ..PREV DISCUSSION... /ISSUED 1126 AM CDT Tue Apr 18 2023/ ....Central/southern Great Plains to Mid-MO Valley/Upper Midwest... Modified moisture return is occurring from the southern Great Plains ahead of a deepening lee cyclone over the central High Plains. But guidance has above-average spread in the degree of this return into KS and southern NE by early evening, lowering confidence in the overall environment and sustenance of deep convection given the stout elevated mixed-layer over the moist sector. Based on 12Z observed soundings, GOES PW imagery, and 16Z surface observations, it appears that the drier spectrum of guidance is more reasonable with the magnitude of this return, suggesting mid 40s to mid 50s surface dew points north of OK by 00Z. This should be adequate to support isolated high-based thunderstorms along the dryline in the western KS vicinity during the late afternoon to early evening. This activity will pose a threat for isolated large hail and localized severe wind gusts. Still, morning HRRR runs are insistent that even this scenario will fail, with effectively no sustained deep convection along the entire dryline. During the evening, a strengthening low-level jet will yield warm theta-e advection tonight. This might support any lingering dryline storms spreading northeast towards the Mid-MO Valley or more likely the development of elevated thunderstorms where ascent can overcome the stout elevated mixed-layer. Steep mid-level lapse rates and favorable cloud-layer shear will conditionally support a few elevated supercells, although the predominant convective mode should tend towards clusters northeast of the surface warm front. Isolated large hail appears to be the main threat. ....WY to western SD/NE... An elongated upper trough over the Northwest should consolidate across the northern Great Plains tonight. This will occur as a piece of the strong mid-level jet across northern/central CA and the Sierras ejects across the central Rockies to the Black Hills vicinity. This strengthening flow regime and large-scale ascent will aid in scattered high-based, low-topped convection across WY this afternoon and spreading into western SD/NE this evening. With surface dew points only in the 20s to low 30s, buoyancy will likely remain scant. But inverted-v thermodynamic profiles will support a threat for sporadic severe wind gusts. $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .