Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Aug 06 2025 20:00:23 ACUS01 KWNS 062000 SWODY1 SPC AC 061958 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Wed Aug 06 2025 Valid 062000Z - 071200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE CENTRAL/NORTHERN PLAINS TO THE UPPER MISSISSIPPI VALLEY AND MINNESOTA... ....SUMMARY... Isolated strong to severe thunderstorms are possible across parts of the northern/central Plains to the Mid-Mississippi Valley, and over part of northern Minnesota this afternoon and tonight. ....20z Update... The prior forecast remains largely on track with minimal changes. Current observations show stout capping in place over much of the central Plains. However, robust surface heating of a seasonably moist air mass (surface dewpoints upper 60s to low 70s F) is ongoing across parts of South Dakota and northern Nebraska. With continued heating this afternoon, gradual destabilization is expected to continue. Initial high-based convection should develop late this afternoon across eastern WY and western SD, and will gradually move eastward into moderate to large buoyancy. With 40 kt of mid-level flow also in place, there exists the potential for isolated supercells with hail and damaging gusts as the primary threats. The main uncertainty for higher severe probabilities today remains the nebulous forcing for ascent which should continue to favor sparse/isolated storm coverage into early evening. ....Eastern Plains and Missouri Valley to Midwest... Afternoon model guidance continues to show an increase in convection tonight associated with low-level warm air advection from the expected 30-40 kt low-level jet. The highest confidence in scattered storms is from the eastern half of SD/NE into parts of IA and southern MN late tonight. With steep mid-level lapse rates above a predominately stable boundary layer, hail and isolated damaging gust are possible. The MRGL risk was adjusted over southern NE to better match recent model guidance for higher storm coverage. Otherwise, the outlook remains unchanged. See the prior discussion for the previous discussion. ...Lyons.. 08/06/2025 ..PREV DISCUSSION... /ISSUED 1129 AM CDT Wed Aug 06 2025/ ....Northern/Central Plains into the Mid MS Valley... Water-vapor imagery late this morning shows a quasi-zonal flow regime from the northern Intermountain region east into the central Great Plains. A disturbance along the ND/Canadian border will continue east into the western ON vicinity late tonight. Weak mid-level height rises are forecast over the northern Great Plains downstream of a trough moving east into the northwestern CONUS from the eastern Pacific. A belt of stronger mid-level flow (i.e. around 40 kt at 500 mb) will extend across the region, and diurnal heating of the moist airmass in place will foster moderate to strong buoyancy. Forecast soundings show a vigorous combination of shear/buoyancy but nebulous forcing mechanisms suggest storm coverage later today/tonight will likely remain isolated/sparse. Little in the way of large-scale forcing for ascent will contribute to suppressing convective development through at least mid afternoon. Considerable uncertainty in storm development is apparent in convection-allowing models and some of these models show isolated storms perhaps favoring the greater Black Hills area. Will maintain a Marginal risk (level 1 of 5) despite favorable environmental conditions for supercells. Later tonight in association with low-level warm-air advection, a cluster or two of storms may evolve from the eastern half of SD/NE into the lower MO Valley/mid MS Valley. An isolated hail/wind threat could accompany this activity. ....Northern MN... A few storms may develop along the southern periphery of the Canadian Prairies shortwave upper trough and surface low. Lapse rates will be weaker across this area and the favorable thermodynamic environment will be narrow. Any stronger storms will likely remain close to the international border, but could produce locally strong gusts or marginal hail. $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .