Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 27 2025 07:29:37 ACUS03 KWNS 270729 SWODY3 SPC AC 270728 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Sun Jul 27 2025 Valid 291200Z - 301200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE NORTHERN ROCKIES...CENTRAL HIGH PLAINS...MID-MISSOURI VALLEY...MID-MISSISSIPPI VALLEY... ....SUMMARY... Severe thunderstorms are possible from southern Montana into the central High Plains as well as parts of the Mid-Missouri and Mid-Mississippi Valleys on Tuesday. ....Synopsis... Upper-level ridging will continue across much of the central and southern U.S. on Tuesday. A broad upper trough will strengthen in the upper Great Lakes and New England. Weak troughing will push into the West. A shortwave trough will move into the southern Great Basin. At the surface, moisture will remain near the northern/central Rockies. A modest cold front will be draped across the central Plains into the Lower Great Lakes. ....Southern South Dakota...Nebraska...Mid-Mississippi Valley... Similar to previous days, the forecast is uncertain and will depend upon how convection evolves on Monday night into Tuesday morning. Current guidance shows an MCS weakening Tuesday morning in the MN/IA/WI vicinity. Where outflow from this sets up during the afternoon will be a focus for potential storm development during the afternoon. Farther west, the surface low and cold front will have slid farther south. The exact position of this boundary is another point of uncertainty in the forecast. While the strong to extreme buoyancy south of the boundaries will be similar to Monday, the stronger shear is expected to remain just along and north of these boundaries. Forcing for ascent will also be less clear than on Monday as well. The most likely area for storm initiation will be where the surface low intersects the cold front in Nebraska. There is also some potential for clusters of storms that develop in eastern Wyoming to progress along the surface boundary into Nebraska as well. This environment could support MCS development given the quick upscale growth of any convective cluster and a modestly increasing low-level jet in the evening. There is potentially a corridor of greater severe risk, but it remains too uncertain highlight at this time. ....Montana/Wyoming into western South Dakota and the Nebraska Panhandle... Confidence in storm development is highest in these areas given the modestly moist airmass remaining pushed against the higher terrain. With a shortwave trough moving into the Great Basin, smaller perturbations can be expected to move into the central/northern Rockies. Widely scattered to scattered storms are possible during the afternoon. 30-40 kts of effective shear and moderately steep mid-level lapse rates, storms will be capable of severe wind gusts and isolated large hail. ....Parts of Lower Great Lakes/Ohio Valley... Given what could be a strong MCS/MCV moving out of the Upper Midwest Tuesday morning, some severe risk could develop ahead of this feature Tuesday afternoon. This is currently minimal support for this scenario in guidance. Confidence is low. Model trends will continue to be monitored. ...Wendt.. 07/27/2025 $$ = = = 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) .