Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 27 2025 01:04:02 ACUS01 KWNS 270104 SWODY1 SPC AC 270102 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0802 PM CDT Sat Jul 26 2025 Valid 270100Z - 271200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTH-CENTRAL U.S.... ....SUMMARY... Severe thunderstorms with damaging wind gusts and hail will be possible this evening into tonight across parts of the northern Plains from eastern Montana into the Dakotas and southward to Nebraska. Isolated damaging wind gusts will also be possible this evening from parts of the mid Mississippi Valley eastward into the Mid-Atlantic. ....Central and Northern Plains/Northern Rockies... At mid-levels, a ridge will remain located over the northern Plains this evening, as a shortwave trough approaches from the southwest. The shortwave is moving northeastward across the central and northern Rockies, which is evident on water vapor imagery. Ahead of this feature, large-scale ascent will overspread a moist airmass located across the central and northern Plains. Surface dewpoints within this airmass are mostly from the mid 60s to mid 70s F. This is contributing to a large pocket of strong instability across the Dakotas, where MLCAPE is estimated to be in the 3500 to 5500 J/kg range, according to RAP analysis data. Moderate instability extends southward into the central Plains. Along the western edge of the stronger instability, a broken line of thunderstorms is ongoing from central South Dakota southward into western Nebraska. Moderate deep-layer shear is analyzed by the RAP over much central and northern Plains. The stronger flow is a result of upper-level jets located over far southern Canada and central Nebraska. RAP forecast soundings from western Nebraska northward into the central Dakotas generally show 0-6 km shear in the 30 to 40 knot range, with directional shear located in the low to mid-levels. This will be favorable for supercell development this evening, mainly with cells that remain semi-discrete. Supercells will likely have an isolated large hail threat, mainly from central South Dakota into southern and eastern North Dakota, where the strongest instability is located. Hailstones greater than 2 inches in diameter will be possible. In addition, organized line segments with wind-damage potential are expected. Further west into parts of the northern High Plains, scattered thunderstorms are ongoing across central and northeast Montana. As the shortwave trough moves across the region this evening, convective coverage is expected to gradually increase. A severe threat will be possible along an near an axis of moderate instability, which the RAP currently shows from northwestern North Dakota into north-central Montana. Very steep low to mid-level lapse rates would be favorable for damaging wind gusts with the stronger storms. .....Mid Mississippi and Ohio Valleys/Central Appalachians/Mid-Atlantic... A mid-level trough is currently evident on water vapor imagery over the central and southern Great Lakes. Scattered thunderstorms are ongoing along the southern edge of this feature from the mid Mississippi Valley eastward into the central Appalachians. Along this east-to-west corridor, surface dewpoints are from the 70s into the lower 80s F. This is contributing to moderate instability, which is present over most of the region. The unstable environment should support a marginal wind-damage threat associated with the stronger multicells this evening. ...Broyles.. 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) .