Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 29 2025 19:56:01 ACUS01 KWNS 291955 SWODY1 SPC AC 291954 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0254 PM CDT Tue Jul 29 2025 Valid 292000Z - 301200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO TONIGHT FROM PARTS OF THE NORTHERN HIGH PLAINS INTO THE CENTRAL PLAINS... ....SUMMARY... Severe thunderstorms are expected from southern Montana into the central High Plains, and across much of Nebraska and western Iowa. Areas of severe gusts will be possible, with hail most likely over western areas. ....20z Update... The forecast largely remains on track with the early stages of convective initiation underway across portions of north/northwest WY and along the central High Plains per recent satellite imagery and regional radar composites. The primary change for this forecast update was the introduction of significant hail/wind areas to portions of the northern Rockies. Latest GOES imagery shows convection beginning to develop across northern WY/southern MT ahead of a shortwave trough over the Great Basin. Regional 18z soundings continue to sample steep (8-9 C/km) mid-level lapse rates, and GOES imagery suggests 30-40 knot mid-level winds are overspreading the region. As such, a favorable environment for a few supercells appears to be in place and should support the potential for very large hail. This activity should grow upscale through late evening with the potential for a few significant (75+ mph) wind gusts. See MCD #1833 for additional short-term details. Across the Plains, the significant wind risk area has been adjusted to better align with recent convective development along a stationary boundary draped from southwest to northeast across NE and where boundary-layer mixing appears to be deepest (based on observed dewpoint depressions), which should favor stronger downdrafts and a higher potential for significant gusts. See MCD #1834 for additional short-term details. ...Moore.. 07/29/2025 ..PREV DISCUSSION... /ISSUED 1132 AM CDT Tue Jul 29 2025/ ....CO/NE/IA... Surface analysis indicates a frontal zone draped from IA west-southwestward into the central High Plains. Moist conditions either side of the boundary and ample heating will promote a very to extremely unstable airmass as temperatures continue to warm through the mid afternoon. Initial storms are progged over the central High Plains with perhaps other activity continuing across the mid MS Valley through the afternoon. Hail/wind will be possible with the earlier storms, but a gradual increase in storm coverage is forecast this evening into the overnight near/north of the boundary. Severe gusts will tend to be the main severe hazard tonight. ....WY/MT... Water-vapor imagery late this morning shows a prominent shortwave trough over the northern Great Basin moving into eastern ID/WY this afternoon. A moist (dewpoints in the 50s to lower 60s) and destabilizing boundary layer near/northeast of a residual frontal zone, coupled with orographic and large-scale ascent, will lead to scattered afternoon thunderstorms. Easterly flow beneath moderate westerlies will yield effective shear supporting organized storms, including a few supercells and organized clusters. Hail/wind will be the primary severe hazards before a tendency for upscale growth into linear clusters during the evening. ....Southeast OR... A mid-level trough over the Sierra into the northern Great Basin, embedded within larger-scale trough over the West Coast, will move northward through this evening across the northern Great Basin into southern OR/ID. Scattered high-based thunderstorms will probably focus along the leading edge of ascent as low to mid tropospheric lapse rates exceed 9 deg C/km. A relatively dry sub-cloud layer will promote evaporatively cooled downdrafts capable of isolated severe gusts (60-70 mph) with the stronger cores/clusters, mainly during the 22-04 UTC period. $$ = = = 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) .