Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 13 2025 05:39:34 ACUS01 KWNS 130538 SWODY1 SPC AC 130537 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1237 AM CDT Fri Jun 13 2025 Valid 131200Z - 141200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF MONTANA... ....SUMMARY... Scattered severe thunderstorms are expected across much of Montana, extending south across the central High Plains. The greatest concentration of severe is expected across Montana where very large hail, and severe winds are anticipated. ....Montana, south into the central High Plains... 500mb speed max (50+kt) is forecast to translate across southern OR into the northern Rockies by late afternoon as a short-wave trough advances inland. At the surface, southeasterly low-level flow is expected to be maintained across much of MT east of the higher terrain, and moist boundary-layer conditions will be drawn deep into the mountains prior to convective initiation. Early this morning, lower-mid 50s surface dew points were observed as far west as Helena and Polson. Latest model guidance suggests CINH will be negligible by 18z across the higher terrain, and convection should readily develop within an increasingly sheared and modestly buoyant environment. NAM sounding for C18 at 18z exhibits 65kt 0-6km bulk shear, with 8 C/km lapse rates, and 1300 J/kg SBCAPE. Hodographs favor very large hail with these conditions and 2+ inch stones are certainly possible with the more robust supercells. Scattered supercells should develop by early afternoon then spread east and mature as they advance toward central/southern MT. Some tornado threat can be expected with these storms as ample low-level shear should be present. With time multiple thunderstorm clusters could emerge and severe winds may become more common as this activity propagates toward southern MT. Farther south across the High Plains of eastern WY into western KS, more isolated activity is expected within a weaker flow regime. 00z model guidance suggests a surface boundary will be draped across this region, extending southeast into central OK. This boundary will likely serve as the focus for diurnally enhanced convection. Forecast soundings suggest strong SBCAPE will be noted across the central High Plains into central OK where values should exceed 3000-4000 J/kg at lower latitudes. Somewhat stronger northwesterly flow will extend across eastern OK into western AR and this may result in some organizational potential along the backside of the MS Valley trough. Have extended severe probs across OK into western AR to account for this possibility. ...Darrow/Supinie.. 06/13/2025 $$ = = = 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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .