Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jun 23 2025 19:57:58 ACUS01 KWNS 231956 SWODY1 SPC AC 231954 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0254 PM CDT Mon Jun 23 2025 Valid 232000Z - 241200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON THROUGH LATE EVENING FROM THE CENTRAL PLAINS TO THE UPPER GREAT LAKES... ....SUMMARY... Storms with occasional damaging outflow gusts and marginally severe hail will be possible today from the southern and central Plains northeastward into the Great Lakes. ....20z Update... Marginal hail and tornado probabilities were introduced across western Maine with this update. CAM guidance suggests supercells moving out of southern Quebec may track into western Maine. The moist and unstable environment across this region would be supportive of hail, wind, and perhaps a tornado as 850 mb flow increases through the evening. Otherwise, the forecast remains on track with no updates needed. See previous discussion for more information. ...Thornton.. 06/23/2025 ..PREV DISCUSSION... /ISSUED 1122 AM CDT Mon Jun 23 2025/ ....Upper Great Lakes to the Plains this afternoon/evening... A surface cold front will make slow southeastward progress from WI to IA and KS, in the wake of a primary shortwave trough moving over western ON. Surface heating is ongoing ahead of the front, where boundary-layer dewpoints range from the upper 60s to lower 70s beneath midlevel lapse rates of 7-8 C/km, which will drive MLCAPE of 2000-3000 J/kg. Convective inhibition will likewise weaken by early-mid afternoon, when thunderstorm development is likely along the front and differential heating zone in the SLGT risk corridor. Deep-layer flow will be a little stronger toward WI in closer proximity to the main belt of westerlies, where a mix clusters/line segments and transient supercell structures will be possible. The primary severe threat will be damaging outflow winds (60-70 mph) from roughly 20z-03z, though isolated large hail of 1-1.5 inches in diameter may also occur with the strongest storms. More loosely organized storm clusters are expected this afternoon through this evening into the southern High Plains, where thermodynamic profiles will favor isolated severe downbursts. ....Northern Maine later this evening... Around the northern periphery of a closed midlevel high over the Appalachians, a series of embedded speed maxima will move over ON/QC through tonight. Boundary-layer dewpoints in the 60s beneath midlevel lapse rates near 7 C/km, in combination with daytime heating, will boost MLCAPE to 1500-2000 J/kg with minimal convective inhibition by late afternoon. Thunderstorm development is expected upstream across QC in association with an embedded speed max/surface wave, and this convection will approach northern ME by late evening/early tonight. Though buoyancy will slowly weaken with the loss of daytime heating, low-level hodograph curvature and deep-layer westerly shear should be sufficient for an organized storm cluster to reach ME before weakening overnight. Isolated damaging winds will be the main threat with these storms. $$ = = = 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) .