Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Aug 29 2024 05:46:42 ACUS01 KWNS 290546 SWODY1 SPC AC 290545 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1245 AM CDT Thu Aug 29 2024 Valid 291200Z - 301200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER/MIDDLE MISSISSIPPI VALLEY... ....SUMMARY... Severe thunderstorms are expected across the Upper/Middle Mississippi Valley to the central Plains. A few severe storms also will be possible over portions of the mid-Atlantic region. ....Upper/Middle Mississippi Valley... Southern portions of a strong upper trough, currently located over the northern Rockies, will eject across the Dakotas this afternoon. As 70-80kt 500mb speed max translates through the base of the trough across ND, primary upper low will track across southern AB into northwestern ON during the latter half of the period. Latest model guidance suggests very strong 12hr mid-level height falls just north of the international border, with more modest falls into the upper Mississippi Valley by 29/00z. Strong low-level warm advection will likely prove instrumental in one or more thunderstorm clusters over eastern ND/northwestern MN at the start of the period. LLJ responsible for this activity will shift into northwestern ON during the day, and this warm-advection activity should lift north of the border as well. However, strong boundary-layer heating will occur across eastern NE into extreme southwest MN by early afternoon. This will aid instability, and CINH will begin to weaken along the front, as surface temperatures rise into the mid 80s across central MN. NAM forecast sounding for KLJF at 22z is thermodynamically impressive with MLCAPE around 5400 J/kg and 0-6km shear approaching 30kt. 30-35kt deep-layer shear is expected along the northern extent of the stronger buoyancy. As a result, supercells are expected to develop along/ahead of the cold front, supported aloft by the upstream short wave. Large hail, severe gusts, and a few tornadoes are the expected hazards with these storms. Scattered convection, with a more-isolated severe threat, is forecast along the trailing cold front across the central Plains as readings breach convective temperatures later in the afternoon. Wind profiles at lower latitudes are not very strong, so this activity will be multicellular and less organized. Even so, some risk for hail/wind can be expected into the evening hours. ....Middle Atlantic Region... Dominant surface anticyclone over southeastern Canada will shift across ON/QC, which will allow a synoptic front to drape itself across the Middle Atlantic during the afternoon. This boundary will focus scattered thunderstorms as convective temperatures are breached by mid afternoon. Wind profiles favor mostly disorganized pulse-multicell updrafts. These storms will move slowly southeast with an attendant risk for wind and perhaps some hail. Robust updrafts will be strongly diurnally driven. ...Darrow/Jirak.. 08/29/2024 $$ = = = 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) .