Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Aug 11 2023 16:51:01 ACUS01 KWNS 111650 SWODY1 SPC AC 111649 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1149 AM CDT Fri Aug 11 2023 Valid 111630Z - 121200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR NORTHEAST KANSAS AND NORTHWEST MISSOURI... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR THE LOWER MISSOURI AND LOWER OHIO VALLEYS...UPPER MISSISSIPPI VALLEY...SOUTHERN GREAT LAKES...SOUTHERN GEORGIA INTO COASTAL SOUTH CAROLINA... ....SUMMARY... Scattered severe thunderstorms are forecast across the lower Missouri Valley late this afternoon through the evening. Supercells capable of very large hail, severe gusts, and perhaps a tornado are the primary threats. ....Central Great Plains east into the lower OH Valley... Complicated forecast scenario today with a small MCS moving southeast over south-central IL. It remains unclear whether a rejuvenation or strengthening of this complex will occur as the boundary layer continues to destabilize to its southeast across the lower Wabash Valley. Isolated damaging gusts appear to be the primary risk. Farther west, mid-level convection has been noted across parts of the central Great Plains late this morning. This is occurring on the northeast periphery of steep 700-500 mb lapse rates. Going forward this afternoon, models show a consensus in showing thunderstorms developing by mid afternoon from northern KS into northwest MO and perhaps southern IA where 3000+ J/kg of MLCAPE is forecast. Strengthening west-northwesterly flow with height will elongate hodographs and favor supercells. Large to very large hail and severe gusts will be the primary threats. A tornado is possible, especially where surface temperature-dewpoint spreads are near 20 deg F. Upscale growth is forecast this evening with a thunderstorm complex perhaps moving southeastward into the lower MO Valley overnight. Have reduced severe probabilities across parts of the IL in wake of the morning MCS where forcing mechanisms to initiate storms are nebulous and highly uncertain. ....Upper MS Valley... A mid-level speed max will approach the region this afternoon. Strong deep shear and weaker buoyancy are expected, but with instability still sufficient to support at least isolated strong-severe convection. MLCAPE 1000-2000 J/kg in parts of central/eastern MN and northern WI, under the strongest cooling aloft preceding the mid/upper trough. 40-50 kt effective-shear magnitudes are progged over the upper Mississippi Valley region as well. Large hail and damaging gusts are the primary risks with these storms. Some of this activity may move as far southeast as southern WI and northern IL late tonight. ....Southern Great Lakes... A disturbance moving east-southeast through the Great Lakes will probably aid in scattered thunderstorms developing this afternoon. Although heating will be tempered somewhat by a cirrus canopy this afternoon, model forecast soundings show moderate buoyancy (1000-2000 J/kg MLCAPE) amidst a veering and strengthening wind profile with height. Have added a small Slight Risk for the possibility for organized storms to pose a risk for damaging gusts, isolated large hail, and perhaps a tornado or two mainly late this afternoon through the early evening. ....Southeast states... Ongoing cluster of thunderstorms over the Savannah River Valley will continue to move east into the coastal plain of SC later this afternoon. Very moist low levels and temperatures warming into 90s south and east of early day storms will favor strong instability developing by early to mid afternoon. Water-loaded downdrafts will potentially yield strong and locally severe microbursts capable of wind damage. Have upgraded southern GA into southern coastal SC into a categorical Slight Risk where model guidance shows higher storm coverage and greater buoyancy (reference the 12z TLH raob) resides. This activity will likely diminish during the evening. ....Northwest TX/southwest OK... Intense heating will again promote temperatures warming well into the 100s deg F by late afternoon to near or at convective temperatures. Models indicate at least a few storms developing during the late afternoon/early evening. Very steep lapse rates will favor evaporative cooling and the potential for isolated severe gusts. ...Smith/Flournoy.. 08/11/2023 $$ = = = 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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .