Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Sat Apr 15 2023 08:54:00 ACUS01 KWNS 151231 SWODY1 SPC AC 151230 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0730 AM CDT Sat Apr 15 2023 Valid 151300Z - 161200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FROM SOUTHWEST IL/SOUTHEAST MO ACROSS AR TO NORTHERN LA... ....SUMMARY... Scattered large hail (some near or larger than 2.5" diameter), damaging gusts of 60-70 mph, and a couple of tornadoes are expected this afternoon/evening from southwest Illinois and southeast Missouri across Arkansas and northern Louisiana. ....Mid MS Valley to the Gulf coast through tonight... A midlevel trough now approaching the central Plains will continue eastward to the mid MS Valley by tonight. An initial surface cyclone will remain in WI today, with weak secondary cyclogenesis from central MO to northern IL today (along the rain-reinforced boundary now in central MO). To the south of the ongoing convection and outflow across MO, warm sector dewpoints range from the mid 60s in northeast OK to the upper 60s in northeast TX. This moisture will spread northeastward today across AR and southern MO, beneath a plume of steep midlevel lapse rates. The lapse rates and moisture, in combination with daytime heating, will drive MLCAPE of 2500-3000 J/kg, along with weakening convective inhibition. Thunderstorm development appears likely by mid afternoon from the northern fringe of the undisturbed warm sector in MO southwestward into western AR immediately ahead of the surface cold front. The moderate-strong buoyancy and relatively straight hodographs with effective bulk shear of 30-40 kt will favor a mix of supercells and clusters that will eventually grow into more of a linear configuration. Isolated very large hail (in excess of 2.5" diameter) will be possible with the initial, more discrete supercells, with a gradual transition to more of a wind damage threat as storms grow upscale into a line. Low-level shear will remain rather modest, though a couple of tornadoes may occur with the more persistent supercells and/or embedded circulations in the line. The line of storms is expected to weaken tonight while moving east of the MS River, in an environment with modest vertical shear and weakening buoyancy with eastward extent. Farther south, a small cluster of thunderstorms is moving across southeast TX. Notable low-level drying has been observed in the cold pool trailing this convection, which appears to be associated with a subtle southern stream shortwave trough. Exactly how this convection evolves today is a bit uncertain (along with the associated threats for hail/wind), though it appears probable that some form of the morning convection will develop eastward across southern LA along a warm front. If any upscale growth occurs during the day, this will tend to disrupt moisture return into MS. Isolated thunderstorm development may also occur late this afternoon along the cold front and remnant lee trough in TX. Deep-layer vertical shear will weaken with southwestward extent, but steep lapse rates and large CAPE will support some potential for large hail/damaging winds late this afternoon/evening. ...Thompson/Gleason.. 04/15/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .