351 ACUS02 KWNS 161732 SWODY2 SPC AC 161730 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Wed Jun 16 2021 Valid 171200Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM IOWA INTO NORTHERN ILLINOIS AND SOUTHERN WISCONSIN... ...SUMMARY... Widely scattered strong to severe thunderstorms are possible mainly from Iowa into southern Wisconsin and northern Illinois Thursday and Thursday night. Large hail and damaging winds are possible with the stronger storms. ...Synopsis... A mid-level speed max over south-central Canada/North Dakota will gradually move southeastward into the Upper Midwest/western Great Lakes. A surface trough/front will extend roughly from southern MN into eastern NE during the mid afternoon and a warm front will advance east-northeastward across parts of the western Great Lakes. West to southwest low-level winds will maintain warm advection into the region, and will likely support bouts of severe storms beginning late afternoon across IA or southern MN, and eventually into IL overnight. ...Upper MS Valley/Great Lakes... Models are indicating the possibility for a few showers or storms to be ongoing Thursday morning anywhere from southern MN/western WI southward into northeast MO via theta-e advection. This early day activity will likely diminish by late morning with destabilization focusing near the surface trough. The strongest buoyancy is forecast across from eastern NE into IA, where heating and 65-70 deg F dewpoints will contribute to MLCAPE ranging from 4000+ J/kg near the MO River to 2500 J/kg in western WI. As convective inhibition weakens considerably by mid-late afternoon, isolated thunderstorms are forecast. Deep-layer shear will favor organized storms, including supercell potential during the afternoon-early evening. As large-scale ascent increases during the evening, upscale growth into a cluster will probably occur. There is uncertainty how far east/southeast the severe risk will develop Thursday night. Have left the convective outlook unchanged but additional adjustments to the severe probabilities will probably be needed. ...NE... The southwest portion of the surface boundary will become draped from west to east across NE on Thursday night. Strengthening warm-air advection coincident with a central Great Plains LLJ, may lead to isolated storms developing north of the surface boundary. It is unclear at this time whether this activity would pose an isolated risk for hail/wind---will defer this area to possibly being included in later outlook updates. ..Smith.. 06/16/2021 $$
