ACUS01 KWNS 201219 SWODY1 SPC AC 201218 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0718 AM CDT Mon Jul 20 2026 Valid 201300Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE UPPER MIDWEST AND GREAT LAKES... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTH CAROLINA AND FAR SOUTHERN VIRGINIA... ...SUMMARY... Severe thunderstorms are expected across portions of the Upper Midwest and Great Lakes vicinity, especially late this afternoon and tonight. Swaths of damaging winds, large hail, and a few tornadoes will all be possible. Isolated damaging wind gusts may also occur over parts of the Carolinas and southern Virginia. ...Upper Midwest/Great Lakes... Radar/IR satellite composite this morning shows a decaying MCS over far northern IA into west-central WI with warm-advection-related storms moving east-southeast atop the MCS cold pool. This convective activity is occurring downstream of a seasonably potent mid-level shortwave trough and associated jet streak. Surface analysis this morning places a front over the mid MS Valley extending north-northwest and intersecting an outflow boundary over southwest MN. A surface low over western ON is forecast to develop east across north-central ON as an attendant cold front pushes southeast across the Upper Midwest. The front over the mid- to upper MS Valley will advance northeast as a warm front and the warm sector will become increasingly narrow with northward extent in the northern WI vicinity. A warm and seasonably moist airmass will advect northeast into WI in wake of the morning showers/thunderstorms, while a plume of elevated mixed-layer air overspreads the region from the west. Models generally show upper 60s to lower/middle 70s F surface dewpoints contributing to a very unstable boundary layer by mid-late afternoon. However, considerable uncertainty remains regarding details with this forecast update due in part to the morning convection and downstream destabilization/hazard specifics for later this afternoon/evening. It is plausible the initial storms that develop later this afternoon will quickly organize into supercells given strong deep-layer shear and ample buoyancy ahead of the cold front. In agreement with prior forecast thinking, a corridor of large hail and tornado risk will extend from Iowa across Wisconsin into Upper MI. Forecast soundings show elongated hodographs with 35-50 kt 700 mb flow, which will act to enlarge hodographs and perhaps support a couple of strong tornadoes. However, will defer any potential severe changes to later outlook updates if greater confidence and morning convective details are resolved. Eventually, a few clusters will probably evolve this evening, with a continued damaging wind and some tornado risk persisting southeastward before eventually waning overnight. ...Carolinas and southern Virginia... Strong heating to the south of a west-east oriented stalled front will contribute to moderate buoyancy by early to mid afternoon. Rich low-level moisture (surface dewpoints in the 70s F) and moist tropospheric profiles will yield high PW and the potential for water-loaded downdrafts with the more intense thunderstorm cores. Scattered thunderstorms with an isolated to scattered wind-damage threat will probably focus during the 18-00 UTC period. ...Florida... Tropical Depression Two is forecast to slowly intensify across the northeast Gulf of America today and tonight (refer to NHC's latest forecast details). Model guidance shows some gradual strengthening of 2-3km AGL flow, especially across the western Florida Peninsula. Yet, forecast soundings imply the possibility for transient supercell structures will likely be limited/low due to substantially weaker flow in the midlevels---precluding a low-severe highlight at this time. ..Smith/Broyles.. 07/20/2026 $$