SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 AM CDT Tue Aug 15 2023 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE UPPER MIDWEST... ...SUMMARY... Strong to severe thunderstorms are expected across portions of the Upper Midwest Wednesday evening. ...Synopsis... A strong shortwave trough is forecast to progress across the Canadian Prairie Provinces into western Ontario and adjacent portions of the Upper Midwest and Upper Great Lakes on Wednesday. Strong mid-level flow will accompany this shortwave trough, with 50 to 70 kt of 500-mb flow spreading across MN by late Wednesday afternoon/early evening, and across WI and the Upper Great Lakes by early Thursday morning. Surface low associated with this system will stay north of the international border, but an attendant cold front is expected to sweep quickly southeastward across the northern Plains and Upper Midwest. Elsewhere, upper ridging is expected to build northward from the Southwest through the Great Basin and into the eastern Pacific Northwest. Numerous thunderstorms are expected in the Four Corners vicinity, where mid-level moisture will remain in place beneath this upper ridging. Weak vertical shear will limit the severe-thunderstorm potential in this area. Thunderstorms are also expected from NC southward into FL, where a moist airmass will remain in place ahead of a stalled front. Weak vertical shear should limit the severe-thunderstorm potential. ...Upper Midwest... Cold front mentioned in the synopsis will likely extend from northwestern Ontario southwestward through northwest MN and eastern ND into central SD at 18Z. By 00Z, this front is expected to extend from the MN Arrowhead southwestward through the SD/MN/NE border vicinity and into central NE. Mid to upper 60s dewpoints should be in place ahead of this front across MN. Strong diurnal heating is also expected ahead of this front, but warm and dry southwesterly low-level flow could prevent the airmass from fully destabilizing. As a result, some guidance keeps significant convective inhibition in place from the mid MO Valley into southern MN. Given these conditions, thunderstorm development appears most likely to begin along the front across northern MN around 18Z. Development should then gradually build southward as the front continues eastward. Given the forcing along the front, a predominantly linear mode appears most likely, with robust wind fields contributing to a risk for strong gusts. Hail also appears possible, particularly with any early, more cellular development. Elevated storm development may also occur behind the front, with some hail possible in this activity as well. ..Mosier.. 08/15/2023
