SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Wed Aug 09 2023 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE MID MS VALLEY AND UPPER MIDWEST... ...SUMMARY... Severe thunderstorms capable of large hail, damaging gusts, and perhaps a tornado or two are possible across portions of the Middle Mississippi Valley and Upper Midwest on Friday. ...Synopsis and Discussion... Upper ridging is expected to build across the southern Plains and Southwest on Friday, as a pair of shortwave troughs traverse the belt of enhanced flow north of this ridging from the northern Plains into the Northeast. Lead shortwave is expected to move quickly through northern New England early in the period, while the westernmost shortwave drops from the Canadian Prairie Provinces through the Upper Midwest and Upper Great Lakes. Upper 60s to low 70s dewpoints will likely precede this shortwave trough and associated surface low/cold front. Strong diurnal heating will combine with this low-level moisture to support moderate to strong buoyancy from KS into the Upper Midwest by Friday afternoon. Strengthening mid-level flow will also accompany this shortwave, with 50+ kt at 500-mb spreading into the Upper Midwest. However, these favorable conditions will be countered by veered low-level flow limiting convergence along the front, and relatively warm low/mid-level temperatures and associated convective inhibition. Even with these limiting factors, severe thunderstorms are still expected from the central Plains into the Upper Midwest/Upper Great Lakes Friday afternoon through Friday evening. Highest coverage is currently expected to be from northeast MO/southeastern IA across northern IL into southern WI where convective inhibition will likely be weakest. The moderate to strong vertical shear in place will support updraft organization, with large hail and damaging gusts possible with the more robust/mature cells. There will also likely be enough low-level shear to support a low-probability tornado threat. Numerous thunderstorms are also expected in the vicinity of a weak frontal boundary draped across the Southeast states. Limited deep-layer shear should keep the organized thunderstorm potential minimal. ..Mosier.. 08/09/2023
