SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 PM CDT Wed Jul 11 2018 Valid 120100Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING INTO THE OVERNIGHT HOURS ACROSS PARTS OF NORTHERN AND CENTRAL MINNESOTA AND ADJACENT PORTIONS OF THE PLAINS/UPPER MIDWEST... ...SUMMARY... Strong to severe thunderstorm development remains possible this evening into the overnight hours across parts of the upper Mississippi Valley and northern Plains. ...01Z Outlook Update... Seasonably high boundary layer moisture content is contributing to moderate to strong potential instability within a corridor across central Iowa through western/central Minnesota, and along ahead of a surface cold front now advancing southeastward through the Dakotas. However, stronger mid-level height falls and 2-hour surface pressure falls associated with a vigorous short wave trough and associated cyclone are focused north of the international border, across Manitoba, and are generally forecast to develop eastward into northwestern Ontario overnight. Forcing for ascent to overcome inhibition and support appreciable convective development south of the international border remains unclear, but model output continues to generally suggest that this will eventually occur. It is possible that an area of enhanced lower/mid tropospheric warm advection, which now appears to be present across northeastern South Dakota/southeastern North Dakota into west central Minnesota, may provide the primary focus/forcing for thunderstorms while developing eastward through the 03-06Z time frame. Given the degree of potential instability, and at least marginally sufficient shear for organized convection, the environment appears conducive to the evolution of an upscale growing convective system given thunderstorm initiation. If this occurs, activity is expected to tend to gradually propagate southeastward. Otherwise, at least attempts at thunderstorm initiation are ongoing ahead of the cold front across areas to the west/north of Bemidji MN. Although near surface flow may gradually veer from an easterly/southeasterly component to a south/southwesterly component by daybreak, cold/cool and stable boundary layer air is expected to remain prominent near the western shores of Lake Superior and tend to suppress severe weather potential across that area. To the west/southwest, across central South Dakota into the Black Hills region, the front may become a focus for thunderstorm development overnight (after 06Z) as it stalls ahead of an area of developing mid-level height falls associated with a perturbation emerging from the Wyoming Rockies. If this occurs, thermodynamic profiles may be supportive of thunderstorms capable of producing widely scattered strong surface gusts. ..Kerr.. 07/12/2018
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