SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0219 AM CDT Tue Jul 27 2021 Valid 291200Z - 301200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE LOWER MISSOURI VALLEY...MID MISSISSIPPI VALLEY...OHIO VALLEY...CENTRAL APPALACHIANS...CENTRAL HIGH PLAINS AND CENTRAL ROCKIES... ...SUMMARY... A marginal severe threat will be possible on Thursday from parts of the lower Missouri Valley eastward into the central Appalachians. A marginal severe threat will also be possible in parts of the central High Plains and central Rockies. ...Lower Missouri Valley/Mid Mississippi Valley/Ohio Valley/Central Appalachians... A large area of high pressure will remain in place on Thursday from the western U.S. southeastward into the lower Mississippi Valley. At the surface, a cold front is forecast to advance southward across the central U.S. The front should be positioned from northern Missouri eastward to the Ohio Valley by midday. As surface temperatures warm, moderate to strong instability will likely develop along and to the south of the front. Convective initiation is forecast near the front during the afternoon, with thunderstorms developing and moving south-southeastward across the region. The instability combined with moderate deep-layer shear evident on forecast soundings will be favorable for a marginal severe threat. The stronger thunderstorms may be capable of producing isolated wind damage during the late afternoon and early evening, mainly in areas where low-level lapse rates become very steep. An upgrade to slight risk may become necessary across parts of the lower Ohio Valley if the models show run-to-run consistency over the next day or so. ...Central High Plains... A large area of high pressure will remain across the western and south-central U.S. on Thursday, as a cold front moves southward across the central Plains. A corridor of moderate instability oriented from west-northwest to east-southeast will likely be in place by afternoon. Scattered convection is forecast to initiate in the higher terrain of southeast Wyoming and northeastern Colorado during the afternoon. Other more isolated storms could initiate further to the east near the front across southern Nebraska. Model forecasts across the central High Plains suggest that deep-layer shear will be strong enough for a marginal wind-damage threat. The wind-damage threat will likely be the greatest along the leading edge of short line segments. Hail could also occur with cells that rotate in areas where instability becomes the strongest. ..Broyles.. 07/27/2021
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