SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0700 AM CST Wed Nov 25 2020 Valid 251300Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER MISSISSIPPI VALLEY/TENNESSEE VALLEY INTO THE OHIO VALLEY... ...SUMMARY... Isolated strong to severe thunderstorms are possible today from the lower Mississippi Valley into the Tennessee Valley and lower Ohio Valley. Locally damaging winds should be the main threat, although a tornado or two could also occur. ...Lower Ohio Valley/Tennessee Valley/Lower Mississippi Valley... A shortwave trough/speed max aloft over the Ozarks will steadily progress east-northeastward today and tonight over the Ohio and Tennessee Valleys, with a corresponding surface wave moving northeast across Missouri/Illinois/Indiana and Ohio through evening. Ahead of an eastward-moving cold front, showers are prevalent early this morning across the lower Ohio Valley and western Tennessee, with thunderstorms associated with a semi-organized convective line across Mississippi into central/southern Louisiana. Initially, an isolated severe risk should persist early today with the aforementioned convective line as it continues across Mississippi/southern Louisiana into Alabama, with damaging winds a possibility along with a quasi-linear-related localized tornado risk. Other strong/locally severe low-topped thunderstorms could develop this afternoon near the surface low, including far eastern portions of Missouri/western Kentucky and southern Illinois. However, the degree and likelihood of such a severe risk is not certain given a relatively limited opportunity/potential for destabilization, but a damaging wind/localized tornado risk could occur. Farther south, in the wake of the early day convection, there are some indications that storms could redevelop near the cold front late this afternoon and evening across the Tennessee Valley including northern Alabama and possibly nearby portions of middle Tennessee and/or eastern Mississippi. It is possible if not probable that guidance such as the RAP/NAM are too quick/aggressive with air mass recovery and destabilization into late afternoon/early evening. However, should modest/adequate destabilization occur, given that the region would be within the entrance region of a strong south-southwesterly low-level jet, wind profiles would be favorable supercells potentially including some tornado/damaging wind risk. Portions of this region could warrant a categorical Slight Risk upgrade if confidence increases in air mass destabilization in the wake of early day convection/cloud cover. ..Guyer/Broyles.. 11/25/2020
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