SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0138 PM CST Sun Jan 31 2021 Valid 312000Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS SOUTH GEORGIA INTO NORTH AND WEST FLORIDA THIS EVENING THROUGH TONIGHT... ...SUMMARY... A brief tornado and locally damaging winds are possible this evening into tonight across parts of south Georgia into north and west Florida. ...20z Update - FL/GA... The previous forecast remains on track and no changes have been made with this update. Low-to-mid 60s surface dewpoints have spread northeast across northwest FL into southern GA this afternoon. This is aiding in weak destabilization ahead of deeper convection now developing along the front from southwest GA into southeast AL. This activity is expected to slowly increase toward evening as the front approaches the Marginal risk area. Short-term CAMs and forecast soundings continue to indicate and environment capable of supporting low-end supercells, an a couple of strong-to-severe storms are still expected. For more details, see previous outlook below. ..Leitman.. 01/31/2021 .PREV DISCUSSION... /ISSUED 1015 AM CST Sun Jan 31 2021/ ...FL/GA... A shortwave trough centered over the Midwest will amplify on approach to the central and southern Appalachians as a mid-level speed max over the south-central states ejects through the basal portion of the trough across the Southeast. In response, an initial surface cyclone will slowly decay across the OH Valley while secondary cyclogenesis occurs across the Southeast and more prominently off the NC/VA coast towards 12Z Monday. A cold front will move southeast and reach southwest GA to the eastern FL Panhandle by 00Z before progressing off most of the South Atlantic coast and north/central FL tonight. Low-level moisture return will likely remain characterized by 62-64 F surface dew points across the north-central to northeast Gulf coast regions. More pronounced boundary-layer heating is expected to be confined east of the moisture plume across north and central FL. The net result will be the presence of weak buoyancy given relatively poor mid-level lapse rates. By this evening, modest cooling aloft and strengthening convergence near the front should support isolated thunderstorms from the FL Big Bend into south GA. The combination of adequately enlarged low-level hodographs (amid strong southwesterly deep-layer shear) and the limited buoyancy may be sufficient for a couple lower-end supercells as convection increases in coverage across north FL to the west coast of the peninsula. Strengthening 700-mb winds may also foster a short-line segment or two with a risk for locally damaging winds from strong gusts along the northern periphery of scant surface-based buoyancy into south GA. While it is plausible that severe storms may not develop at all, enough signal exists to warrant a cat 1/MRGL risk delineation.
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