SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1137 PM CST Thu Dec 31 2020 Valid 011200Z - 021200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE SOUTHEASTERN STATES... ...SUMMARY... Thunderstorms may pose a modest risk for locally strong gusts and perhaps a tornado or two over a portion of the Southeast States today. ...Southeast States... Shortwave trough will be situated over eastern OK at the start of this period and this feature will continue northeast into southern IL by early evening. By 12Z a weak surface low will be located near Memphis with trailing cold front extending through eastern MS into the central Gulf. A warm front will extend east through northern MS and AL, north central GA and into southern SC. This low will track northeast and occlude across northern KY by early evening. The warm front will lift north into Middle TN today where surface dewpoints will reach the low 60s F, with mid to upper 60s with southward extent into the Gulf Coast states. Cold air damming across the western Carolinas will limit northward advance of the warm front in that region. Despite the moistening boundary layer, warm-sector instability will remain very marginal due to very weak lapse rates and widespread low clouds. Similar to Thursday, a significant limiting factor will result from lack of phasing between the deeper forcing attending the northeast-ejecting shortwave trough and the moist warm sector which will remain under the influence of an expansive mid-upper level dry slot. A band of convection including a few thunderstorms will likely be ongoing across a portion of western and middle TN. This activity will be embedded within favorable vertical shear profiles for severe storms including supercells, but updrafts will likely be at least slightly elevated above a stable near-surface layer. Farther east and south, additional thunderstorms will be ongoing along the conveyor belt from Middle TN southward through AL and the FL Panhandle. This activity will shift slowly east during the day. While some of this convection may become rooted in the boundary layer, especially with southward extent through AL, the impinging dry slot and very marginal thermodynamic environment will probably limit updraft and storm intensity despite strong vertical shear profiles. Nevertheless, some of this activity might produce a few instances of locally strong wind gusts and perhaps a tornado or two during the day. ..Dial/Squitieri.. 01/01/2021
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