SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0208 AM CST Mon Dec 21 2020 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST TEXAS ACROSS THE CENTRAL GULF COAST INTO THE WESTERN FLORIDA PANHANDLE... ...SUMMARY... Isolated severe thunderstorms are possible from southeast Texas across the central Gulf Coast into the western Florida Panhandle. ...Synopsis... A deep surface low is forecast to be centered over east-central MN/northwest WI early Wednesday morning. A strong cold front will extend southwestward from the low across the Ozark Plateau and into north-central TX before arcing more westward through the TX Permian Basin. This front is expected to surge southward/southeastward throughout the day as the parent surface low moves eastward over the Upper Great Lakes and gradually occludes. At the same time, upper troughing initially extending from the Canadian Prairie Provinces into the central Rockies is expected to deepen significantly as it progresses eastward. Additionally, mid-level flow surrounding the trough will strengthen. By early Thursday morning, a large corridor of 100+kt 500-mb winds is expected to extend from the Lower MS Valley through the Upper Great Lakes into southeastern Ontario. Modest moisture advection associated with this system will likely result in low to mid 60s dewpoints from central/east TX into southern AL/MS and the FL Panhandle ahead of surging cold front. Widespread cloud cover will temper daytime heating and, along with poor lapse rates, will contribute to limited buoyancy. Even so, strong vertical shear supports organized storm structures with any mature/persistent updrafts. Based on current guidance, highest probability of severe storms appears to be across the western FL Panhandle early Thursday when the strengthening low-level flow aligns with the limited buoyancy. ..Mosier.. 12/21/2020
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