SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1132 PM CST Wed Jan 06 2021 Valid 071200Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR AREAS SOUTH OF THE MISSISSIPPI...ALABAMA...FLORIDA PANHANDLE COASTS AND THE WESTERN FLORIDA COAST... ...SUMMARY... A very low/conditional threat for a damaging gust or brief tornado exists across the mouth of the Mississippi eastward to just south of the Florida Panhandle coast during the day, and the western Florida Peninsula tonight. ...Synopsis... A mid-level trough will traverse the Southeast states, with a 75 kt 500 mb jet overspreading the Florida Panhandle through the period. A surface low will also progress across the Deep South. A 35+ kt 850 mb jet will encourage modest warm air advection and marginal elevated buoyancy to move inland and promote some lightning flash potential. However, with the latest guidance depicting more surface based instability struggling to move ashore, severe potential will likely be limited to areas immediately offshore. However, as a cold front approaches the western coast of the Florida Peninsula during the late evening (after 03Z), some surface-based instability may advect inland ahead of a confluence band, where more organized thunderstorm potential will exist. Elsewhere across the CONUS, A mid-level trough, accompanied by deep-layer ascent and very modest buoyancy may encourage a couple lightning flashes across portions of the Pacific Northwest shoreline. ...Portions of Florida today into tonight... The surface cold front and an associated arcing band of low-topped convection are expected to be positioned across the mouth of the Mississippi at the start of the period (12Z). While the 40+ kt southerly low-level jet, bisected by the stronger westerly mid-level flow, will result in ample deep-layer shear for storm organization, surface-based instability (500 J/kg MLCAPE at best) is expected to remain well offshore, as will the risk for a damaging gust or tornado. As such, a Marginal risk has been maintained south of the Gulf shoreline. By late evening, low 60s F dewpoints are expected to advect inland along the western Florida coastline, contributing up to 500 J/kg MLCAPE in spots despite poor low and mid-level lapse rates. Modest veering in the sfc-850 mb layer ahead of the cold front suggests that any of the more sustained storms may acquire brief instances of rotation. As such, a Marginal risk has been introduced for the possibility of a damaging gust or perhaps a brief tornado. However, buoyancy quickly deteriorates with eastward extent, and storms are expected to gradually weaken after 06Z per latest CAM guidance consensus. ..Squitieri/Darrow.. 01/07/2021
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