SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1028 AM CST Wed Feb 17 2021 Valid 171630Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTRAL GULF COAST... ...SUMMARY... Isolated to scattered damaging winds and a few tornadoes are possible across a portion of the central Gulf Coast, after about 6 PM CST through the overnight. ...Central Gulf Coast... No change has occurred with the cat 1 and 2 (MRGL and SLGT) risk areas. Primary mitigating concern for expansion or greater probabilities is the extent of surface-based warm sector inland within a very tight baroclinic zone. Surface cyclone over the northwest Gulf is progged to gradually fill as it approaches the western FL Panhandle through late tonight. Thunderstorms are expected to initially develop near this cyclone and then expand in coverage during late afternoon into tonight, primarily from elevated parcels north of the warm front. Initial linear organization for severe potential will probably commence just offshore of the south-central LA coast by late afternoon. This activity should eventually overlap with the impinging of low to mid 60s surface dew points into a portion of southeast LA during the evening. Here, rather enlarged low-level hodographs coincident with 50-60 kt effective shear should yield potential for embedded supercell structures within the squall line, capable of producing a few tornadoes and damaging winds. The very tight baroclinic zone will be characterized by an increasingly sharp low-level inversion with northern extent likely limiting the areal coverage of tornado and damaging wind potential farther inland (this region recently warming above freezing as of 16Z). Given the strength of the flow aloft, it is plausible that line segments may spread quickly northeast and outpace the surface-based warm-sector before it reaches the FL Panhandle overnight. The eastern portion of the tornado/wind risk (near the central portion of the FL Panhandle) between about 09-12Z may emanate from convection that can form in pre-frontal confluence bands across the northeast Gulf. ..Grams/Cook.. 02/17/2021
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