SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0733 AM CDT Wed Sep 16 2020 Valid 161300Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE FLORIDA PANHANDLE...NORTHWESTERN FLORIDA...SOUTHEASTERN ALABAMA...AND SOUTHERN GEORGIA... ...SUMMARY... As Hurricane Sally moves further inland, it may produce a few tornadoes over parts of the Florida Panhandle, northwestern Florida, southeastern Alabama, and southern Georgia through tomorrow morning. ...Synopsis... In mid/upper levels, an elongated cyclone over the northeast Pacific will move slowly eastward, causing height falls across parts of the Pacific Northwest. Downstream, and past a prominent upper ridge over the northern Rockies, the northern-stream cyclonic-flow field across the Great Lakes and vicinity will amplify with height falls. This will occur as a strong cyclone digs southeastward across Hudson Bay. Meanwhile, a weak but extensive area of troughing will move slowly southeastward across the Mid-South, southern Plains and northern MX. These processes will encourage recurvature of what now is Hurricane Sally northeastward across AL toward western GA through the period, per NHC forecast. See NHC advisories for the latest track/intensity guidance on Sally as the cyclone proceeds deeper inland. ...Southeast... See SPC tornado watch 491 and related mesoscale discussions for near-term tornado threat with Hurricane Sally. The center of this hurricane made landfall near Gulf Shores, AL, around 1045Z, and is forecast by NHC to turn northeastward and accelerate (while still moving slowly) across southern AL. As that occurs, a favorable sector of the eastern semicircle -- south of a persistent/stabilizing precip shield -- will spread/ expand inland and also eastward, in step with that component of Sally's translational vector. Some expansion of the supercell- supporting wind fields just above the surface also is possible tonight as inland decay of the strongest core winds proceeds, with system-relative radial spread of enlarged low-level shear/hodographs into more of the eastern semicircle, and across southern GA and perhaps northwestern FL. Rich inflow-layer moisture and low LCLs are a given. The main limiting factor will be buoyancy, though with sustained favorable inflow off the Gulf amidst a more-southerly surface wind component, advecting greater theta-e inland across the FL Panhandle/I-10 corridor today and into portions of southern GA from late afternoon onward. ..Edwards/Broyles.. 09/16/2020
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