SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1250 AM CDT Sun Oct 18 2020 Valid 181200Z - 191200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected across the country. ...Eastern OK to Southern IN... Broad mid-level cyclonic flow is forecast to continue across the northern two-thirds of the CONUS during the day1 period. Within this flow regime, several notable short-wave troughs are expected to translate across the northern tier of States before ejecting through the Great Lakes. As a result, the primary corridor for meaningful large-scale forcing for ascent should be noted ahead of these features. The main area where convection seems likely will be across the Ozark Plateau region into the lower OH Valley. While the aforementioned storm track will be just north of this corridor, veered LLJ from north TX into KY should aid moistening atop the boundary layer within a warm-advection regime. Latest model guidance continues to suggest buoyancy will increase from northeast TX-AR-lower OH Valley, but a notable warm layer near 700mb, and marginally steep mid-level lapse rates, should limit instability. Forecast soundings suggest MUCAPE between 500-800 J/kg will be common where elevated convection is expected to develop, primarily during the latter half of the period. Local hail algorithms suggest any hail that generates within this convection should be mostly sub-severe. For these reasons have lowered the severe threat to less than 5 percent. ...South FL... Deep easterly flow along the southern periphery of an elongated upper ridge will maintain moist profiles across south FL. Forecast soundings exhibit high-PW air mass with poor lapse rates, but modest flow for westward-moving convection. Latest satellite imagery/model data suggest a weak mid-level disturbance will approach the FL Atlantic coast later this morning. This feature should encourage scattered convection that will track west toward the Gulf Coast during the afternoon. ..Darrow/Lyons.. 10/18/2020
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