SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0140 AM CDT Fri Oct 02 2020 Valid 041200Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms appears negligible across the U.S. Sunday through Sunday night. ...Discussion... Mid/upper flow across much of North America appears likely to continue to trend less amplified; but, models indicate that large-scale ridging will persist across the eastern mid-latitude Pacific into western North America, with large-scale troughing east of the Rockies through the Atlantic Seaboard. Embedded within this regime, there may be several short wave perturbations comprising more substantive troughing across the Upper Midwest into the lower Missouri Valley at the outset of the period. This is forecast to remain progressive, as a vigorous upstream short wave impulse digs across the Canadian Prairies. However, models indicate that the smaller-scale perturbations may trend out of phase. The southern portion of the remnant troughing may become most prominent, with perhaps the most vigorous impulse pivoting across parts of the Ohio/Tennessee Valleys into the southern Appalachians Sunday through Sunday night. A reinforcing low-level cool intrusion and subsidence in the wake of the lead mid-level troughing probably will contribute to diminishment of initially low convective potential over the interior U.S. Sunday. There could still be some lingering risk for convection capable of producing lightning, beneath the mid-level cold pool across parts of the Great Lakes and Ohio Valley into the Appalachians. However, model spread concerning the smaller-scale mid-level perturbations is sizable. Coupled with the weak nature of the potential instability, and probable sparse thunderstorm coverage, any risk for thunderstorms at this point still seems less than 10 percent. Otherwise, seasonably moist conditions likely will remain confined to a narrow plume along a remnant frontal zone across the southeastern Gulf of Mexico into areas near/east of the southern Mid Atlantic coast. This may contribute to at least low probabilities for thunderstorms across parts of the Florida Peninsula; but, models indicate that substantive boundary-layer moisture and instability will remain confined to areas near and east of the southeastern/eastern Florida Atlantic coast. ..Kerr.. 10/02/2020
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