SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0132 AM CST Sun Dec 13 2020 Valid 151200Z - 161200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for thunderstorms appears negligible across the U.S., Tuesday through Tuesday night. ...Discussion... Models indicate that initially amplified mid/upper troughing digging to the lee of the southern Rockies by 12Z Tuesday may undergo considerable shearing during this period. The primary embedded short wave perturbation, perhaps including at least a transient closed mid-level low, is generally forecast to pivot across the central and southern Great Plains, through the middle and lower Mississippi Valley by the end of the period. As it does, it is forecast to provide support for slowly deepening surface troughing across and east of the Mississippi Valley. Although initially expansive cold surface ridging across and east of this region at the outset of the period will suppress significant surface cyclogenesis, this may include the development of a surface low over the lower Ohio Valley by 12Z Wednesday. Otherwise, a frontal zone, initially extending across the central Florida Peninsula into the northern Gulf of Mexico, probably will become the primary focus for potential cyclogenesis. And models indicate a couple of waves developing along it by late Tuesday night. Boundary-layer moistening and destabilization within the warm sector of one of these, across the north central into northeastern Gulf of Mexico, could provide support for increasing thunderstorm activity (well offshore) Tuesday night. Another wave, developing a bit later, may be accompanied by at least increasing boundary-layer destabilization off the south Atlantic coast. Otherwise, across and inland of coastal areas, through most of the U.S., generally stable conditions are likely to prevail with negligible risk for thunderstorms. ..Kerr.. 12/13/2020
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