SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1105 PM CST Wed Dec 02 2020 Valid 031200Z - 041200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms appears negligible across the U.S. today through tonight. ...Synopsis... Much of North America will remain under the influence of amplified, branching flow, downstream of a strong zonal jet across the western and central mid-latitude Pacific. Within this regime, positively tilted large-scale ridging appears likely to remain prominent across western portions of the U.S. and Canada. Downstream, models indicate that large-scale positively tilted troughing will continue to evolve across eastern Canada into the Upper Midwest, Great Lakes and Northeast. In lower-latitudes, increasingly deformed mid/upper troughing will be a prominent influence across parts of the Southwest and northern Mexican Plateau east-northeastward into the middle/lower Mississippi Valley. While an embedded mid-level low evolves south of the international border, across parts of Sonora and Chihuahua, another elongating embedded cyclonic circulation is forecast to continue slowly shifting eastward across the south central Great Plains into the Ozark Plateau. Generally dry and/or cold and stable conditions prevail across much of the U.S. Aside from some continued low-level moistening off a still recovering northwestern Gulf of Mexico boundary layer, little change is expected through this period. The moisture return will be focused along low-level troughing associated with the southern Great Plains perturbation, across the Louisiana coast into the Mid South. However, it appears likely to remain mostly elevated above at least a shallow residual near-surface stable layer, and, at least initially, beneath subsident and relatively warm mid/upper levels to the southeast of a weakening cyclonic mid-level jet strSevere thunderstorms are not forecast across the contiguous United States on Thursday.eak. ...Lower Mississippi Valley... Inland of coastal areas, model forecast soundings indicate thermodynamic profiles probably best characterized as only marginally conducive to convection capable of producing lightning today through tonight. Probabilities for thunderstorms appear generally low, but perhaps highest in a corridor from northeastern Louisiana into western and middle Tennessee late this afternoon into tonight. Occasional, scattered thunderstorm activity may become focused just to the cool side of the slowly eastward advancing cold front, perhaps aided by the onset of at least some cooling aloft. Otherwise, a cluster of thunderstorms now evolving across the northwestern Gulf of Mexico may persist into today, tending to develop eastward and southeastward, well south of the Louisiana coast. It appears that this activity may have a negative impact on convective potential near north central/northeastern Gulf coastal areas through much of the period. However, destabilization near a possible developing frontal wave might support increasing thunderstorm development near/east of Plaquemines Parish Louisiana into the vicinity of the western Florida Panhandle coastal waters by daybreak Friday. ..Kerr.. 12/03/2020
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