SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1140 PM CST Wed Dec 01 2021 Valid 031200Z - 041200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk of severe thunderstorms appears negligible across the U.S. Friday through Friday night, but a low probability of thunderstorms may develop across parts of the southern Great Plains into Mid South. ...Discussion... Models continue to indicate significant amplification within a southern branch of split mid-latitude westerlies across the eastern Pacific during this period. This is forecast to include a vigorous short wave trough digging into the southern mid- and subtropical latitudes, between 140-160 W longitude. While a significant impulse within another branch progresses toward the British Columbia coast, it appears that strong downstream flow will remain broadly anticyclonic across the western Canadian/U.S. border vicinity into the northern U.S. Great Plains. However, mid/upper flow across the Great Lakes region is forecast to trend at least broadly cyclonic, in response to a significant perturbation digging southeast of the Canadian Prairies. Models indicate that this will be accompanied by much more modest surface cyclogenesis than the preceding short wave impulse, but more prominent cold surface ridging may build southeast of the northern Rockies, across much of the northern through central Great Plains and upper Mississippi Valley by 12Z Saturday. Meanwhile, a series of short wave perturbations is forecast to continue to develop eastward across parts of the Southwest into the Gulf Coast states, within a weak branch of westerlies emanating from the subtropical eastern Pacific. Across parts of the southern Great Plains into Mid South, elevated moisture return of subtropical Pacific origin likely will be coupled with moistening southerly return flow off the western Gulf of Mexico, ahead of the southward advancing cold front. ...Parts of southern Great Plains into Mid South... Models continue to indicate that boundary-layer moisture return from the Gulf of Mexico probably will remain confined to a rather shallow surface-based layer Friday through Friday night, beneath warm and capping layers aloft. However, forecast soundings still suggest that the elevated moisture return, in the presence of modestly steepening mid-level lapse rates, will contribute to weak CAPE based around the 700 mb layer. It appears that thermodynamic profiles may become conducive to occasional, widely scattered to scattered convection capable of producing lightning, aided mostly by weak mid/upper forcing for ascent. ..Kerr.. 12/02/2021 Read more LIVE: spc.noaa.gov
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