SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1100 PM CST Mon Feb 22 2021 Valid 241200Z - 251200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Aside from a small portion of the Colorado Plateau into adjacent upper Rio Grande River vicinity, the risk for thunderstorms appears negligible across much of the U.S., Wednesday through Wednesday night. ...Discussion... In the wake of a vigorous short wave impulse progressing around its northeastern periphery, models indicate that blocking mid-level ridging across the southern mid-latitude eastern Pacific will expand and build further through this period. This is forecast to occur in phase with substantial amplification of large-scale ridging within the westerlies across the Aleutians through much of the northeastern Pacific by 12Z Thursday. As the short wave trough approaches the British Columbia and Pacific Northwest coast, it appears that a developing split in the westerlies inland will begin to become more pronounced. Downstream short wave ridging is expected to overspread the Canadian Rockies and Prairies within the developing northern branch. Farther east, large-scale mid-level troughing is forecast to evolve across the eastern Canadian Provinces and adjacent portions of the U.S., with at least one embedded short wave trough accompanied by a modest surface cyclone across the Great Lakes through New England. At the same time, as a vigorous short wave trough continues to dig within the developing southern branch, across the Great Basin into the Southwest, downstream mid-level flow likely will become increasingly confluent east of the Rockies into the Ohio Valley. Beneath this regime, expansive cold surface ridging is forecast to build Wednesday night. As it does, a cold front trailing the cyclone will sharpen while advancing through much of central Texas, the lower Mississippi and Tennessee Valleys and Mid Atlantic Coast states by 12Z Thursday. Meanwhile, beneath modest/flat subtropical ridging, centered over the southern Gulf of Mexico and Caribbean, boundary-layer moistening will continue across the western and northwestern Gulf of Mexico, with a light southerly return flow allowing for modest moistening inland of the northwestern Gulf coast. ...Texas... Moistening inland of the northwestern Gulf of Mexico through this period is expected to occur beneath a warm and dry lower/mid tropospheric layer which will provide strong capping. Although some NAM forecast soundings across parts of central Texas continue to suggest that thermodynamic profiles could come close to thunderstorm development, with lift and destabilization above the southward advancing cold front late Wednesday night, probabilities for thunderstorms still appear less than 10 percent at this time. ...Colorado Plateau vicinity... Despite generally cool/cold thermodynamic profiles, models continue to suggest that the boundary layer may be warm enough to support some convection capable of producing lightning Wednesday afternoon and evening, aided considerably by strong mid-level cooling and lift associated with the digging southern branch impulse. ..Kerr.. 02/23/2021
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