SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Sat Oct 24 2020 Valid 251200Z - 261200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms appears negligible across the U.S. Sunday through Sunday night. ...Synopsis... Mid/upper ridging appears likely to remain highly amplified across the eastern Pacific through this forecast period. Models indicate that there may be some northeastward redevelopment of a prominent embedded high across the mid-latitudes, and the larger-scale ridging might take on more of a positive tilt, as a short wave trough is forced northeastward around its northwestern periphery, ahead of a mid-level low near the Aleutians. As this occurs, a vigorous downstream short wave impulse is forecast to sharply dig to the lee of the ridging, accompanied by larger-scale upper trough amplification along a positively tilted axis across the Intermountain West and Rockies. This may include the gradual evolution of an embedded mid-level low across the southern Great Basin by the end of the period. At the same time, models indicate that a short wave trough emerging from the Arctic latitudes will continue digging across and southeast of Saskatchewan/Manitoba. Downstream, of the Great Basin low, this will contribute to an increasing confluent mid-level regime to the lee of the northern Rockies, beneath which cold surface ridging is forecast to build and dam southward through much of the high plains by daybreak Monday. This will reinforce a cold front which has already advanced through much of the Great Plains, Mississippi and Ohio Valleys, and is in the process of advancing across the northern Atlantic Seaboard. A relatively moist air mass prevails along and south of the lead frontal zone across the northwestern Gulf of Mexico and Gulf coast vicinity, and more so across parts of the Southeast, ahead of weak mid-level troughing now progressing eastward across the eastern Gulf States. Tropically moist conditions are now confined to parts of the southeastern Gulf of Mexico and the Caribbean, northward into the Florida Straits vicinity, ...Southeast... The weak mid-level troughing may be in the process of accelerating northeastward, but generally to the lee of the southern Appalachians, and progressing across/along south Atlantic coastal areas by 12Z Sunday. Although north-northeastward advection of the tropical moisture will take place well offshore, low/mid-level moisture near the Carolina coast may contribute to thermodynamic profiles supportive of weak thunderstorm activity (despite weak lapse rates), aided by the large-scale forcing for ascent. ...Southern Great Plains... The leading edge of the low-level cold intrusion likely will progress well south of the colder air aloft associated with the evolving mid/upper troughing, However, moistening on southerly low-level flow, above the cold front, may support weak CAPE and scattered thunderstorm activity aided by warm advection, focused mainly near the mid-level baroclinic zone (where inhibition will become weaker) by late Sunday night. ...Southern Great Basin/Plateau... Mid-level cooling and forcing for ascent ahead of the digging short wave trough may contribute to weak destabilization supportive of scattered thunderstorm activity Sunday afternoon through Sunday night. ..Kerr.. 10/24/2020
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