SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1153 PM CST Thu Nov 12 2020 Valid 141200Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN OKLAHOMA/OZARKS/ARKLATEX... ...SUMMARY... Isolated severe thunderstorms may occur across eastern Oklahoma and the Ozarks/Ark-La-Tex regions late Saturday afternoon and night. ...Synopsis... Large-scale trough amplification will occur from the northern/central Rockies toward the Upper Midwest/upper Great Lakes Saturday and Saturday night, with a very strong (100+ kt) polar jet developing eastward over the middle Mississippi Valley/Ohio Valley Saturday night. Related surface cyclogenesis is expected to occur over the Upper Midwest Saturday night, with a surface cyclone deepening from Iowa toward the Lake Superior/Lake Michigan vicinity through early Sunday morning. Modest-caliber low-level moisture will steadily advect north-northeastward in advance of an east/southeastward-moving cold front that will reach the middle Mississippi Valley/ArkLaTex late Saturday night. ...Eastern Oklahoma/Ozarks/ArkLaTex... Scattered showers and thunderstorms are likely to be ongoing Saturday morning across much of the region, with little if any severe-weather potential expected early in the day. This precipitation will tend to hinder the northward extent of modest destabilization later in the day, although at least some severe risk is expected to materialize late Saturday afternoon and evening related to the south/southwest fringes of this early-day precipitation/residual cloud cover. It is probable that low/some middle 60s F surface dewpoints will develop north/northeastward into the region by late Saturday afternoon and Saturday night in advance of the east/southeastward-moving cold front. In terms of guidance, 00Z NAM/GFS runs have trended a bit stronger with surface cyclogenesis/moisture return as similar to prior ECMWF solutions (which have been synoptically stronger and modestly more unstable), further lending credence to at least some late-day/evening severe-weather risk across the region. Even while mid-level lapse rates will not be particularly steep at these latitudes, MLCAPE could reach around 500-750 J/kg particularly across eastern Oklahoma/western Arkansas by early evening. Very long hodographs (45-60 kt effective shear) would support the potential for some fast-moving semi-discrete supercells and linear segments, with at least some potential for damaging winds and possibly a tornado risk. Uncertainties regarding the exact degree of late-day destabilization preclude a categorical Slight Risk at this time. ..Guyer.. 11/13/2020
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