SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1133 PM CST Mon Nov 23 2020 Valid 241200Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS... ...SUMMARY... Severe thunderstorms are possible late afternoon Tuesday into Tuesday night across portions of the southern/central Plains, Ozarks, Mid-South, and lower Mississippi Valley. Large hail and severe gusts are the primary hazards. ...Central/Southern Plains to Lower MS Valley... Strong mid-level vort with an accompanying 90kt+ speed max are digging into the lower CO River Valley at 0530z. This feature will shift east into southern NM by 18z then into the southern High Plains by late afternoon. 120m 12hr height falls, along with a focused exit region of the aforementioned jet, suggest convection will develop by early afternoon along the front over the western OK/TX Panhandle region. Forecast soundings suggest the strongest boundary-layer heating will be noted across this region, and despite the relatively dry boundary layer, profiles exhibit more than adequate instability for surface-based convection along the front. RAP forecast sounding for DHT exhibits ~900 J/kg SBCAPE with steep lapse rates and -22C at 500mb. Hail production should be efficient with this activity, although it may be initially sub-severe. Late-evening surface data suggests mid 50s surface dew points are advancing north across the Edwards Plateau and this moisture plume should return across western OK prior to the main convective development. While large-scale forcing for ascent should ultimately lead to more organized line segments downstream, initial activity across the far northeastern TX Panhandle into northwestern OK should be supercellular in nature. This early activity could certainly produce very large hail before the convective mode is disrupted. Prior to this disruption, a few brief tornadoes are also possible. As large-scale forcing spreads across western OK, a more organized band of storms should evolve then propagate east with an attendant hail/wind threat. Given that the LLJ will be focused into northeast OK/Ozark Plateau region, the primary corridor for organized convection should spread north of I-40 across OK into this region. Farther south, it's not entirely clear how active the warm sector will be prior to the cold frontal passage across northeast TX into western AR. HRRR is the most aggressive high res model in generating discrete storms in the warm sector by 25/00z, then along the front as it advances into this more moist air mass. However, stronger forcing will remain north of this region and there is reason to believe convection may be a bit more isolated across this region. Will maintain MRGL Risk across this area due to uncertainty in storm coverage/intensity. ..Darrow/Squitieri.. 11/24/2020
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