Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Mar 16 2023 19:26:11 ACUS01 KWNS 161926 SWODY1 SPC AC 161924 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0224 PM CDT Thu Mar 16 2023 Valid 162000Z - 171200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER MUCH OF NORTHEAST TEXAS...SOUTHERN OKLAHOMA...AND INTO THE ARKLATEX AREA... ....SUMMARY... Scattered severe thunderstorms are expected mainly across southern Oklahoma and into north-central and northeastern Texas, accompanied by a risk of large hail and isolated tornadoes. ....Southern OK into TX... Storms continue to increase in coverage and intensity along the cold front, now extending from near Tulsa OK to just northwest of Wichita Falls TX with indications of large hail. These storms are tied to the cold front which is tending to undercut the cells with cool air. As a result, storms along this boundary may only have brief tornado potential as it continues across the Red River, and encounters larger SRH values. Elsewhere, storms persist in the warm advection zone over northeast TX and across the Arklatex, but temperatures are currently cool which is limiting instability and tornado potential. With time, more unstable air may make it into the area, and a few storms could become supercells. Other warm-sector storms have formed northwest of Houston where dewpoints are in the upper 60s F, and these may eventually have severe potential as they move into a better low-level shear environment. For more information see mesoscale discussion 292. A few cells may also produce large hail late this evening and overnight near the tail end of the front near and east of the Rio Grande Valley. Here, capping will be a concern and will likely limit southward extent. ...Jewell.. 03/16/2023 ..PREV DISCUSSION... /ISSUED 1100 AM CDT Thu Mar 16 2023/ ....Synopsis... The northern branch of the prevailing split flow across the northern mid-latitude Pacific into western North America has become rather amplified. On the lead edge of this regime, models continue to indicate that mid-level troughing will gradually consolidate across the northern Great Plains and upper Mississippi Valley/Great Lakes vicinity. It appears that this will include at least a couple of smaller scale perturbations contributing to the evolution of a broad embedded low, and increased phasing with the lower amplitude southern branch across and east-northeast of the Mississippi Valley. A notable southern branch perturbation, emerging from the Southwest, likely will become increasingly sheared as it accelerates through increasingly confluent mid-level flow across the southern Great Plains Red River Valley into the lower Ohio Valley today through tonight. However, this will be accompanied by intensifying southwesterly flow along this corridor, including 50-70+ kt around 500 mb. In lower-levels, a broad belt of 30-50 kt south-southwesterly flow is currently nosing across the southeastern Great Plains toward the Ohio Valley. However, this is still largely focused along the tight height/pressure gradient on the western periphery of a prominent surface ridge, the center of which is forecast to gradually shift east of the southern Atlantic Seaboard through tonight. Beneath this regime, dry/potentially cold boundary-air has been maintained across the Sabine River/Texas Piney Woods through the lower half of the Mississippi Valley, and models suggest that this will be slow to modify. At the same time, another significant cold intrusion is well underway to the lee of the Rockies, with strong surface pressure rises already ongoing across much of the Texas/Oklahoma Panhandle region. The frontal zone on the leading edge of the cold air is forecast to rapidly advance southward across much of the Red River Valley and northwest Texas by late this afternoon, into the lower Mississippi Valley and northwestern Gulf of Mexico by 12Z Friday. While significant cyclogenesis is forecast along the troughing between the surface ridges, across the Upper Midwest and Great Lakes region, it appears that the rapidly advancing trailing cold front will undercut and cut off the ongoing moist return flow across the southern Great Plains. Models continue to generally indicate that this will preclude substantive destabilization across and northeast of the Ozark Plateau vicinity. ....Southern Great Plains... There may be some window of opportunity for appreciable boundary-layer destabilization along/just ahead of the cold front from southwestern Oklahoma into southeastern Kansas through early this afternoon. If mid-level cooling becomes sufficient to weaken inhibition prior to the arrival of the front, thunderstorms capable of producing mainly severe hail and wind are possible. However, this risk may be relatively short-lived, with even the potential for severe hail diminishing fairly quickly as convection is undercut by the cold front. At least a somewhat longer-lived risk for severe weather still appears like it could initiate in response to a corridor of stronger low-level warm advection near/east-northeast of the intersection of the cold front and a sharpening dryline. It seems most probable that this will occur east of the Fort Sill/Wichita Falls vicinities around 20-21Z, in an environment characterized by sizable mixed-layer CAPE of 1000-2000+ J/kg, steep-lapse rates and strong deep-layer shear. This may initially include a few discrete supercells with potential to produce large hail and perhaps a couple of tornadoes, before growing upscale into an eastward propagating cluster or line. How far east the severe weather potential spreads remains unclear, and will be limited by the tendency to become undercut by the advancing cold front and/or ingesting less unstable air with eastward extent into the lower Mississippi Valley. Otherwise, higher resolution model output, in particular, suggests that a separate area of strong/severe thunderstorm potential may develop late this evening near/south through east-southeast of the Del Rio area. It appears that this may be supported by forcing for ascent associated with a southern branch perturbation, near/along the cold front as it reaches the Rio Grande River vicinity. $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. 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