Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Mar 08 2023 17:30:38 ACUS02 KWNS 081730 SWODY2 SPC AC 081728 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1128 AM CST Wed Mar 08 2023 Valid 091200Z - 101200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY AFTERNOON INTO EVENING ACROSS PARTS OF SOUTHERN ARKANSAS AND NORTHERN MISSISSIPPI INTO ADJACENT PORTIONS OF ALABAMA...AND PERHAPS THURSDAY EVENING ACROSS PARTS OF TEXAS... ....SUMMARY... Strong thunderstorms may impact a corridor from southern Arkansas into northern Alabama Thursday afternoon and evening, and perhaps portions of central Texas Thursday night. A couple of these may be accompanied by at least some severe weather potential, mainly in the form of hail. ....Synopsis... Within the large-scale flow across the eastern Pacific into the western Atlantic, models indicate that blocking will remain prominent in the higher latitudes. This likely will include one lingering mid-level high near the Aleutians and another over the northeastern Canadian Arctic. In between, general larger-scale mid-level troughing will persist, with a number of notable progressive short wave perturbations. This is forecast to include one trough and embedded low pivoting into the northern U.S. Pacific coast. While downstream short wave ridging builds across the eastern Great Basin into the central Great Plains by late Thursday night, a trough to the east appears likely to advance east-northeast of the lower Missouri Valley into the upper Great Lakes/lower Ohio Valley vicinity. In lower latitudes, models indicate that broad mid-level ridging will persist across much of the southern tier of the U.S., although the lead short wave trough may contribute to some suppression of mid-level heights near/north of the Red River and Ark-La-Tex into the eastern Gulf Coast states. Cold/potentially cold surface ridging, still entrenched across most areas to the east of the Rockies early Thursday, will tend to suppress substantive surface cyclogenesis as the lead mid-level trough migrates east of the Rockies. However, an area of low pressure may begin to form late Thursday evening into early Friday, along the primary low-level baroclinic zone across parts of the Mid South into lower Ohio Valley. In its wake, the shallow leading edge of the cold surface-based air (initially extending from the Edwards Plateau of Texas into the lower Mississippi Valley at 12Z Thursday) probably will shift southward toward the northwestern/north central Gulf coastal plain. ....Southern Great Plains/lower Mississippi Valley vicinity... Inhibition associated with the remnants of a plume of elevated mixed-layer air, and warm layers with weak lapse rates farther aloft, may continue to confine thunderstorm development to where weak destabilization (associated with moisture return) above/to the cool side of the surface front is maintained. It appears that the most substantive instability, perhaps including CAPE on the order of 500-1000 J/kg, will generally be focused in a narrow corridor near and to the immediate north of the front. Along this corridor, a combination of forcing for ascent associated with low-level warm advection and the gradual suppression of mid-level heights may support intensifying thunderstorm development by Thursday afternoon across parts of southeastern Arkansas into northern Mississippi. Given the stable surface-based layer, rather modest CAPE, and weak to modest low-level flow, the potential for damaging wind gusts remains uncertain. However, if convection is able to consolidate and organize in the presence of sufficiently strong cloud-bearing layer shear, a few strong surface gusts might not be out of the question before activity weakens while continuing east-southeastward through parts of northern/central Alabama Thursday evening. Otherwise, the strong deep-layer shear probably will contribute to the potential for at least marginally severe hail in the stronger and, mainly, more discrete storms. Meanwhile, across northeastern into central Texas, and southwestward toward the Edward Plateau/adjacent Rio Grande Valley vicinity, convective potential is more unclear through the period, due to stronger mid/upper inhibition and weaker (or at least more uncertain) mid/upper support. However, isolated to widely scattered strong storms posing some risk for severe hail may not be out of the question, particularly Thursday evening. ....Northern California... Forecast soundings suggest that weak conditional instability may develop by late Thursday night along the western slopes of the northern Sierra Nevada, perhaps supporting convection capable of occasionally producing lightning prior to 12Z Friday. ...Kerr.. 03/08/2023 $$ = = = 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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