Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 09 2023 05:02:06 ACUS02 KWNS 090501 SWODY2 SPC AC 090500 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1200 AM CDT Fri Jun 09 2023 Valid 101200Z - 111200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SATURDAY INTO SATURDAY NIGHT ACROSS PARTS OF NORTH CENTRAL AND NORTHEASTERN TEXAS AND ADJACENT PORTIONS OF SOUTHERN OKLAHOMA...SOUTHWESTERN ARKANSAS AND NORTHWESTERN LOUISIANA... ....SUMMARY... One or two organized clusters of thunderstorms may develop across parts of the southern Great Plains Red River Valley into north central and northeastern Texas Saturday through Saturday night, accompanied primarily by a risk for large hail and strong wind gusts. ....Synopsis... The westerlies across much of North America are likely to remain weak into and through this period. Another fairly prominent mid-level high developing within the prevailing split flow is forecast to slowly shift eastward across the Canadian Prairies, with mid-level troughing consolidating and digging to its southeast, into the Upper Midwest by late Saturday night. Downstream, a seasonably deep, elongated mid-level low (currently centered over New England) is forecast to finally reform east of the Canadian Maritimes, as significant surface cyclogenesis proceeds offshore, across the northwestern Atlantic. However, seasonably dry, mild and generally stable air likely will be maintained across a broad area east/northeast of the Mississippi Valley and portions of the northern Great Plains. In the southern mid- and subtropic latitudes, models indicate that broad, weak mid-level troughing will be maintained across much of the Gulf Basin into southwestern Atlantic, downstream of similarly amplified mid-level ridging to the east of the southern Rockies, as another developing mid-level low turns eastward into the southern California coast. It does appear that a less prominent short wave perturbation (currently approaching Baja) will progress inland, and gradually around the northern periphery of the ridging into the downstream troughing by Saturday night. There is considerable spread within the model output concerning this perturbation emerging from the subtropical eastern Pacific. However, a gradually moistening air mass across the northwestern Gulf Coast into the Great Plains is forecast to become characterized by increasingly large instability, and perhaps increasing potential for severe storm development. ....Southern Great Plains into lower Mississippi Valley... Given the generally weak flow regime, relatively subtle forcing for ascent, and increasing potential instability, the predictability concerning possible convective developments has been (and might still be) relatively low. However, there has been a persistent signal that one or two significant clusters of storms could develop, in the presence of thermodynamic profiles becoming characterized by steepening lower/mid-tropospheric lapse rates and mixed-layer CAPE on the order of 2000-3000+ J/kg. Based on the latest NAM, Rapid Refresh and convection allowing model output, it still appears that a cluster of warm advection driven thunderstorm activity may be ongoing early Saturday across parts of central/eastern Oklahoma. Aided by increasing inflow from the seasonably moist boundary-layer, convection may undergo at least a period of intensification into the afternoon, with possible increasing organization and risk for strong wind gusts across the Red River Valley into north Texas, in association with a developing MCV. Whether this activity will be maintained eastward and/or southeastward into the lower Mississippi Valley/northwestern Gulf Coast later Saturday afternoon and evening is more unclear. Latest model output appears more suggestive that this initial cluster may tend to weaken by late Saturday afternoon, with stronger new thunderstorm development becoming focused near the intersection of its trailing outflow boundary and the dryline, across parts of north central Texas. Near the leading edge of warmer and more strongly capping elevated mixed-layer air, and in the presence of strong deep-layer shear (due to pronounced veering of the wind fields with height and perhaps convective augmentation of the westerly/northwesterly mid/upper flow), the environment may become conducive to supercells capable of producing large hail and perhaps a tornado, initially. Aided by forcing for ascent associated with low-level warm advection, this activity probably will grow upscale while propagating southeastward along the outflow boundary. This may be accompanied by another swath of potentially damaging wind gusts, before convection weakens in the presence of waning boundary-layer instability/increasing mid-level inhibition late Saturday evening. ...Kerr.. 06/09/2023 $$ = = = 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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