Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jun 09 2025 05:55:56 ACUS01 KWNS 090555 SWODY1 SPC AC 090554 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1254 AM CDT Mon Jun 09 2025 Valid 091200Z - 101200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY ACROSS PARTS OF THE OHIO AND LOWER MISSISSIPPI VALLEYS INTO THE APPALACHIANS AND SOUTH ATLANTIC SEABOARD,...AS WELL PARTS OF NORTHEASTERN NEW MEXICO... ....SUMMARY... Scattered strong to severe thunderstorm development appears probable today, particularly across parts of the Ohio Valley into Appalachians, and east of the lower Mississippi Valley into eastern Gulf Coast states. ....Discussion... It appears that mid/upper ridging inland of the Pacific coast through the western Canadian Prairies and northern U.S. Rockies is beginning to become suppressed by a short wave perturbation. As this continues, a seasonably deep downstream trough, currently still digging through the northern Great Plains/Upper Midwest vicinity, is forecast to pivot east-northeastward across the Great Lakes and Ohio Valley, gradually taking on a negative tilt as it does. An initially broad, modest associated surface cyclone may deepen some, mainly across northern Ontario into the James Bay vicinity, with at least a couple of reinforcing surges of cooler air overspreading the Great Lakes region, Ohio and Mississippi Valleys. Within a belt of more modest cyclonic mid/upper flow in latitudes to the east of the southern Rockies, at least one notable meso-beta to meso-alpha scale cyclonic circulation appears to be in the process of developing near the Ark-La-Tex vicinity. It appears that this circulation will tend to migrate east-northeastward across and to the east of the lower Mississippi Valley during the day. However, the extent to which it is maintained or becomes sheared, as larger-scale troughing within the two branches of westerlies tends to come in phase, remains unclear based on latest model output. Upstream, weak mid-level troughing is forecast to dig inland of the southern California coast, through the Southwest, around the northeastern periphery of a prominent mid-level high over the subtropical eastern Pacific. Seasonably moist air appears likely to remain largely confined to a remnant frontal zone across the southern tier of the U.S., associated with the modest southern mid- and subtropical westerlies. However, a narrow plume of southerly return flow is ongoing ahead of the lead reinforcing cold front now advancing southeast of the upper Great Lakes and Midwest. ....Lower Mississippi Valley into south Atlantic Seaboard... Potential convective evolution remains unclear, but guidance remains suggestive that ongoing convective development propagating across northeastern and north central Texas will be in the process of weakening while spreading into Louisiana and upper Texas coastal areas early in the period. Additional convection is also likely to be ongoing downstream of the emerging mesoscale vortex, aided by low-level warm advection, as it migrates east of the Mississippi Valley. The impact of this convection on boundary-layer destabilization remains unclear. However, while mid-level lapse rates may be weak, with at least some insolation, boundary-layer dew points in excess of 70 F across the Gulf Coast region may contribute to sufficient destabilization to support at least scattered intensifying thunderstorm development, both upstream and downstream of the convective vortex. Some of this activity may pose a risk for, mainly, strong surface gusts. A brief tornado also might be possible, particularly near the convective vortex as long as it remains relatively well-defined. This severe risk may continue into the south Atlantic Seaboard tonight, but this remains more unclear. ....Ohio Valley into Appalachians... Moderate boundary-layer destabilization ahead of the lead cold front might provide support for scattered strong to severe thunderstorm development, including supercells, in the presence of strong deep-layer shear beneath 40-60+ kt southwesterly mid/upper flow. Toward mid to late afternoon, it is possible that modestly deepening surface troughing across the upper Ohio Valley into the lee of the Allegheny front may provide a better defined focus for this threat. ....Great Lakes vicinity... Convection-allowing model output and associated guidance suggest that destabilization and shear may become supportive of convection capable of producing severe hail and wind in a narrow corridor ahead of a secondary surface cold front (closer to the mid-level cold core overspreading the Great Lakes), as it advances across and east-southeast of Lake Michigan this afternoon. ....Southern Rockies through northwestern Gulf coast... Extensive convective outflow appears likely to be progressing into and through the upper Texas coastal plain by the beginning of the period, and perhaps gradually stalling across parts of south central Texas into the Pecos Valley. The gust front might still be a focus for widely scattered strong thunderstorm development early in the day, otherwise the extent of the outflow's stabilizing influence remains unclear, particularly later in period to the lee of the southern Rockies. Downstream of the Southwestern mid-level tough, models suggest that destabilizing, moist upslope flow into the Raton Mesa/eastern slopes of the Sangre de Cristo Mountains might become supportive of a couple of supercells and one or two small upscale growing thunderstorm clusters. Beneath modest to weak northwest mid-level flow, this activity may pose a risk for severe hail and wind while propagating off the higher terrain through this evening. Continuing development into portions of west Texas overnight is more unclear. ...Kerr/Squitieri.. 06/09/2025 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .