Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Mar 30 2024 12:51:32 ACUS01 KWNS 301251 SWODY1 SPC AC 301249 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 AM CDT Sat Mar 30 2024 Valid 301300Z - 311200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF EASTERN INDIANA TO PARTS OF WEST VIRGINIA AND SOUTHWESTERN PENNSYLVANIA... ....SUMMARY... Isolated severe hail and/or damaging gusts may occur across parts of the Ohio Valley into West Virginia this afternoon/evening. ....Synopsis... The mid/upper-level pattern over the western CONUS will remain dominated by troughing related to a synoptic-scale cyclone -- centered initially off the CA coast about 150 nm west of SFO. The cyclone will dig southeastward through the period, with its center remaining just offshore, but elongating northeastward as several vorticity lobes pivot into the northeastern quadrant of the gyre. Meanwhile, a northern-stream trough now over southern Yukon and northern BC will dig southward to the inland Pacific Northwest. This will cause a phasing of northern and southern streams into a more full-latitude, positively tilted trough by the end of this period and early day 2, from the northern Rockies across southern CA, to Pacific waters well west of northern Baja. Associated cold air aloft and marginal (but adequate) low/middle-level moisture will support isolated thunderstorm potential over much of CA and northern/western NV. Downstream, southwest flow aloft will spread across most of the Intermountain West and Rockies, with several embedded/low-amplitude perturbations -- one of which may contribute enough instability aloft to support isolated thunder over the central High Plains. East of the Rockies, largely zonal mid/upper flow is forecast, with the most convectively consequential perturbation now evident in moisture-channel imagery over portions of Lower MI, Lake Michigan, IL, and IN. This feature is somewhat elongated in the flow, with western and eastern components -- a general geometry that should be maintained as it shifts eastward to the northern Mid-Atlantic region through this evening. Surface analysis at 11Z revealed a frontal-wave low over northwestern IL, with cold front southwestward over western OK and the TX Panhandle. A warm front was drawn east-southeastward from the low near an IND-CVG-HTS line, to a weak low between LYH-CHO. Though initially slowed somewhat by outflow from morning/midday precip over the Ohio Valley region, the warm front should advance northeastward into parts of OH and western PA today, as the main low moves eastward to eastern OH by 00Z. At that time, the cold front should extend from the low over southern parts of IN/IL/MO, to what by then should be a stationary to warm front across northern OK into southeastern CO. ....Ohio Valley and WV... An ongoing area of precip and isolated, embedded, non-severe thunderstorms is apparent in radar animations from WI southeastward to OH, in the combined zones of large-scale ascent related to warm advection and DCVA (preceding the mid/upper perturbation). This activity and its cloud shield are expected to proceed eastward through the central/northern Appalachians and Mid-Atlantic today. Favorable boundary-layer destabilization is most probable behind that activity, as the western lobe of the mid/upper perturbation approaches and passes over the area. Clearing, insolation, theta-e advection, and mass convergence near the cold front/low should overcome remaining MLCINH by mid/late afternoon, supporting widely scattered thunderstorms. Activity should move eastward to southeastward, offering isolated severe hail and damaging gusts. Though low-level moisture still will be on the weak side, and tempered somewhat by boundary-layer mixing, surface dewpoints should reach the mid 40s to low 50s F by that time, combining with steep low/middle-level lapse rates to enable 500-1500 J/kg MLCAPE. The well-mixed boundary layer will support strong to marginally severe downdrafts with the most intense cells. Also, and despite somewhat veered/southwesterly surface winds, low-level and deep shear still will support some supercell potential with large hail. Forecast soundings reasonably depict 45-55-kt effective-shear magnitudes over the region. Activity should weaken east of the higher terrain this evening, as it moves over a progressively deeper, more-stable boundary layer. ...Edwards/Leitman.. 03/30/2024 $$ = = = 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) .