Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Mar 11 2023 20:02:02 ACUS01 KWNS 112001 SWODY1 SPC AC 112000 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0200 PM CST Sat Mar 11 2023 Valid 112000Z - 121200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF EASTERN OKLAHOMA INTO NORTHERN MISSISSIPPI... ....SUMMARY... Scattered severe thunderstorms, capable of large to very large hail, will remain possible this evening and overnight across eastern Oklahoma into Arkansas. ....20Z Update... The primary change to this outlook was to expand the Slight Risk farther east into northern MS for tonight. Some of the latest high-resolution guidance have been trending upwards in intensity of a bowing segment of convection originating from earlier supercells across AR. After 06Z, this line of storms may progress across northern MS with a threat of damaging gusts. The severe hail threat remains on track across eastern OK into western AR for this evening. Multiple hail producing supercells are likely, and a few instances of up to baseball sized hail is possible. The primary limiting factor to a more widespread severe hail threat is the potential for a rapid upscale growth of storms, which may occur after storms achieve supercell status, hence limiting the coverage of significant-severe hail. Another change to the outlook was to add a Category 1/Marginal Risk for portions of the central valley region of CA. Current observations depict upper 50s to low 60s F surface dewpoints amid warming surface temperatures. Continued diurnal heating will foster a well-mixed but moist boundary layer and associated steep low-level lapse rates. Forecast soundings depict elongated, mostly straight hodographs, suggesting transient, low-topped supercells would be the primary mode of convection. Some guidance also hints at relatively high amounts of low-level vertically oriented vorticity co-located with the better surface-based buoyancy. As such, low-level stretching with the more persistent supercells may support a brief tornado threat. The best chance for severe will be in the 21-01Z time frame. ...Squitieri.. 03/11/2023 ..PREV DISCUSSION... /ISSUED 1030 AM CST Sat Mar 11 2023/ ....OK-TX into the lower MS Valley... Located to the south of a more pronounced mid-level low over the northern Great Plains, a low-amplitude disturbance embedded within strong westerly flow, will move from the central High Plains to the Ozarks/OH Valley during the period. Visible satellite imagery this morning shows an extensive stratus shield/moist sector over eastern OK/TX into AR/LA. As a warm front advances north during the day into eastern OK/AR, a low will develop east across the Red River Valley while a cold front progresses southeast across OK and a dryline sharpens over north TX. Steep 700-500 mb lapse rates were observed on 12z raobs over the southern Great Plains (7.9 deg C/km at Norman, OK). Gradual cooling temperatures in the mid-levels will overspread a destabilizing warm sector this afternoon. Forecast soundings show an initial capping inversion gradually weakening by late afternoon with temperatures warming into the 80s along the dryline portion of the overall risk area. Ample deep-layer shear will favor supercells with the initial storms. Model guidance continues to show scattered thunderstorms initially developing over eastern OK this evening and spreading east into AR during the evening and into the overnight. Some upscale growth into a mix of supercells and linear structures is indicated by the models. The predominant risk will be large to very large hail with the mostly elevated activity. A gradual weakening is expected as storms eventually move into northern MS late tonight as buoyancy lessens with east extent. Farther south along the dryline, convective initiation is still uncertain across north TX. Models continue to show a limited probability for storm initiation across this corridor. Nonetheless, if a storm or two were to develop and become sustained, a severe risk could materialize for a few hours. ....Southwest States and CA... A belt of strong/low-amplitude westerlies coupled with steep lapse rates and modest moisture could yield a couple of stronger storms late this afternoon/early evening across the California San Joaquin Valley and/or across southern Nevada into southern Utah/far northern Arizona. However, organized severe storms are not currently expected. $$ = = = 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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .