Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Mar 09 2023 19:46:47 ACUS01 KWNS 091946 SWODY1 SPC AC 091945 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0145 PM CST Thu Mar 09 2023 Valid 092000Z - 101200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT PARTS OF CENTRAL TO EAST TEXAS INTO WEST CENTRAL/SOUTHWEST ALABAMA... ....SUMMARY... Isolated strong to severe thunderstorm development remains possible late this afternoon into tonight from portions of central/east Texas to western Alabama. ....20Z Update... ....East of the Rockies... Only minor changes have been made, to the categorical (10 percent probability) thunderstorm line, generally to account for the continuing progression of the synoptic features. For further details, please refer to the 1630Z discussion, appended below. ....Pacific Coast states... A significant mid-level trough, and embedded low, will gradually turn eastward toward northern Pacific coastal areas later today through tonight. An associated deepening, and occluding surface cyclone is forecast to remains offshore of the Washington coast, but a trailing cold front will advance inland across western into central Oregon and northern California. It appears that the mid-level cold core of the system, including 500 mb temperatures of -30 to -35 C, may contribute to post-frontal boundary-layer destabilization near Oregon coastal areas by 09-12Z. Coupled with an increasing onshore low-level flow component, this is expected to support scattered deepening convection, some of which may become capable of producing lightning. Farther south, a plume of lower/mid tropospheric moisture return, emanating from the southern mid- and subtropical eastern Pacific, will spread inland ahead of the cold front, across the California coast and Sierra Nevada. Despite relatively warm mid-levels, forecast soundings indicate conditionally unstable profiles developing late this evening into the overnight hours, rooted mainly well above the surface, in the lower/mid troposphere. As winds at these elevations take on a strengthening westerly component, orographic forcing for ascent may contribute to convection occasional capable of producing lightning along the western slopes of the Sierra after 06Z. In lower elevations to the west, probabilities for weak thunderstorm potential are more uncertain. However, they might not be negligible across the Sacramento into San Francisco Bay areas overnight, where/when lift ahead of the inland advancing cold front may be enhanced by forcing for ascent near the southern periphery of the mid-level trough. ...Kerr.. 03/09/2023 ..PREV DISCUSSION... /ISSUED 1030 AM CST Thu Mar 09 2023/ ....Central/east TX to western AL... Primary shortwave trough ejecting from the central Great Plains to the southern Great Lakes will yield a largely zonal regime across the southern states with minor mid-level perturbations embedded within the flow. A persistent baroclinic zone from TX to AL will strengthen by late afternoon as differential heating is underway with surface temperatures expected to rise into the 80s F across a large swath of the warm sector. Weak to moderate MLCAPE of 500-1500 J/kg is anticipated along and south of the Edwards Plateau in TX to the AR/LA border and west-central/southwest AL. Isolated to scattered showers and thunderstorms are most likely this afternoon from southeast OK and the Ark-La-Tex to central AL, on the cool side of the surface front. With generally weak MUCAPE, and a cool/stable boundary layer in place near and northeast of the front, storms should remain elevated with small hail as the primary threat. One exception may be along a confined portion of the front in the west-central/southwest AL vicinity, where weak low-level warm theta-e advection across this portion of the front might support a supercell or two. The spatiotemporal window for this conditional potential to be realized appears limited given the weak large-scale ascent. A swath of scattered thunderstorm development is expected this evening from the AR/LA border southwest into the Edwards Plateau of TX along and behind the surface cold front, yielding south/southeast acceleration of the front tonight. While isolated damaging winds are possible immediately along the front, the main threat should be isolated severe hail given the undercutting nature of the boundary. The greatest potential for supercells with mid-level rotation should be across the southwest portion of the outlook area in south-central TX. Here, steeper mid-level lapse rates and ample speed shear within the cloud-bearing layer could result in large hail tonight. $$ = = = 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) .