Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Wed Apr 26 2023 16:00:00 ACUS01 KWNS 261943 SWODY1 SPC AC 261941 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0241 PM CDT Wed Apr 26 2023 Valid 262000Z - 271200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF CENTRAL TEXAS AND THE CENTRAL FLORIDA PENINSULA... ....SUMMARY... A few tornadoes (possibly some strong), very large/destructive hail, and severe thunderstorm gusts are expected over parts of central Texas this afternoon and evening. Very large hail and damaging winds remain a threat over parts of Florida into far southeast Georgia this afternoon and early evening. ....20Z Update... Adjustments were made to the Category 3/Enhanced risk area (and associated probabilities) in central TX to align with the warm sector along and just south of an outflow boundary which is behaving like an effective warm front. Storms that form just ahead of the dryline and can traverse the outflow boundary area will likely become supercells capable of very large hail, hurricane-force wind gusts, and a couple of tornadoes. Any storms that can traverse the boundary for a long enough period of time may ingest locally higher amounts of streamwise vorticity, which may support the development of a strong tornado. Please see MCD #0623 for more information. The Category 2/Slight risk across northern FL was extended northward to include portions of far southeast GA, where supercell structures have produced reported golfball size hail, and where MRMS MESH suggests that significant severe hail may be occurring. Given the presence of steep lapse rates and adequate deep-layer shear, the severe hail threat may continue into the early evening hours. Finally, the Category 2/Slight risk in Texas was expanded farther east into central LA. Here, a cluster of storms may persist into the overnight hours and support short bowing structures capable of damaging gusts. ...Squitieri.. 04/26/2023 ..PREV DISCUSSION... /ISSUED 1125 AM CDT Wed Apr 26 2023/ ....Texas into the Lower Mississippi Valley... Elevated convection is ongoing late this morning across north-central TX and far southern OK. This activity is related to low-level warm advection and ascent preceding an upper trough over the southern High Plains. Recent surface observations show a warm front draped across north-central into east TX. Most 12Z guidance continues to suggest that this warm front will attempt to lift northward this afternoon as the upper trough/low ejects slowly eastward across the southern Plains. A surface dryline is also forecast to mix eastward across parts of west into central TX, and provide a focus for robust convective development this afternoon. Convective evolution across north/central TX this afternoon will be somewhat complicated by the ongoing convection near the Red River. These thunderstorms will probably tend to limit the northward advance of the warm front. Still, moderate to locally strong instability appears likely to develop by peak heating this afternoon south of the warm front and east of the dryline as steep mid-level lapse rates/an EML overspread the warm sector, and as surface dewpoints generally increase into the mid to upper 60s. Current expectations are for multiple surface-based supercells to initiate along/near composite the outflow/warm front/dryline intersection early this afternoon, probably no later than 19-20Z. Given the presence of steep mid-level lapse rates and 40-50 kt of deep-layer shear, this initially semi-discrete convection will pose a threat for very large hail (2-3+ inch diameter) as it spreads east-southeastward this afternoon across north TX. The threat for a few tornadoes will also exist, as low-level flow will strongly veer from east-southeasterly at low levels to westerly at mid levels, enhancing the low-level hodograph and effective SRH. Strong tornado potential should remain focused with any supercell that can remain anchored along the warm front. The initially semi-discrete supercells will likely grow upscale into a bowing complex/MCS by early evening. As this mode transition occurs, the threat for severe/damaging winds will increase, with some potential for significant (75+ mph) gusts across north-central into east TX. 12Z guidance shows this MCS continuing into LA and parts of central/southeast TX this evening/overnight. While some decrease in updraft intensity may eventually occur, there will probably be a continued threat for scattered damaging winds given a reservoir of favorable buoyancy. Some chance for a couple of supercells may also exist over central TX this afternoon, driven by modest low-level warm advection. If robust thunderstorms can form, they would pose a threat for all severe hazards, including very large hail. Have therefore expanded the Slight Risk southward to include more of central/southeast TX to account for this severe potential. An isolated severe threat should also persist tonight into portions of the lower MS Valley, as generally linear convection spreads eastward from TX. ....Florida... Based on recent visible satellite imagery, mostly clear/sunny conditions are present over the FL Peninsula. The eastern extent of a remnant EML, shown in the fairly steep 700-500 mb lapse rates on the 12Z TBW/15Z XMR soundings, has overspread much of the FL Peninsula. Robust diurnal heating of a rich low-level airmass will contribute to a moderately to strongly unstable airmass, with MLCAPE generally around 2000-2500+ J/kg. Even with low-level winds expected to remain fairly weak, enhanced mid/upper-level flow will foster 40-50 kt of effective bulk shear and updraft organization. Compared to the past two days, it appears likely that multiple supercells capable of producing both very large hail and strong/damaging winds will develop this afternoon over the northern/central FL Peninsula along both sea breezes and residual outflow boundaries, and subsequently spread southward through the early evening. $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .