re: Multi-day Severe Weather Threat: 3/23-3/24

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Across southeast Arkansas, northern Louisiana, and northwest Mississippi, a more volatile environment will develop Friday evening/early overnight. More discrete convection is anticipated on the southern periphery of the aforementioned QLCS. The more discrete mode, combined with greater instability and strong shear should allow for multiple supercells to develop across northern Louisiana and southern Arkansas and move northeastward. Low-level hodographs are very favorable in this region with 0-500m SRH around 200 m2/s2 and 0-1km SRH 300+ m2/s2. Therefore, any sustained supercells will be capable of producing strong to intense (EF3+) tornadoes, with long-track tornadoes possible with any longer-lived, undisturbed supercells. 00Z HREF members showed a variety of solutions which cast some uncertainty on the forecast. WRF members are notably less bullish with warm sector supercell development from northeast Louisiana into northern Mississippi while the HRRR was most aggressive with convective coverage and environment. After further investigation it appears the more aggressive HRRR solution can be attributed to a more robust mass response during the afternoon/early evening hours. This results in a pronounced shortwave trough which can be seen at 700 and 850mb and reflected as a significant confluence zone at the surface. Not only does this act as a forcing for storm development, but it also acts as moisture convergence with a more broad region of 70+F dewpoints. In this scenario, numerous strong tornadoes would be likely, with the potential for several intense tornadoes. Despite being the most aggressive, this solution does not seem unreasonable as similar low-level confluence features can been on both the 00Z GFS and the 18Z ECMWF. As is often the case, the severity of the tornado threat across the moderate risk will be modulated by mesoscale influences in the region. As the event approaches, these mesoscale effects may become more clear and allow the greatest risk corridor to become better defined. ..Bentley/Weinman.. 03/24/2023

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