Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Mar 21 2023 09:01:02 ACUS48 KWNS 210900 SWOD48 SPC AC 210859 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0359 AM CDT Tue Mar 21 2023 Valid 241200Z - 291200Z ....DISCUSSION... Broad upper troughing is expected to extend across the CONUS early D4/Friday, with one embedded shortwave trough over KS/OK and another farther west over the Southwest. Expectation is for the lead wave to gradually move northeastward, while the Southwest wave moves quickly across the southern Plains. Interaction between these two shortwaves is expected to result in the development of a mid-latitude cyclone over the OH Valley/Great Lakes region by D5/Saturday. The strength and location of the surface low associated with this cyclone development will play a major role in determining the severe weather potential across the Southeast on D4/Friday. Thunderstorms will likely be ongoing along a front extending southwestward from a surface low over eastern OK. Primary concern is the character of the airmass once this line reaches the Lower MS Valley during the afternoon. A deeper and more southerly surface low could contribute to both more favorable low-level moisture and stronger, more southerly low-level flow. Those conditions would then likely support a reinvigoration of the ongoing line or new development within the warm sector ahead of the line. The most recent GFS shows an intense low-level jet over a large portion of LA and MS, with conditions favorable for supercells. CSU machine-learning probabilities have picked up on these favorable conditions and currently suggest a high probability of severe thunderstorms from northern LA across northern/central MS into Middle TN. However, recent guidance for the ECMWF and CMC does not match the intensity of the low-level jet from the GFS. Additionally, these models have shown more run-to-run consistency over the past few days. Severe thunderstorms are still possible across the Lower MS Valley into the Southeast and Mid-South on Friday, but all of the factors mentioned above preclude introducing higher severe probabilities with this outlook. The cold front will likely continue eastward through the Mid-Atlantic and coastal Southeast on D5/Saturday, but severe potential is expected to be limited by modest buoyancy. Moisture return is anticipated across central/east TX and the Lower MS Valley on D6/Sunday, ahead of another shortwave expected to move through the central Plains. Questions regarding the northern extent of the moisture return and displacement between the buoyancy and lift limit the predictability at this forecast range. ...Mosier.. 03/21/2023 = = = 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) .