Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Sep 21 2023 18:28:25 ACUS03 KWNS 211828 SWODY3 SPC AC 211827 Day 3 Convective Outlook AMEND 1 NWS Storm Prediction Center Norman OK 0127 PM CDT Thu Sep 21 2023 Valid 231200Z - 241200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL/SOUTHERN PLAINS INTO PARTS OF MO/IA/SOUTHERN MN... AMENDED TO ADD SEVERE PROBABILITIES OVER THE COASTAL MID-ATLANTIC ....SUMMARY... Severe thunderstorms are possible on Saturday across parts of the central and southern Plains into Iowa and Missouri. ....Coastal Mid-Atlantic... Recently issued track of Potential Tropical Cyclone 16 brings it onshore over coastal NC early Saturday morning, and then northward into the Chesapeake Bay by Saturday evening. Recent guidance suggests the warm sector to the north and east of the system's center should penetrate far enough inland to support modest buoyancy and deeper convective cores. Given the strong low to mid-level wind fields, any updrafts that are able to deepen and mature could produce tornadoes. Mesoscale details, in particular how much buoyancy develops inland, remain uncertain enough to introducing only a Marginal/Level 2 risk with this amendment. -- PREVIOUS DISCUSSION -- ....Great Plains into parts of MN/IA/MO... A seasonably strong mid/upper-level cyclone is forecast to move eastward across SD on Saturday. The primary surface low attendant to this mid/upper cyclone is forecast to move from the central Plains into the Dakotas as the system begins to occlude, while secondary surface low development is possible along the trailing front across the southern Plains. Moderate to locally strong buoyancy is expected to develop across a broad area of the Great Plains on Saturday, east of the cold front and outside of any areas where outflow persists from morning convection. One notable midlevel jet maximum is forecast to move from the central Plains into the Dakotas, while a southern-stream jet maximum will begin to impinge upon parts of the southern Plains. Organized convection will be possible Saturday into Saturday night across a broad region from the Great Plains into parts of MN/IA/MO, with a mixture of supercells and organized clusters possible along/east of a cold front. Initial development is most likely closer to the mid/upper-level low across the central/northern Plains, with storm development into parts of the southern Plains expected by early Saturday evening. All severe hazards will be possible, though primary storm mode and evolution of mesoscale details remain uncertain at this forecast range. ....Eastern NC into the Mid Atlantic... A surface low is forecast to move from near or just offshore of eastern NC into parts of the Mid Atlantic on Saturday. Depending on the westward extent of the track, richer low-level moisture may spread into coastal areas of the Mid Atlantic region, potentially accompanied by increasing low-level flow/shear and some threat for a brief tornado or two. Depending on the ultimate track and intensity of this system, severe probabilities may eventually be needed for some part of this region. ...Mosier/Dean.. 09/21/2023 $$ = = = 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) .