Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
079 ACUS03 KWNS 240731 SWODY3 SPC AC 240730 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Fri May 24 2024 Valid 261200Z - 271200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SUNDAY INTO SUNDAY NIGHT ACROSS PARTS OF SOUTHEASTERN IOWA...EASTERN MISSOURI...MUCH OF CENTRAL AND SOUTHERN ILLINOIS...MUCH OF CENTRAL AND SOUTHERN INDIANA...WESTERN AND CENTRAL KENTUCKY... ...SUMMARY... Severe thunderstorms are likely Sunday into Sunday night across parts of the middle Mississippi and lower Ohio Valleys. ...Synopsis... Models indicate that initially low-amplitude mid-level troughing, comprised of at least a couple smaller-scale perturbations emerging from the Great Basin and Southwest, will progress northeast and east of the lower Missouri Valley and central Great Plains during the day Sunday. It appears that this will be accompanied by notable further deepening of a relatively compact developing cyclone across the lower Missouri Valley through the Upper Great Lakes region by late Sunday night. There may also be a gradual consolidation of mid-level troughing centered over the Mississippi Valley, within amplifying flow across the northern mid-latitudes of the eastern Pacific through North America. ...Southeastern Great Lakes through Ohio Valley/Great Lakes... Given the large potential instability associated with low-level moisture return through the warm sector of the developing cyclone, beneath at least initially capping elevated mixed-layer air, strong to severe thunderstorm development may accompany mid-level height falls across a potentially sizable area of the interior U.S. The details of this evolution remain uncertain, due spread within/among the model output concerning the synoptic and sub-synoptic developments, which may include one or two substantial clusters of convective development across the lower Missouri Valley at the outset of the period. At the present time, model output seems suggestive that the most probable convective evolution may include early period convection weakening while spreading across and east of the middle Mississippi Valley during the day. In its wake, a corridor of strengthening differential surface heating may develop along the western flank of modifying convective outflow across parts of the lower Ohio Valley northwestward through the middle Mississippi Valley. By Sunday afternoon, renewed convective development may focus near the intersection of the outflow and a southward advancing cold front across the west central Illinois/northeastern Missouri vicinity. Supported by large mixed-layer CAPE and strong shear, the environment likely will be conducive to supercells initially, before low-level warm advection along the remnant outflow supports an upscale growing cluster which should tend to forward propagate southeastward across the lower Ohio into Tennessee Valley through Sunday evening. While convection may gradually increase along the southward advancing front to the southwest of the outflow boundary, the outflow boundary/differential heating zone seems likely to become the focus for the primary severe weather hazards, including a large hail/supercell tornado risk to damaging winds and perhaps a continuing QLCS tornado threat. ..Kerr.. 05/24/2024 $$