SPC Apr 27, 2024 1300 UTC Day 1 Convective Outlook
2024-04-27
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Sat Apr 27 2024 Valid 271300Z - 281200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THROUGH TONIGHT FOR OK...NORTH TX...SOUTHEAST KS AND EXTREME SOUTHWEST MO... ...SUMMARY... Severe thunderstorms are likely today and tonight across the southern and central Plains into the lower to mid Missouri Valley. The most numerous/intense storms are expected from north Texas into Oklahoma and southeast Kansas, where strong tornadoes, very large hail of 2-3 inches in diameter and damaging winds of 60-70 mph are all possible. ...A regional severe-weather outbreak is expected from north TX across OK into KS with strong tornadoes, very large hail and damaging winds all part of a long-duration threat... ...OK/KS/north TX through tonight... A pronounced midlevel trough over the Four Corners will move eastward today and then begin to eject northeastward tonight over the central/southern High Plains. This synoptic pattern will maintain a lee cyclone in southeast CO and a dryline arcing southeastward and then southward close to the western OK border. Farther north, a stalling baroclinic zone will move slowly northward into northern KS today and central IA by this evening. A broad, unstable warm sector with boundary-layer dewpoints of 65-70 F will support multiple rounds of severe/tornadic storms through the period, both along the synoptic boundaries and in parts of the open warm sector for OK/KS. The initial severe/tornado threat has already begun near Caprock from Lubbock to Childress as an embedded jet streak (evident as the fast-moving cloud streak over west TX) begins to interact with the northwest edge of the richer low-level moisture. Despite the unusually early start, there will be the potential for embedded supercells capable of all hazards as the storms overspread western/northern OK into southern KS through midday. An outflow boundary and/or differential heating corridor is likely in the immediate wake of these morning storms from southern KS into north central and southwest OK. Additional thunderstorm development is likely by early-mid afternoon along this zone and the dryline to the south into TX, and storms will spread generally northeastward toward southern/central OK and southeast KS. A moist boundary layer, MLCAPE of 2500-3500 J/kg and lengthening/enlarging hodographs with time (as a mass response to the approaching shortwave trough) will become more favorable for tornadic supercells, including the potential for long-track EF2-EF3+ tornadoes. The significant tornado threat will be greatest if semi-discrete supercells can be maintained well into the afternoon/evening. Very large hail up to 3 inches in diameter can also be expected with the more intense supercells. The storm evolution has the potential to be a bit messy with multiple training/conjoined supercells, posing a relatively long-duration and repeat threat to areas within the training storm corridors across the central third of OK. Damaging winds will become more probable with storm clustering, and there will likely be upscale growth into a larger QLCS this evening into tonight as the primary shortwave trough approaches from the west. The potential for tornadoes with embedded circulation will continue into the overnight hours, along with damaging winds. ...East central CO/far western KS this afternoon/evening... Near the lee cyclone and a stalled front, thunderstorm development is expected by early afternoon in a small cluster/arc across east central CO. Despite boundary-layer dewpoints only in the 40s, cold midlevel temperatures and steep lapse rates will contribute to surface-based CAPE up to 1000 J/kg. Relatively large, curved hodographs will favor supercells capable of producing a few tornadoes and large hail, as well as damaging gusts once any upscale growth into a line segment occurs. ...Northern IL/southeast WI/Lower MI this afternoon/evening... A midlevel trough and associated surface cyclone will move northeastward today from the upper MS Valley to the upper Great Lakes. The stronger forcing for ascent has already moved northeast of the surface warm sector, so storm development in this corridor will likely be later this afternoon/evening in association with low-level ascent along the stalling front across WI/lower MI. A band of storms is expected along the front, and other convection could eventually spread into northern IL from eastern IA. Forecast profiles along and south of the front show sufficient hodograph length/deep-layer shear for organized line segments and some embedded supercells capable of producing damaging gusts and possibly a tornado or two. Isolated large hail will also be possible, given some potential for embedded supercells within the northeast extent of the 7-8 C/km midlevel lapse rates. ..Thompson/Hart.. 04/27/2024
