ACUS01 KWNS 021951 SWODY1 SPC AC 021949 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0249 PM CDT Sun Jun 02 2024 Valid 022000Z - 031200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NEBRASKA AND NORTHERN KANSAS... ...SUMMARY... Scattered severe thunderstorms are forecast across much of the Plains region this afternoon and evening, especially across the central Plains of Nebraska and northwest Kansas. Very large hail of 2-3 inches in diameter, severe gusts of 60-80 mph, and a couple of tornadoes are expected. ...OK/TX... The Slight (level 2 of 5) and Marginal (level 1 of 5) risk areas have been expanded to the east and south of an ongoing bowing cluster of storms near the Red River and western north TX. These storms are expected to continue shifting east/southeast along an instability gradient amid 35-45 kt 0-6 km west/northwesterly flow. Damaging gusts will be the main hazard with this activity, though large hail is also possible within strongest cells. Tornado probabilities have also been adjusted a small amount in the TX Panhandle based on the 18z AMA RAOB, and across southwest TX based on latest surface observations. ...Northern/Central Plains... No changes have been made to the ongoing outlook. See previous outlook for more details, and latest MCDs for short term severe potential. ..Leitman.. 06/02/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Sun Jun 02 2024/ ...Central Plains through tonight... Considerable uncertainty is apparent in this forecast update due in part to mesoscale-driven convective outflow and its effects on destabilization and quality of the warm sector for later this afternoon and tonight. Within generally zonal flow aloft, a low amplitude shortwave trough will progress eastward from the northern Rockies to the northern Plains through tonight. Lee cyclogenesis is expected across western NE/northeast CO near the southern influence of this midlevel trough, with a weak cold front farther north into the Dakotas. The surface front/cyclone, as well as a lee trough farther to the south will help focus thunderstorm development this afternoon and storms will spread eastward through tonight. Late this morning, several thunderstorm clusters have moved east and weakened across the eastern half of NE and central KS. To the west of the outflow/residual cold pools from this early-day activity, surface temperatures will warm into the 80s with boundary-layer dewpoints mainly in the upper 50s to lower 60s, beneath steep midlevel lapse rates. The net result will be a narrow corridor of large buoyancy (MLCAPE of 2500-4000 J/kg) and minimal convective inhibition by mid afternoon from west TX to NE to the east of the lee trough/dryline, when thunderstorm development is expected. The initial storms in western NE into northwest KS could be supercells capable of producing isolated very large hail (2-3 inches in diameter) and any tornado threat will be tied to the more discrete initial supercells. Eventual upscale growth during the evening will lead to an increasing threat for severe gusts 60-80 mph as this activity develops and moves eastward as a southerly LLJ intensifies. ...Southern High Plains this afternoon into tonight... Similar to the central High Plains, appreciable uncertainty in this forecast due to an ongoing midday thunderstorm cluster over southern OK/north TX (reference MCD #1124 and associated Severe Thunderstorm Watch #372) and its stabilizing influence and ability to focus storm development later this afternoon and tonight. If fresh outflow is able to be reduced and/or become much more displaced from the dryline by mid-late afternoon, it seems plausible the deleterious effects will be minimal from the western TX Panhandle southward along/east of the dryline. At least widely scattered storms are expected by mid-late afternoon along the dryline from the TX Panhandle into west central TX, potentially aided by a mid-level shortwave trough moving east across NM late this morning. Elongated hodographs will favor supercells capable of producing isolated very large hail (2-3 inches in diameter). Any mature supercell able to interact in the vicinity of the modified outflow boundary or within richer low-level moisture over the TX South Plains, will potentially yield a tornado risk. Though storm coverage will be a primary driver of any damaging-wind threat, thermodynamic profiles will favor intense downdrafts capable of producing isolated significant outflow gusts of 75-80 mph. A coalescing of storms during the evening into the overnight may eventually move into northwest TX/western OK before weakening late tonight. ...Northern Plains this afternoon/evening... Not much change from previous forecast thinking in that the warm sector will narrow and buoyancy will weaken with northward extent from SD into ND, ahead of the surface cold front. This front, and ascent related to the approaching midlevel trough, will help focus a line of thunderstorms along the front in central ND by early-mid afternoon (possibly evolving from the ongoing storms near the southwest ND border), and storms will subsequently spread eastward toward western MN in the evening and develop southward into SD. The initial storms, or any embedded supercells, will pose a threat for large hail of 1-1.75 inches in diameter, while damaging gusts of 60-70 mph will become the more common threat once a linear mode is established (and before the storms move too far east of the primary buoyancy corridor). ...Southern LA to central/north TX this afternoon... Scattered thunderstorm development will be possible in a loosely focused corridor from southern LA into parts of southeast, central and north TX along a remnant outflow/returning moisture gradient. Though storm development in any particular area is low confidence, a few storms in this area could pose a threat for isolated large hail/wind damage given large CAPE and sufficient deep-layer shear/hodograph length for at least some supercell potential. $$