Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
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033 ACUS01 KWNS 150600 SWODY1 SPC AC 150558 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Sat Jun 15 2024 Valid 151200Z - 161200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR EASTERN NE/WESTERN IA AND ADJACENT PARTS OF NORTHEAST KS...NORTHWEST MO...SOUTHEAST SD...SOUTHERN MN...AND ALSO FROM EASTERN MT INTO THE WESTERN DAKOTAS... ...SUMMARY... Scattered severe thunderstorms with damaging winds and large hail are possible from the late afternoon into the evening, both across the Mid-Missouri Valley and also from eastern Montana to central North Dakota. A couple of tornadic storms may occur in eastern Nebraska and western Iowa, with isolated significant severe hail and wind possible across parts of the northern Great Plains. ...Eastern NE/northeast KS into western IA... A weakening or decayed MCS will likely be ongoing at the start of the period somewhere from extreme eastern NE into western IA. In the wake of this feature, an outflow-reinforced front will likely begin lifting northward across some part of eastern NE into western IA through the day. Diurnal heating will support moderate to strong destabilization, both within a richly moist environment near/north of the front, and within a somewhat hotter and more well-mixed environment south of the front. As a mid/upper-level trough (with multiple embedded vorticity maxima) approaches the mid MO Valley, and MLCINH diminishes during the afternoon, isolated to widely scattered thunderstorm development will be possible. Along and immediately north of the front, favorable instability, seasonably strong low-level flow, and a favorably veered wind profile in the lowest 3 km will be favorable for tornadic supercells, though rather modest flow above 3 km may result in a tendency for a cluster or complex storm mode with time. Any supercells that can be sustained within this regime would pose a tornado threat, in addition to hail and damaging-wind potential. However, considerable uncertainty remains, both regarding the frontal position during the time of storm initiation, and also the longevity of a more discrete supercell mode. The 5% tornado area has been expanded somewhat to account for the spatial uncertainty. Some modest upscale growth will be possible later in the storm evolution, which could result in a threat for damaging wind and possibly a line-embedded tornado or two spreading east-northeastward into parts of central IA and southern MN during the evening. ...Northern Great Plains... A rather strong mid/upper-level shortwave trough will move across the Northwest and northern Rockies later today, and begin approaching the northern High Plains tonight. A surface cyclone is forecast to deepen near the MT/WY border during the day, and then move northeastward across the western Dakotas vicinity this evening. Near and east of the surface cyclone, MLCAPE is forecast to increase into the 1500-2500 J/kg range from parts of eastern MT into the Dakotas, while stronger deep-layer flow/shear attendant to the approaching shortwave will begin impinging on the warm sector by late afternoon into the evening. Storm development is expected by late afternoon from eastern MT/WY into the western Dakotas, with development of one or more intense storm clusters possible by early evening. Large to very large hail could accompany any sustained supercells within this regime, especially from eastern MT into western ND. Isolated significant severe gusts will also be possible, especially in areas where stronger heating/mixing occurs, and also in association with any more organized upscale growth. A tornado or two will also be possible, especially if any supercell across western ND can be sustained into the evening, when a notable increase in low-level flow/shear will be possible. ...Southern High Plains vicinity... Isolated to widely scattered thunderstorms will be possible this afternoon and evening across parts of the southern High Plains, and also across the higher terrain of southwest TX. Moderate buoyancy and marginally favorable deep-layer shear could support a couple of modestly organized storms. Isolated severe gusts will be possible within a generally hot and well-mixed environment, along with some potential for hail. ..Dean/Thornton.. 06/15/2024 $$