Severe Storm Outlook Narrative (AC)
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Issued by NWS
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768 ACUS01 KWNS 151242 SWODY1 SPC AC 151240 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0740 AM CDT Sat Jun 15 2024 Valid 151300Z - 161200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL PLAINS/MIDDLE MO VALLEY AND NORTHERN HIGH PLAINS... ...SUMMARY... Scattered severe thunderstorms with damaging winds and large hail are possible from the late afternoon into the evening across the Mid-Missouri Valley and also from eastern Montana to central North Dakota. A couple of tornadoes could occur in eastern Nebraska and western Iowa, with isolated significant severe hail and wind possible across parts of the northern Great Plains. ...Eastern Nebraska to Iowa/northwest Missouri/southern Minnesota... An MCS has largely weakened and trended downscale overnight as it has progressed eastward across western Iowa/northwest Missouri, with outflow extending from these areas west-southeastward into northeast Kansas in proximity to a synoptic stationary/warm front. At least one MCV is evident across the Siouxland vicinity early this morning, with an additional MCV across west-central Nebraska. The aforementioned front will move north-northeastward toward parts of eastern Nebraska and western Iowa today. 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/southwest of the front. As a mid/upper-level trough (with multiple embedded vorticity maxima) approaches the Middle Missouri Valley, and MLCINH diminishes during the afternoon, isolated to widely scattered thunderstorm development will be possible, especially across east/southeast Nebraska and western Iowa and perhaps far northwest Missouri. Along and immediately north of the front, favorable instability, seasonably strong MCV-aided low-level flow, and a favorably veered wind profile in the lowest 3 km AGL will be favorable for tornadic supercells. Rather modest/somewhat backed mid-level flow may result in a tendency for a cluster or complex HP storm mode with time. Any supercells that can be sustained within this regime could pose a tornado threat, in addition to hail and damaging-wind potential. Some modest upscale growth will be possible later in the storm evolution, which could result in a threat for damaging winds and possibly a line-embedded tornado or two spreading east-northeastward into parts of central Iowa and southern Minnesota this evening. ...Northern Great Plains including Eastern Montana and Dakotas... A strong mid/upper-level shortwave trough will move over the Pacific Northwest and northern Rockies later today, and approach the northern High Plains tonight. A surface cyclone will deepen near the Montana/Wyoming border vicinity 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 Montana 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 portions of Montana and Wyoming 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 Montana into western North Dakota. Isolated significant severe gusts will also be possible, especially in areas where stronger heating/mixing occurs, and also in association with any more organized quasi-linear upscale growth. A tornado or two could also occur, especially if any supercell across western North Dakota can be sustained into the evening, when an increase in low-level flow/SRH is expected. ...Southern High Plains... Isolated to widely scattered thunderstorms are expected to develop from mid-afternoon through early evening across parts of the southern High Plains, including the Oklahoma/Texas Panhandles southward to the Permian Basin/Transpecos. Moderate buoyancy and marginally favorable deep-layer shear could support a couple of modestly organized storms. Isolated severe wind gusts will be possible within a generally hot and well-mixed environment, along with some potential for hail. ..Guyer/Leitman.. 06/15/2024 $$