Scattered severe thunderstorms with damaging winds and large hail are possible from late afternoon into the evening across the mid-Missouri Valley and 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. Further south, high-based storms with damaging winds and some hail are possible in the Oklahoma/Texas Panhandles into West Texas.

Locations:

  • Primary Risk Area: Northern Plains, most especially western North Dakota.
  • Secondary Risk Area: Eastern Nebraska into Iowa
  • The Other Risk Area: Oklahoma/Texas Panhandles into West Texas

Threats:

  • Damaging Winds: A threat with storms border to border.
  • Large Hail: Most likely across the Central Plains and Northern High Plains.
  • Tornadoes: A couple of tornadoes could occur in the primary and secondary risk areas.

Timing:

  •  Storm Initiation: Late afternoon.
  •  Peak Threat: Late afternoon into the evening.
  •  Storm Weakening: Overnight, as storms move eastward.

Discussion:

Eastern Nebraska to Iowa/Northwest Missouri/Southern Minnesota:

  • Setup: An MCS has weakened overnight across western Iowa/northwest Missouri. Outflow extends into northeast Kansas, near a stationary/warm front. MCVs are evident across Siouxland and west-central Nebraska.
  • Storm Development: The front will move north-northeastward today. Diurnal heating will support moderate to strong destabilization. As a mid/upper-level trough approaches the middle Missouri Valley, isolated to widely scattered thunderstorms are possible, especially across east/southeast Nebraska and western Iowa.
  • Severe Potential: Favorable instability and low-level flow will support tornadic supercells, especially near the front. A cluster or complex HP storm mode may develop, with potential for tornadoes, large hail, and damaging winds. Modest upscale growth may result in a threat for damaging winds and possibly line-embedded tornadoes into central Iowa and southern Minnesota this evening.

Northern Great Plains (Eastern Montana and Dakotas):

  • Setup: A strong mid/upper-level shortwave trough will move over the Pacific Northwest and northern Rockies, approaching the northern High Plains tonight. A surface cyclone will deepen near the Montana/Wyoming border, moving northeastward across the western Dakotas this evening.
  • Storm Development: MLCAPE is forecast to increase to 1500-2500 J/kg from eastern Montana into the Dakotas. Strong deep-layer flow/shear will begin impinging on the warm sector by late afternoon.
  • Severe Potential: Storms will develop by late afternoon from eastern Montana and Wyoming into the western Dakotas. Large to very large hail could accompany any sustained supercells, especially from eastern Montana into western North Dakota. Isolated significant severe gusts are also possible, particularly with stronger heating/mixing and organized quasi-linear upscale growth. A tornado or two could occur, especially if any supercell across western North Dakota can be sustained into the evening when low-level flow/SRH increases.

Southern High Plains:

  • Setup: Isolated to widely scattered thunderstorms are expected from mid-afternoon through early evening across parts of the southern High Plains, including the Oklahoma/Texas Panhandles southward to the Permian Basin/Transpecos.
  • Severe Potential: Moderate buoyancy and marginally favorable deep-layer shear could support a couple of modestly organized storms. Isolated severe wind gusts and hail are possible within a generally hot and well-mixed environment.