Damaging Winds, Large Hail & Isolated Tornadoes Possible; Upper MS Valley; Evening; August 26th 2024

Photo byNational Weather Force

Brief Outlook:

Severe thunderstorms are expected across parts of the Upper Mississippi Valley today, particularly impacting southeastern Minnesota, western Wisconsin, and northeastern Iowa. These storms will be capable of producing damaging winds, large hail, and isolated tornadoes. Check below for further details.

Region Impacted: Upper Mississippi Valley

Upper-Level Dynamics:

An upper-level shortwave trough will move eastward across the northern Plains, leading to the development of strong thunderstorms over the Upper Mississippi Valley. Enhanced mid-level flow, with winds of 40-50 knots, will support the organization of severe storms. These conditions, combined with a strong jet streak, will create an environment favorable for supercells and organized storm clusters.

Surface Conditions:

At the surface, instability values are expected to reach 2500-4000 J/kg across the Upper Mississippi Valley, driven by high temperatures and ample moisture, with dewpoints in the upper 60s to low 70s. Mid-level lapse rates (change in temperature with height) are expected to be moderate to steep, further enhancing the potential for severe weather. The presence of a cold front moving southeastward through the region will serve as the primary trigger for storm initiation. Effective shear will support the development of discrete supercells initially, with the potential for very large hail and isolated tornadoes. As the late evening progresses, storms may merge into larger clusters or lines, with damaging winds sometimes destructive becoming the primary threat.

Timing:

Storms are expected to initiate late afternoon (around 3-4 PM CDT) in southeastern Minnesota and northeastern Iowa, with activity spreading into western Wisconsin overnight. Peak intensity is likely to occur from late afternoon through the evening, with the strongest storms expected during this period of time. As storms continue to progress, they will transition to damaging winds as they move eastward into WI. Storms will be more discrete at first before turning into clusters with an MCS potentially likely.

Main Impact: damaging winds, very large hail, isolated tornadoes and lightning.

Stay tuned for more updates.

Sina⚡⚡

Co-Owner/CTO and Lead Forecaster of NWF Innovations & NWF Networks

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