September 3–10, 2026 Storm Activity Digest – Hail Canvass Guide

Week in Review

StormSnipe recorded 15 radar-detected hail events across Montana, North Dakota, Colorado, Nebraska, and Wisconsin from September 3–10, 2026. Total addresses flagged by our radar-derived footprints and verification layers: 17,808. Event hail diameters ranged from 1.00 inch to 3.85 inches. The largest measured radar-derived hail size was 3.85 inches at Arnegard, North Dakota on September 7, 2026. The largest address impacts were Hartford, Wisconsin (3.75 inch hail, 8,072 addresses) and Alliance, Nebraska (3.75 inch hail, 4,274 addresses, spotter-verified).

Summary statistics

• Events: 15
• Total addresses affected: 17,808
• Maximum radar-derived hail diameter: 3.85 inches (Arnegard, ND, Sep 7)
• Highest single-event address counts: Hartford, WI – 8,072 addresses (Sep 4); Alliance, NE – 4,274 addresses, spotter-verified (Sep 5)
• Date concentration: Sep 4 and Sep 7 had the most significant activity by address count

Notable Events

All events listed with town, state, date, radar-derived hail diameter, addresses affected, and detection method.

• Zortman, MT – 2026-09-07 – 3.25 inches hail – 14 addresses – dual-polarization radar
• Killdeer, ND – 2026-09-07 – 3.52 inches hail – 36 addresses – dual-polarization radar
• Haswell, CO – 2026-09-10 – 3.35 inches hail – 0 addresses – dual-polarization radar
• Hartford, WI – 2026-09-04 – 3.75 inches hail – 8,072 addresses – dual-polarization radar
• Alliance, NE – 2026-09-05 – 3.75 inches hail – 3 addresses – radar + spotter-verified
• Alliance, NE – 2026-09-05 – 3.75 inches hail – 4,274 addresses – radar + spotter-verified
• Broadwater, NE – 2026-09-06 – 2.50 inches hail – 2 addresses – dual-polarization radar
• Walsenburg, CO – 2026-09-10 – 3.06 inches hail – 3 addresses – dual-polarization radar
• Winifred, MT – 2026-09-07 – 3.73 inches hail – 1 address – dual-polarization radar
• Scandinavia, WI – 2026-09-04 – 2.75 inches hail – 2,964 addresses – dual-polarization radar
• Hartford, WI – 2026-09-04 – 3.75 inches hail – 592 addresses – dual-polarization radar
• Arnegard, ND – 2026-09-07 – 3.85 inches hail – 1,834 addresses – dual-polarization radar
• Roy, MT – 2026-09-07 – 2.37 inches hail – 10 addresses – dual-polarization radar
• Bridgeport, NE – 2026-09-06 – 2.50 inches hail – 0 addresses – dual-polarization radar
• Mandaree, ND – 2026-09-07 – 1.00 inch hail – 3 addresses – dual-polarization radar

Field verification note

Alliance, Nebraska on September 5 had two radar-derived footprints tied to spotter-verified reports. Both showed 3.75 inch hail. One footprint covered 4,274 addresses and one covered 3 addresses. Use the spotter-verified event as higher confidence for on-the-ground severe asset exposure.

Regional Patterns

Northern Plains and Upper Midwest concentration

• North Dakota and Montana produced the largest hail diameters by measurement on September 7. Arnegard, ND recorded the peak diameter at 3.85 inches. Killdeer, ND and multiple Montana towns also exceeded 3.25 inches on the same day.

• Wisconsin activity on September 4 produced the largest address-level impacts. Hartford had two radar-derived footprints of 3.75 inch hail covering 8,072 and 592 addresses. Scandinavia, WI recorded 2.75 inch hail and 2,964 addresses. These three footprints account for the largest share of week-long address exposure.

Nebraska and Colorado events

• Alliance, NE on September 5 produced a spotter-verified 3.75 inch event with 4,274 addresses, plus a separate small 3-address footprint with the same diameter. Bridgeport and Broadwater, NE recorded 2.50 inch footprints on September 6.

• Colorado entries on September 10 were Haswell (3.35 inches, 0 addresses) and Walsenburg (3.06 inches, 3 addresses). These were isolated radar-derived detections with limited residential exposure.

Temporal clustering

• September 7 accounted for the highest number of large-diameter detections across MT and ND, suggesting a single synoptic pulse produced multiple severe cores across the Northern Plains. September 4 produced the largest address-level impacts concentrated in eastern Wisconsin.

What Contractors Should Watch

Prioritization guidance

• Immediate canvass candidates: Hartford, WI (Sep 4) and Alliance, NE (Sep 5 spotter-verified footprint of 4,274 addresses). These three Wisconsin footprints and the large Alliance footprint represent the highest address volumes this week. Allocate initial canvass crews and triage teams to these areas first.

• Secondary canvass: Scandinavia, WI (2,964 addresses) and Arnegard, ND (1,834 addresses). Plan scaled inspections for these areas within the first 7 business days after the event.

• Low-exposure, high-severity detections: Arnegard, Killdeer, Winifred, and Zortman recorded hail >3.25 inches but impacted fewer addresses. Route at least one experienced estimator to each to confirm roof-level impacts and prioritize tarping where active leaks are reported.

Operational notes

• Use spotter-verified events to raise inspection priority. Alliance, NE had spotter confirmation for 3.75 inch hail and the larger footprint. Spotter verification correlates with higher confidence in ground damage potential.

• Address counts indicate canvass scale. Hartford's 8,072-address footprint will require multiple teams and a staging plan for documentation and temporary repairs. Scandinavia's 2,964-address footprint requires a mid-sized canvass response.

• Zero-address radar detections (Haswell, Bridgeport) still warrant a targeted check of critical commercial assets, municipal facilities, and insurance claims in rural catchments if customer reports arrive.

Documentation and safety

• For any rooftop work, confirm municipal permits and safety plans before deploying crews. Record hail diameters, photos of hail, and photo-tagged damage for each inspected address.

Forward-looking note

Model runs for the coming week show a diminishing closed upper-level trough and a more zonal flow pattern. Shortwave energy remains forecast to pass through the northern tier by midweek, increasing instability across the Northern Plains. Contractors should maintain readiness for isolated severe hail chances from Sep 11–17, with the highest conditional risk over eastern Montana into western North Dakota. Monitor updated radar-derived footprints and spotter reports for new address-level exposure.