Iowa Environmental Mesonet Daily Bulletin for 10 October 2026

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Daily Feature

October Surprise
Date: 09 Oct 05:30 AM
Votes: Good: 15   Bad: 0 Abstain: 0

The strong storms that developed early Thursday evening over Iowa were a bit of a forecast surprise with only very late runs of various forecast models depicting a possible robust environment to produce elevated thunderstorms capable of large hail. The NWS issued a number of warnings for the event and got hail reports to verify those warnings. The featured chart looks into the time of day frequency of having Severe Thunderstorm Warnings during the month of October. The chart presents the time of day frequency for Des Moines with the overall frequency plotted in tan and the values for October in blue. Of course, there are much fewer events during October so the plot gets a bit noisy vs the smooth full year values. Having such warnings during the night time is certainly more common than during the day as processes like the nocturnal "Low Level Jet" help fuel thunderstorms overnight.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 9 Oct 2026 - 12 AM 10 Oct 2026 CDT

Summary By WFO Watches
Type USIA ARXDVNDMXOAXFSD US
Tornado 5 0 0 0 0 0 0 2
Svr Tstorm 14 9 0 0 3 0 6 0
Flash Flood 34 1 0 0 0 0 1---

ARX = LaCrosse, WI DVN = Davenport, IA DMX = Des Moines, IA OAX = Omaha, NE FSD = Sioux Falls, SD

IEM Cow Report

SVR+TOR Warnings Issued:  19 Verified:   8 [42.1%]
Polygon Size Versus County Size            [20.5%]
Average Perimeter Ratio                    [14.6%]
Percentage of Warned Area Verified (15km)  [28.9%]
Average Storm Based Warning Size           [767 sq km]
Probability of Detection(higher is better) [0.92]
False Alarm Ratio (lower is better)        [0.58]
Critical Success Index (higher is better)  [0.41]

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