IEM Daily Bulletin for May 2 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 02 May 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
May 1 8:50 AM	iem,main	⚡️ Tweak query to workaround postgresql planner Updated query makes better usage of indices	Link

Daily Feature

April Flight Rules
Date: 01 May 05:30 AM
Votes: Good: 9   Bad: 2 Abstain: 0

The start of a new month is always a good time to review what happened for the previous month. The featured chart reviews hourly aviation flight rules computed from the Des Moines airport weather station. These rules consider cloud ceilings and horizontal visibility among other things to restrict aviation traffic. The featured chart only considers the weather station horizontal visibility distance and vertical distance to cloud coverage either in "broken" or "overcast" state. The chart is a nice first guess to indicate periods where there was likely poor flying weather conditions due to visibility reductions. The stormy start to April is most noticeable with reductions more isolated after the first few days.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 1 May 2026 - 12 AM 2 May 2026 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	0	0	0	0	0	0	0	0
Svr Tstorm	27	0	0	0	0	0	0	0
Flash Flood	8	0	0	0	0	0	0	---

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

IEM Cow Report

SVR+TOR Warnings Issued:  27 Verified:  11 [40.7%]
Polygon Size Versus County Size            [26.3%]
Average Perimeter Ratio                    [19.2%]
Percentage of Warned Area Verified (15km)  [15.4%]
Average Storm Based Warning Size           [1680 sq km]
Probability of Detection(higher is better) [0.90]
False Alarm Ratio (lower is better)        [0.59]
Critical Success Index (higher is better)  [0.39]

IEMBot Social Media Posts

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