IEM Daily Bulletin for Apr 23 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 23 April 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Apr 22 10:08 PM	iem,main	🐛 Raise Exception before sending response headers	Link

Daily Feature

9 to 5 Temp Changes
Date: 22 Apr 05:30 AM
Votes: Good: 11   Bad: 1 Abstain: 2

Temperatures started off warm Tuesday morning and warmed into the 80s for almost all of Iowa. For Des Moines, the warm-up was 21 degrees between a 9 AM temperature of 63°F to a 5 PM temperature of 84°F (hourly obs listing. The featured chart takes a bit of a deep dive into air temperature changes between 9 AM and 5 PM based on hourly Des Moines airport data. The chart partitions the data by week of the year and plots the frequency of a given temperature change. Negative values indicate a cooler 5 PM temperature than 9 AM of the same day. Values plotted in tan indicate no observations at the given temperature change and week combination. The dashed line is a 14 day smoothed climatology and blue line are 2026 observations, also smoothed to reduce daily noise. The highest frequencies are shown during the summer months when elevated humidity levels reduce temperature variability. The fall season has the largest heating values on average as residual soil warmth from summer and decreased humidity allow for stronger daytime heating.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 22 Apr 2026 - 12 AM 23 Apr 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	28	0	0	0	0	0	0	0
Flash Flood	0	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:  28 Verified:  13 [46.4%]
Polygon Size Versus County Size            [27.4%]
Average Perimeter Ratio                    [17.6%]
Percentage of Warned Area Verified (15km)  [16.2%]
Average Storm Based Warning Size           [2794 sq km]
Probability of Detection(higher is better) [0.32]
False Alarm Ratio (lower is better)        [0.54]
Critical Success Index (higher is better)  [0.24]

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