IEM Daily Bulletin for May 5 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 05 May 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
May 4 8:29 AM	iem,main	📝 Sundry updates per log review	Link
May 4 8:34 AM	iem,main	🐛 Account for unsupported zip+MTR request closes #1607	Link
May 4 8:48 AM	iem,main	🎨 Use json_response_dict and more robust res count	Link
May 4 9:06 AM	iem,main	💚 Address codereview	Link
May 4 10:03 PM	iem,main	✨ Add day ob overlay to dwpf by drct autoplot https://mesonet.agron.iastate.edu/plotting/auto/?q=79	Link
May 4 10:13 PM	iem,main	🐛 Only plot valid MOS + Obs combos https://mesonet.agron.iastate.edu/plotting/auto/?q=37	Link
May 4 10:20 PM	iem,main	🎨 Tighten up time query per codereview	Link

Daily Feature

Chilly Saturday Morning
Date: 04 May 05:30 AM
Votes: Good: 10   Bad: 1 Abstain: 0

After a chilly start to Saturday morning, temperatures quickly recovered and made for an excellent weekend to start off May. How cold it got Saturday morning is the subject of today's featured map displaying computed NCEP RTMA minimum temperature between 3 and 8 AM. So-called local micro-climates can introduce a fair bit of uncertainty into a map like this as subtle topographic and soil type differences can cause major differences in temperature over short distances. Normally, such an event on the second day of May would not be of much concern, but as was mentioned by the daily feature a few days ago, the significant early season warmth has gotten vegetation off on an early start and early May freeze events will continue to be of concern.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 4 May 2026 - 12 AM 5 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	55	6	0	12	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:  54 Verified:  16 [29.6%]
Polygon Size Versus County Size            [29.2%]
Average Perimeter Ratio                    [35.9%]
Percentage of Warned Area Verified (15km)  [14.0%]
Average Storm Based Warning Size           [1077 sq km]
Probability of Detection(higher is better) [0.77]
False Alarm Ratio (lower is better)        [0.70]
Critical Success Index (higher is better)  [0.27]

IEMBot Social Media Posts

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