IEM Daily Bulletin for Jul 17 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 17 July 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Jul 16 8:07 AM	iemvtec,main	🎨 Use new window opener refs #60	Link
Jul 16 8:08 AM	iemvtec,main	🎨 Ignore .vscode	Link
Jul 16 8:08 AM	iemvtec,main	⬆️ Run npm update	Link
Jul 16 8:19 AM	pywwa,main	📝 Add CFC8 pirep	Link
Jul 16 8:19 AM	pywwa,main	⬆️ Update precommits	Link

Daily Feature

Flash Flood Emergencies
Date: 16 Jul 05:30 AM
Votes: Good: 8   Bad: 0 Abstain: 2

The last half of the summer season often features slow moving thunderstorm complexes fed by ample amounts of atmospheric moisture and instability. Flash Flooding is a typical result with rain amounts exceeding rates that the landscape can manage. The main warning headline that the National Weather Service (NWS) has for this situation is the Flash Flood Warning. A messaging escalator that the NWS has is to tag especially dangerous flooding as a Flash Flood Emergency. Two such warnings were issued in Texas yesterday and one last week in Missouri. The IEM attempts to curate a list of these emergencies with the featured screenshot from the online tool that presents them on a map along with a tabling listing. A link to the raw data is available as a GeoJSON on the page or you can use the regular download portal to request a filtered dataset including just these events.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 16 Jul 2026 - 12 AM 17 Jul 2026 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	25	0	0	0	0	0	0	0
Svr Tstorm	77	0	0	0	0	0	0	1
Flash Flood	92	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: 100 Verified:  35 [35.0%]
Polygon Size Versus County Size            [13.5%]
Average Perimeter Ratio                    [13.8%]
Percentage of Warned Area Verified (15km)  [27.7%]
Average Storm Based Warning Size           [1227 sq km]
Probability of Detection(higher is better) [0.80]
False Alarm Ratio (lower is better)        [0.65]
Critical Success Index (higher is better)  [0.32]

IEMBot Social Media Posts

IEMBot can be configured to post messages to a number of social media services. More details: IEMBot Homepage.

Posts yesterday per supported service:

• ATMosphere (bluesky only attm): 2,392
• Mastodon / Fediverse: 11
• Slack: 1,775
• Twitter/X: 9,746
• HTTP Webhooks: 104
• Weather.IM Jabber Chatrooms: 12,996