IEM Daily Bulletin for Apr 18 2026
daryl herzmann
Iowa Environmental Mesonet Daily Bulletin for 18 April 2026
News
No news is good newsIEM Code Pushes <repo,branch> on Github
| Timestamp | Repository | Message | Link |
|---|---|---|---|
| Apr 17 1:32 PM | iem,main | 🐛 Fix returned threshold value | Link |
| Apr 17 10:06 PM | iem,main | 🐛 Properly compute axis max | Link |
| Apr 17 8:04 AM | pyiem,main | ⬆️ Update precommits | Link |
| Apr 17 8:12 AM | pyiem,main | 🔨 [SHEF] include `:` in element narrative | Link |
| Apr 17 8:19 AM | pywwa,main | 📝 Update precommits | Link |
| Apr 17 8:28 AM | pywwa,main | ✨ Persist narrative/comment SHEF to IEMAccess | Link |
| Apr 17 9:15 AM | pywwa,main | 🐛 Correct SQL for persisting SHEF comment | Link |
| Apr 17 7:56 AM | iem-database,main | ⬆️ Update ruff precommit | Link |
| Apr 17 7:58 AM | iem-database,main | ✨ Add current_shef comment storage | Link |
| Apr 17 8:39 AM | iem-web-services,main | ⬆️ Update ruff | Link |
| Apr 17 8:44 AM | iem-web-services,main | ✨ Include comment field from current_shef | Link |
Daily Feature
Active Week Continues
Date: 17 Apr 05:30 AM
Votes: Good: 15
Bad: 0 Abstain: 1
It has been a very active week for severe weather over Iowa. While Thursday was a very welcome break from the rough weather this week, strong thunderstorms are very likely Friday with eastern Iowa that primary target for the worst of the storms. The featured chart presents the daily number of combined Tornado and Severe Thunderstorm Warnings issued by the National Weather Service for counties within Iowa. It is likely that four days for this week will have a higher total of such warnings than any previous day so far this year!
Updated: The featured chart was regenerated to show the Friday total of 74 warnings.
The featured media can be generated on-demand here
.NWS Watch/Warning Summary for 12 AM 17 Apr 2026 - 12 AM 18 Apr 2026 CDT
| Summary | By WFO | Watches | ||||||
|---|---|---|---|---|---|---|---|---|
| Type | US | IA | ARX | DVN | DMX | OAX | FSD | US |
| Tornado | 150 | 31 | 26 | 20 | 8 | 0 | 0 | 4 |
| Svr Tstorm | 304 | 57 | 9 | 30 | 22 | 0 | 0 | 2 |
| Flash Flood | 22 | 1 | 0 | 1 | 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: 448 Verified: 184 [41.1%] Polygon Size Versus County Size [34.8%] Average Perimeter Ratio [37.4%] Percentage of Warned Area Verified (15km) [21.9%] Average Storm Based Warning Size [1750 sq km] Probability of Detection(higher is better) [0.84] False Alarm Ratio (lower is better) [0.59] Critical Success Index (higher is better) [0.38]
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