IEM Daily Bulletin for Dec 20 2025
daryl herzmann
Iowa Environmental Mesonet Daily Bulletin for 20 December 2025
News
No news is good newsIEM Code Pushes <repo,branch> on Github
| Timestamp | Repository | Message | Link |
|---|---|---|---|
| Dec 19 8:16 AM | iem,main | 🎨 Simplify error logging | Link |
| Dec 19 8:17 AM | iem,main | ⬆️ Update precommits | Link |
| Dec 19 3:14 PM | iem,main | 📝 Update to https | Link |
Daily Feature
'25-'26 Winter Storm #8
Date: 19 Dec 08:05 AM
Votes: Good: 13
Bad: 0 Abstain: 0
It did not take much snow to cause major problems Thursday afternoon over northern Iowa and other isolated parts of the state. The featured map shows a smoothed analysis of available snowfall reports, which generally were a tenth of an inch or less! The counties outlined in red had a Blizzard Warning active sometime during the afternoon hours. Brief and intense snow squalls combined with very strong winds to create rapidly varying visibility and road conditions leading to many multi-vehicle accidents and subsequent road closures. Rainfall earlier in the day likely did not help either as it washed away road treatments and created some icy spots when temperatures rapidly dropped with the frontal passage. Other areas in the state outside of the highlighted Blizzard Warning and measurable snowfall area experienced some isolated travel issues with brief snow squalls.
NWS Watch/Warning Summary for 12 AM 19 Dec 2025 - 12 AM 20 Dec 2025 CST
| Summary | By WFO | Watches | ||||||
|---|---|---|---|---|---|---|---|---|
| Type | US | IA | ARX | DVN | DMX | OAX | FSD | US |
| Tornado | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Svr Tstorm | 15 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Flash Flood | 1 | 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: 16 Verified: 12 [75.0%] Polygon Size Versus County Size [57.1%] Average Perimeter Ratio [21.4%] Percentage of Warned Area Verified (15km) [26.1%] Average Storm Based Warning Size [4809 sq km] Probability of Detection(higher is better) [0.71] False Alarm Ratio (lower is better) [0.25] Critical Success Index (higher is better) [0.57]