IEM Daily Bulletin for Mar 13 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 13 March 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Mar 12 9:00 AM	iem,main	📝 Sundry updates per log review	Link
Mar 12 11:38 AM	iem,main	Update VTEC coding descriptions Significance is a single character, and was listed twice. I suspect one of these should be the (3 char) action, though I think it can only be used as a suffix for certain products per the changelog?	Link
Mar 12 1:46 PM	iem,main	🐛 Fix max date specification	Link
Mar 12 7:22 PM	iem,main	📝 Sundry updates per log review	Link
Mar 12 12:41 PM	pyiem,main	⬆️ Update pyproject-fmt precommit	Link
Mar 12 1:00 PM	pyiem,main	🐛 Prevent loading unknown names into CGIModel closes #1174	Link
Mar 12 1:01 PM	pyiem,main	[pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci	Link
Mar 12 10:15 PM	pyiem,main	⚡️ Reduce multiplier	Link

Daily Feature

'25-'26 Winter Storm #19
Date: 12 Mar 08:42 AM
Votes: Good: 10   Bad: 0 Abstain: 0

After severe storms on Tuesday over southeastern Iowa, the backside of the storm system brought a small taste of winter with a brief coating of snow over most of the rest of the state. While not much for a winter storm, there was an isolated two inch snowfall report, so that arbitrary threshold triggers an IEM map with a crude accounting of available NWS and CoCoRaHS snowfall reports. This snow almost immediately melted, so proper measurement and reporting was difficult. The map shows a couple of areas of the state with over an inch of snow from the event. We are not done with winter yet as more snow is in the forecast.

NWS Watch/Warning Summary for 12 AM 12 Mar 2026 - 12 AM 13 Mar 2026 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	39	0	0	0	0	0	0	1
Svr Tstorm	75	0	0	0	0	0	0	1
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: 114 Verified:  54 [47.4%]
Polygon Size Versus County Size            [45.1%]
Average Perimeter Ratio                    [28.5%]
Percentage of Warned Area Verified (15km)  [24.3%]
Average Storm Based Warning Size           [2914 sq km]
Probability of Detection(higher is better) [0.81]
False Alarm Ratio (lower is better)        [0.53]
Critical Success Index (higher is better)  [0.43]

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