IEM Daily Bulletin for Jun 27 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 27 June 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Jun 26 7:56 AM	iem,main	🎨 Use die405 and sundry cleanups	Link
Jun 26 8:28 AM	iem,main	💚 Address codereview	Link
Jun 26 8:49 AM	iem,main	💚 Address codereview	Link
Jun 26 12:57 PM	iem-database,main	⬆️ Update ruff precommit	Link
Jun 26 12:58 PM	iem-database,main	🧪 Add scenario0 test CLI file for dep	Link
Jun 26 1:02 PM	iem-database,main	✏️ Fix typo	Link

Daily Feature

Warm End to June
Date: 26 Jun 05:30 AM
Votes: Good: 8   Bad: 1 Abstain: 6

Our current stretch of very pleasant June temperatures is about to abruptly end with much warmer and more humid weather arriving on Sunday and lasting into the start of July, at least. While the IEM website does not offer much for forecast information, there are a few tool and archive resources regarding Model Output Statistics (MOS). The featured chart combines time lagged ensembles of National Blend of Models (NBM) extended (NBE) temperature output for Des Moines along with computed observations attempting to replicate the time periods that the MOS provides forecasts for. Rewording, the MOS does not produce calendar day high and low temperatures, but max and min values over specified time periods within the UTC timezone. Nothing can be easy, can it? Anyway, these values are typically also the calendar day high and low temperature, but not always! The bars represent the range of forecast values when you combine previous MOS outputs containing a forecast for the given date. The dots are the observed "verification". The last three days of June are shown to have significantly warmer high and low temperatures than what we have enjoyed for practically the entire month!

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 26 Jun 2026 - 12 AM 27 Jun 2026 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	7	0	0	0	0	0	0	1
Svr Tstorm	198	0	0	0	0	0	0	5
Flash Flood	41	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: 199 Verified:  51 [25.6%]
Polygon Size Versus County Size            [20.5%]
Average Perimeter Ratio                    [22.1%]
Percentage of Warned Area Verified (15km)  [10.6%]
Average Storm Based Warning Size           [1820 sq km]
Probability of Detection(higher is better) [0.71]
False Alarm Ratio (lower is better)        [0.74]
Critical Success Index (higher is better)  [0.23]

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