IEM Daily Bulletin for Jun 28 2025

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 28 June 2025

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Jun 27 7:12 AM	iem,main	🧐 Tighten up cache expiration	Link
Jun 27 7:41 AM	iem,main	📝 Address some javascript lint	Link
Jun 27 7:44 AM	iem,main	🔥 Drop now-erroring groupmap flag	Link
Jun 27 7:55 AM	iem,main	💚 Address some deepsource lint	Link
Jun 27 7:56 AM	iem,main	[pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci	Link
Jun 27 8:13 AM	iem,main	💚 Appease precommit.ci	Link

Daily Feature

June Temps + Overcast Skies
Date: 27 Jun 05:30 AM
Votes: Good: 4   Bad: 0 Abstain: 0

Today's featured chart looks into the frequency of having overcast skies at a given air temperature during June using period of record observations from the Des Moines Airport. It is always interesting when clear signals are found within plots like this one, but there is sometimes a quirk that is difficult to explain. The easy to explain signal is the decreasing frequency of overcast reports as the temperature increases into the mid 90s. Sunshine during June is certainly important to drive higher air temperatures and conversely cloud free skies to help support the most intense radiational cooling overnight events, but what is happening with the slight increase oin overcast frequency starting in the mid 90s? This likely has to do with the juxtaposition of these extremely warm temperatures only happening during the late afternoon hours and that such warm temperatures are likely driving developing thunderstorm activity off to the west, which increases overcast conditions as the clouds spread east aloft. For this weekend, mostly clear skies are forecast for Saturday with highs in the lower 90s.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 27 Jun 2025 - 12 AM 28 Jun 2025 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	16	0	0	0	0	0	0	1
Svr Tstorm	222	0	0	0	0	1	9	4
Flash Flood	53	0	0	0	0	0	1	---

ARX = LaCrosse, WI DVN = Davenport, IA DMX = Des Moines, IA OAX = Omaha, NE FSD = Sioux Falls, SD

IEM Cow Report

SVR+TOR Warnings Issued: 230 Verified:  75 [32.6%]
Polygon Size Versus County Size            [21.1%]
Average Perimeter Ratio                    [23.4%]
Percentage of Warned Area Verified (15km)  [15.9%]
Average Storm Based Warning Size           [1242 sq km]
Probability of Detection(higher is better) [0.71]
False Alarm Ratio (lower is better)        [0.67]
Critical Success Index (higher is better)  [0.29]