IEM Daily Bulletin for Jun 20 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 20 June 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Jun 19 9:44 AM	iem,main	🚚 Use HRRR gempak files for various plots	Link
Jun 19 10:01 AM	iem,main	🐛 Address sounding autoplot tweaks per 18z flights	Link
Jun 19 10:02 AM	iem,main	⬆️ Update ruff precommit	Link
Jun 19 10:25 AM	iem,main	🚚 Migrate MW Mesoplot to bash	Link
Jun 19 11:01 AM	iem,main	📝 Improve MW mesoplot size and label	Link
Jun 19 11:06 AM	iem,main	🔥 Discontinue lame RWIS/ASOS GEMPAK winds plot	Link
Jun 19 11:20 AM	iem,main	🚚 Migrate from csh to bash	Link
Jun 19 11:45 AM	iem,main	♻️ Merge gempak nexrad + surface plots scripts	Link
Jun 19 12:03 PM	iem,main	🎨 Add beautysh precommit	Link
Jun 19 12:13 PM	iem,main	💚 Address codereview	Link
Jun 19 12:14 PM	iem,main	[pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci	Link
Jun 19 12:50 PM	iem,main	🎨 Finish csh to bash migration	Link
Jun 19 1:05 PM	iem,main	💚 Address codereview	Link
Jun 19 1:09 PM	iem,main	💚 Address more codereview	Link
Jun 19 1:12 PM	iem,main	✏️ Fix typo	Link
Jun 19 1:14 PM	iem,main	🐛 Fix invalid GDPFUN	Link
Jun 19 1:25 PM	iem,main	🎨 Prevent incomplete purpleair data from erroring	Link
Jun 19 1:56 PM	iem,main	🎨 Continue bash script improvements	Link
Jun 19 2:08 PM	iem,main	🐛 Persist fhour between scripts	Link
Jun 19 2:59 PM	iem,main	🔥 Delete cruft	Link

Daily Feature

29°F Dew Point Rise
Date: 19 Jun 05:30 AM
Votes: Good: 9   Bad: 0 Abstain: 0

While near surface air temperature can fluctuate significantly within a day or even day to day, the fluctuations in dew point are typically much lower as processes changing atmospheric water content are slower acting. Dew point changes during the summer season are even more muted as vegetation and available surface/soil water elevate lower atmospheric moisture content. A large change in dew point happened over much of Iowa on Wednesday with seasonally dry air on Tuesday replaced with more typical humid air just 24 hours later. For Cedar Rapids, the dew point temperature increased by 29 degrees Fahrenheit over a 24 hour period. The featured chart presents the largest such dew point increases during the summer months for the site. The recent event comes in first place and joins another Jun 2026 event within the top 10 largest increases! This has been a somewhat frequent pattern this warm season with mostly drier than average air being briefly replaced by more typical humid conditions. Dew point temperatures on Thursday were back again to below average values as drier air from the northwest visited the state.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 19 Jun 2026 - 12 AM 20 Jun 2026 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	9	0	0	0	0	0	0	0
Svr Tstorm	99	0	5	0	0	0	0	1
Flash Flood	59	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: 108 Verified:  41 [38.0%]
Polygon Size Versus County Size            [17.5%]
Average Perimeter Ratio                    [24.4%]
Percentage of Warned Area Verified (15km)  [21.1%]
Average Storm Based Warning Size           [1270 sq km]
Probability of Detection(higher is better) [0.77]
False Alarm Ratio (lower is better)        [0.62]
Critical Success Index (higher is better)  [0.34]

IEMBot Social Media Posts

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