Past Features
This page lists out the IEM Daily Features for a month at a time. Features have been posted on most days since February 2002. List all feature titles.
Mon Jun 02, 2025
Weekend Wildfire Smoke
02 Jun 2025 05:30 AM
The wildfire smoke from Canada was quite noticeable this past weekend aloft over Iowa with a red/orange tint to the sunlight. Some of the smoke even reached the surface dropping air quality. The featured chart looks into the impact on solar radiation. The chart displays one minute solar radiation from the ISU Soil Moisture site near Crawfordsville (SE Iowa). The smoke aloft was present both days, but the amount / thickness varied. The relatively smooth curves on both days indicates the lack of clouds, which would have made the chart much more noisy. So we find radiation flux intensity differences ranging up to 150 Watts per meter squared. The upper right legend has the day long / integrated total. The radiation total on Sunday was about 10% less than Saturday, which was also below a theoretical clear sky maximum around 32 Megajoules.
Voting: Good - 8 Bad - 0
Tags: smoke
02 Jun 2025 05:30 AM
The wildfire smoke from Canada was quite noticeable this past weekend aloft over Iowa with a red/orange tint to the sunlight. Some of the smoke even reached the surface dropping air quality. The featured chart looks into the impact on solar radiation. The chart displays one minute solar radiation from the ISU Soil Moisture site near Crawfordsville (SE Iowa). The smoke aloft was present both days, but the amount / thickness varied. The relatively smooth curves on both days indicates the lack of clouds, which would have made the chart much more noisy. So we find radiation flux intensity differences ranging up to 150 Watts per meter squared. The upper right legend has the day long / integrated total. The radiation total on Sunday was about 10% less than Saturday, which was also below a theoretical clear sky maximum around 32 Megajoules.
Voting: Good - 8 Bad - 0
Tags: smoke
Tue Jun 03, 2025
SPS Polygon Counts
03 Jun 2025 05:26 AM
The National Weather Service issues Special Weather Statements (abbreviated SPS) to typically cover storms that are slightly below severe thresholds (wind gusts below 57 MPH, hail below 1 inch diameter). Like thunderstorm warnings, these alerts can include a polygon region to delineate a sub-county area most under the specific threat. The featured chart presents an IEM accounting of the number of such SPS alerts containing a polygon (read: typically these are for convective storms) that intersects with Iowa. The values shown before 2009 were experiments and/or test usage of such polygons. Of note is the total of just 6 such alerts for May 2025. This correlates well with the daily feature last week denoting just 1 Tornado Warning for the month. The IEM offers a download portal for these polygons and also the raw issued product text.
Voting: Good - 9 Bad - 0
Generate This Chart on Website
03 Jun 2025 05:26 AM
The National Weather Service issues Special Weather Statements (abbreviated SPS) to typically cover storms that are slightly below severe thresholds (wind gusts below 57 MPH, hail below 1 inch diameter). Like thunderstorm warnings, these alerts can include a polygon region to delineate a sub-county area most under the specific threat. The featured chart presents an IEM accounting of the number of such SPS alerts containing a polygon (read: typically these are for convective storms) that intersects with Iowa. The values shown before 2009 were experiments and/or test usage of such polygons. Of note is the total of just 6 such alerts for May 2025. This correlates well with the daily feature last week denoting just 1 Tornado Warning for the month. The IEM offers a download portal for these polygons and also the raw issued product text.
Voting: Good - 9 Bad - 0
Generate This Chart on Website
Wed Jun 04, 2025
Covering the State
04 Jun 2025 05:30 AM
Outside of a few damaging thunderstorms impacting the far NW corner of the state Monday evening and the far SE corner on Tuesday, much needed rainfall blanketed the state. The featured chart attempts to quantify the efficiency of the Tuesday rainfall thanks to MRMS estimates. The chart contains two sets of bar charts. The blue bars represent the proportion of Iowa at a given precipitation departure over the past 31 days. The orange bars quantify the percentage of the total area on Tuesday that received at least a half inch of precipitation and fell over the given departure area. Of immediate notice is that practically the entire state was below average prior to Tuesday over the previous 31 days (basically May). The overall estimate is that 80% of the state got at least a half inch on Tuesday with a generally unbiased distribution of where that rain fell. Rewording, the driest areas of the state didn't necessarily miss out from this rainfall event.
Voting: Good - 11 Bad - 1
Generate This Chart on Website
04 Jun 2025 05:30 AM
Outside of a few damaging thunderstorms impacting the far NW corner of the state Monday evening and the far SE corner on Tuesday, much needed rainfall blanketed the state. The featured chart attempts to quantify the efficiency of the Tuesday rainfall thanks to MRMS estimates. The chart contains two sets of bar charts. The blue bars represent the proportion of Iowa at a given precipitation departure over the past 31 days. The orange bars quantify the percentage of the total area on Tuesday that received at least a half inch of precipitation and fell over the given departure area. Of immediate notice is that practically the entire state was below average prior to Tuesday over the previous 31 days (basically May). The overall estimate is that 80% of the state got at least a half inch on Tuesday with a generally unbiased distribution of where that rain fell. Rewording, the driest areas of the state didn't necessarily miss out from this rainfall event.
Voting: Good - 11 Bad - 1
Generate This Chart on Website
Thu Jun 05, 2025
Another Look at Precip Effectiveness
05 Jun 2025 05:30 AM
Yesterday's Daily Feature took a convoluted look at how efficient Monday's rainfall was at covering the driest areas of the state. Today's featured chart presents a different approach attempting to answer the same question of how effective Monday's rainfall was. The chart uses a RADAR based precipitation estimate product to first compute the Iowa coverage percentage of receiving at least an half inch of precipitation and what percentage of the area coincided with an area that received less than the same half inch over the previous seven days. The bottom panel is a more straight forward accounting of the daily area of the state covered by such a precipitation event and the dry area of the state under half inch over the prior seven days. The rain toward the end of May and Monday's were certainly much needed and benefited most of the state.
Voting: Good - 6 Bad - 0
Generate This Chart on Website
05 Jun 2025 05:30 AM
Yesterday's Daily Feature took a convoluted look at how efficient Monday's rainfall was at covering the driest areas of the state. Today's featured chart presents a different approach attempting to answer the same question of how effective Monday's rainfall was. The chart uses a RADAR based precipitation estimate product to first compute the Iowa coverage percentage of receiving at least an half inch of precipitation and what percentage of the area coincided with an area that received less than the same half inch over the previous seven days. The bottom panel is a more straight forward accounting of the daily area of the state covered by such a precipitation event and the dry area of the state under half inch over the prior seven days. The rain toward the end of May and Monday's were certainly much needed and benefited most of the state.
Voting: Good - 6 Bad - 0
Generate This Chart on Website
Fri Jun 06, 2025
Nearing Season Peak
06 Jun 2025 05:30 AM
A couple (here and here) of recent daily features denoted the lack of severe weather recently for Iowa. The featured chart checks in on the seasonality of NWS Severe Thunderstorm Warnings issued for Iowa. The data is partitioned by week of the year with the top panel presenting the number of years with at least one warning during the week and the bottom panel shows the overall total number of events. The tan horizontal bar attempts to estimate the meat of the season with it including about 80% of the total events. The peak of the season is somewhere between the third week of June and the first week of July. The recent lack of full sunshine and cool temperatures have certainly not helped fuel the typical summer time environment for severe weather.
Voting: Good - 16 Bad - 1
Generate This Chart on Website
06 Jun 2025 05:30 AM
A couple (here and here) of recent daily features denoted the lack of severe weather recently for Iowa. The featured chart checks in on the seasonality of NWS Severe Thunderstorm Warnings issued for Iowa. The data is partitioned by week of the year with the top panel presenting the number of years with at least one warning during the week and the bottom panel shows the overall total number of events. The tan horizontal bar attempts to estimate the meat of the season with it including about 80% of the total events. The peak of the season is somewhere between the third week of June and the first week of July. The recent lack of full sunshine and cool temperatures have certainly not helped fuel the typical summer time environment for severe weather.
Voting: Good - 16 Bad - 1
Generate This Chart on Website
Mon Jun 09, 2025
Lack of Solar Radiation
09 Jun 2025 05:30 AM
It seems like it has been a very long while since Iowans have experienced a full sun day with clear blue skies. While the sun did come out at times over this past weekend, it was mostly another couple of days with a gloomy mix of haze, clouds, and Canadian wildfire smoke. The featured chart looks into our recent stretch of gloomy weather by plotting daily solar radiation totals from the ISU Soil Moisture station just west of Ames. The black line represents an estimate of what a completely clear day would total for solar radiation. You can easily see the struggles of these past 2-3 weeks versus some of the nicer days in early May. The lack of solar radiation has been combined with seasonally cool temperatures and a bit below average precipitation, so the net effect of all this is likely a bit of stasis / limping along with development that could use warmer temperatures, more sunshine, and more precipitation! The forecast for this week has a bit of hope for all three after cool and party cloudy Monday.
Voting: Good - 13 Bad - 0
Generate This Chart on Website
09 Jun 2025 05:30 AM
It seems like it has been a very long while since Iowans have experienced a full sun day with clear blue skies. While the sun did come out at times over this past weekend, it was mostly another couple of days with a gloomy mix of haze, clouds, and Canadian wildfire smoke. The featured chart looks into our recent stretch of gloomy weather by plotting daily solar radiation totals from the ISU Soil Moisture station just west of Ames. The black line represents an estimate of what a completely clear day would total for solar radiation. You can easily see the struggles of these past 2-3 weeks versus some of the nicer days in early May. The lack of solar radiation has been combined with seasonally cool temperatures and a bit below average precipitation, so the net effect of all this is likely a bit of stasis / limping along with development that could use warmer temperatures, more sunshine, and more precipitation! The forecast for this week has a bit of hope for all three after cool and party cloudy Monday.
Voting: Good - 13 Bad - 0
Generate This Chart on Website
Tue Jun 10, 2025
SVR Count Ranks
10 Jun 2025 05:30 AM
One of the Daily Features last week presented the Severe Thunderstorm Warning climatology and showed we are nearing the half way point of the severe weather season. The first half of the season has been quite quiet around Iowa as shown by the featured map presenting Severe Thunderstorm Warning count ranks for the 1 May through 9 June period by NWS Forecast Office. A period of record back to 2002 is chosen due to IEM archive completeness and so a value of 24 would indicate the largest total for this period of years. Conversely, a value of 1 would indicate the lowest total. Iowa joins our neighbors to the west and northwest with having a well below average number of warnings for this period.
Voting: Good - 20 Bad - 0
Generate This Chart on Website
10 Jun 2025 05:30 AM
One of the Daily Features last week presented the Severe Thunderstorm Warning climatology and showed we are nearing the half way point of the severe weather season. The first half of the season has been quite quiet around Iowa as shown by the featured map presenting Severe Thunderstorm Warning count ranks for the 1 May through 9 June period by NWS Forecast Office. A period of record back to 2002 is chosen due to IEM archive completeness and so a value of 24 would indicate the largest total for this period of years. Conversely, a value of 1 would indicate the lowest total. Iowa joins our neighbors to the west and northwest with having a well below average number of warnings for this period.
Voting: Good - 20 Bad - 0
Generate This Chart on Website
Wed Jun 11, 2025
June Precipitable Water + Rainfall
11 Jun 2025 05:30 AM
Using an offline archive the IEM maintains of NWS forecast model grid point output for airport locations in Iowa, the featured chart takes a fun look comparing precipitable water (PW) and precipitation frequency. PW is a depth measure of the amount of liquid equivalent water that's in a column of atmosphere. Rewording, if all the water (in its various phases) were squeezed out of the atmosphere as liquid, how much rain would fall. So the plot compares this PW value based on the NWS NAM model with the same day calendar day rainfall total for Des Moines during the month of June. Please note that the model value is valid at 7 AM. We find a rather direct and intuitive relationship. As the atmosphere loads up with water, the frequency of observed rainfall increases! The overall climatology is around 40%, so PW values of around 1.25 inches and lower tend to have a higher frequency of dry days vs climatology. The bottom panel compares the 7 AM PW value with the same calendar day precipitation. The one-to-one line nicely shows that the PW value is often an upper bound to precipitation, but it is certainly not a hard limit and things like training thunderstorms can replenish PW during rainfall events. PW values will be on the increase this week, particularly over northern Iowa and support some significant rainfall events.
Voting: Good - 16 Bad - 1
Tags: pwater
11 Jun 2025 05:30 AM
Using an offline archive the IEM maintains of NWS forecast model grid point output for airport locations in Iowa, the featured chart takes a fun look comparing precipitable water (PW) and precipitation frequency. PW is a depth measure of the amount of liquid equivalent water that's in a column of atmosphere. Rewording, if all the water (in its various phases) were squeezed out of the atmosphere as liquid, how much rain would fall. So the plot compares this PW value based on the NWS NAM model with the same day calendar day rainfall total for Des Moines during the month of June. Please note that the model value is valid at 7 AM. We find a rather direct and intuitive relationship. As the atmosphere loads up with water, the frequency of observed rainfall increases! The overall climatology is around 40%, so PW values of around 1.25 inches and lower tend to have a higher frequency of dry days vs climatology. The bottom panel compares the 7 AM PW value with the same calendar day precipitation. The one-to-one line nicely shows that the PW value is often an upper bound to precipitation, but it is certainly not a hard limit and things like training thunderstorms can replenish PW during rainfall events. PW values will be on the increase this week, particularly over northern Iowa and support some significant rainfall events.
Voting: Good - 16 Bad - 1
Tags: pwater