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.

Features for May 2020

Fri May 01, 2020
Needed Dry April
01 May 2020 05:02 AM
The featured chart presents IEM estimated areal averaged precipitation for Iowa during the month of April. After a wet fall and elevated soil moisture levels, we needed a dry April to allow for spring planting. The precipitation total shown is very much on the dry side of average and one of the lowest values seen since 1980. Combined with recently warm air temperatures and we've had near ideal conditions to allow for rapid spring planting progress. The only concern at this point is if colder weather shows up in May, which we generally are forecast to miss at the moment with the coldest air staying off to our east.
Voting: Good - 13 Bad - 2

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Mon May 04, 2020
Lovely 70s
04 May 2020 05:14 AM
Outside of some limited rain showers, the weather this past weekend was spectacular with plenty of time spent with temperatures in the 70s. The featured chart presents the frequency of having an early afternoon temperature in the 70s by month based on period of record data from the Ames Airport. The brown bars represent the monthly frequency in the 70s with the red dots showing the frequency above the 70s and blue below. For May, it is more common to be below the 70s than above, which will be the case for much of this week as temperatures cool off.
Voting: Good - 10 Bad - 0

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Tue May 05, 2020
Doing well for 60s
05 May 2020 04:13 AM
High temperatures cooled off on Monday back into the lower 60s, which is a bit below average for the first week of May. So far this year, Des Moines has been doing well for having days in the 60s as shown by the featured chart. The chart counts the number of days this year, last year, and on average that the high temperature is within the range shown for the year to date period. This year has provided about five more days than average in the 60s. The forecast for the rest of the week has more days in the 50s even than 60s.
Voting: Good - 14 Bad - 0

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Wed May 06, 2020
Severe TStorm Warning Season
06 May 2020 05:20 AM
As temperatures struggle this week and the weather feels more like mid spring than early summer, the featured chart denotes that May is clearly within the severe weather season for the state. The featured chart presents the weekly frequency of Severe Thunderstorm Warnings issued by NWS Des Moines. The peak of the season is during June with May coming in second for overall events. These severe events are often forced by strong surface heating that helps build instability in the atmosphere helping to feed thunderstorms. The air mass near the surface for this week is rather cool, so any heating will likely only drive modest showers.
Voting: Good - 10 Bad - 0

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Thu May 07, 2020
Cold Saturday Morning
07 May 2020 04:38 AM
The featured chart is of forecast air temperatures for Waterloo from various sources provided by the venerable Bufkit Warehouse website. The plot shows the continued downward slide in temperatures to finish out this week with lows reaching near 30 degrees on Saturday morning. Getting freezing temperatures for early May is not exceptional, but any early planted and tender plants would need to be covered and so the NWS has a Freeze Watch issued for the period.
Voting: Good - 9 Bad - 0

Tags:   bufkit  
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Fri May 08, 2020
Coldest May Lows
08 May 2020 04:30 AM
The featured chart presents the top 10 coldest May daily low temperatures for Ames. The forecast low for tonight into Saturday morning is just 32 degrees, which is not too far from as cold as it can get this time of year. For temperatures 32 and below, one has to go back all the way to 1997 (May 13) to find as cold a temperature for May 8th or later. Please cover any sensitive plants you have!
Voting: Good - 12 Bad - 0

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Sat May 09, 2020
Historic May Cold
09 May 2020 08:17 AM
Morning low temperatures on 9 May 2020 were quite cold for early May with frost reported over much of the state. The featured table presents some preliminary low temperature reports from the main airport weather stations in the state along with some unofficial historical context for how today's low ranks all-time for May and for dates after 9 May. Waterloo and Ottumwa appear to have had their coldest low temperatures this late into the spring season on record. It will be interesting to see how much damage these below freezing temperatures did.
Voting: Good - 18 Bad - 0

Tags:   may  
Tue May 12, 2020
May Below Freezing Hours
12 May 2020 05:27 AM
Morning low temperatures are once again chilly with near or slightly below freezing temperatures expected over northern Iowa. The featured map presents the accumulated number of hours spent below freezing based on hourly interval grid analysis data from the NWS. The huge caveat with this map is that the input values are hourly snapshots of temperature and not true time integrated values over a finer temporal scale. The dips and rises in morning temperature tend to be rapid and not always well represented by hourly data (more on this with tomorrow's feature). The map nicely shows the topographic features of the region with the Nishnabotna Valley influence clearly visible over southwestern Iowa.
Voting: Good - 15 Bad - 1
Wed May 13, 2020
Sub-Hourly Variability
13 May 2020 05:40 AM
The featured chart is an illustration of the interesting sub-hourly temperature variability that exists. The chart compares minute observations vs hourly temperature samples from the Cedar Rapids ISU Soil Moisture Network station back on 9 May (significant freeze event). The station reports minute averaged temperature values based on 15 second interval samples. The top panel shows the minute by minute values along with hourly sampled values from the same source data set, thus the two lines overlap at the top of each hour. The bottom panel shows the difference between the two lines with the 60 minute sample data linearly interpolated back to 1 minute interval. The difference between the two lines is rather remarkable with the most fascinating activity happening between midnight and 2 AM with the differences above 3 degrees each hour. An simple explanation is elusive at the moment, but likely due to micro-climate air flows and/or fun things happening as the air temperature dipped below freezing and various heat fluxes kicked in with the freezing of water.
Voting: Good - 9 Bad - 1

Tags:   minute  
Thu May 14, 2020
Iowa in the Lead
14 May 2020 04:37 AM
For Midwestern states, Iowa is in the lead for corn crop planting progress according to the weekly crop progress update made by the USDA on Monday. The featured map presents the statewide estimates along with a departure from the previous ten years. Outside of some recent chilly temperatures, this spring has been near ideal for planting in Iowa. Conditions have been wetter to our southeast, which has slowed progress there. The forecast has our weather turning back to more summer time conditions with chances of needed (imagine saying that a few months back) rain and warmer temperatures.
Voting: Good - 15 Bad - 1

Tags:   nass   cron  
Fri May 15, 2020
3 inch Hail
15 May 2020 03:29 AM
A powerful storm just south of Des Moines dumped large hail up to three inches in diameter Thursday afternoon. The featured map presents a preview of an upcoming hail size estimate product produced by the IEM based on NOAA MRMS MESH along with available NWS Local Storm Reports centered over southern Iowa. The MESH product uses RADAR data and algorithms to produce estimates of maximum hail size. The three inch report aligns well with the estimated maximum in the product. The data presentation shown is not yet available on the website for generation, stay tuned!
Voting: Good - 15 Bad - 1

Tags:   mesh   hail  
Mon May 18, 2020
Ottumwa Tied May Record
18 May 2020 04:11 AM
The big hail producing storm last Thursday also dumped significant amounts of rainfall. Ottumwa received 4.43 inches and tied their all-time May record for daily precipitation. The featured chart presents the maximum daily precipitation by month. Having such extreme precipitation totals are a function of how much water the atmosphere can hold. Thus the reason such large values are confined to the warm half of the year as cold air has less capacity to hold water vapor.
Voting: Good - 8 Bad - 0

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Tue May 19, 2020
Recent Cloudiness
19 May 2020 05:00 AM
The featured chart presents categorical flight condition values based on Des Moines Airport weather station data this month. The flight category combines visibility and cloud ceiling values to guide aviation operations. The green values are at least five miles of visibility and three thousand feet ceilings, which have been rare for the past few days. The forecast for the rest of this week looks to continue the recent trend of cloudiness with chances of rain as well. At least temperatures will be warmer with 80s expected by the weekend.
Voting: Good - 9 Bad - 0

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Wed May 20, 2020
Cool May Start
20 May 2020 05:32 AM
Having above average high temperatures so far this May has been a bit of a struggle. The aggregate departure for daily high temperature this May is shown by the featured map. The coldest departures are indicated over eastern Iowa with the coldest plotted value near eight degrees below average. Such chilly temperatures are important to the agricultural crops, which mostly got planted during excellent weather in April, but have now had slow progress due to the lack of heat. The forecast continues to have optimism that warmer temperatures, above average, will arrive for the weekend.
Voting: Good - 11 Bad - 0

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Thu May 21, 2020
Decorah Wins
21 May 2020 02:22 AM
Typically being located in the far northeastern corner of Iowa means you experience some of the cooler temperatures within the state. Wednesday was an exception to that generality with Decorah (site id: DEH) reporting the warmest high temperature near 72 degrees. The reason why Decorah was the warmest was the location actually saw significant sunshine whereas the most of the rest of the state was cloudy. The featured chart compares an IEM produced solar radiation estimate based on HRRR model data against the reported high temperature for airport weather stations in the state. Selected sites are labeled by their station identifier. The relationship between the two variables is clear with increasing sunshine leading to warmer temperatures.
Voting: Good - 10 Bad - 0

Tags:   solar   radiation  
Fri May 22, 2020
Done with Gloom Soon?
22 May 2020 04:57 AM
The recent lack of sunshine and associated chilly temperatures is starting to get old. This gloomy weather has included plenty of time with overcast skies and low cloud ceilings. The featured chart presents a histogram of overcast skies and at what level those reports occur at using period of record observations from the Ames Airport. There are caveats galore with this plot including important quirks with how the ceiling readings are reported by automated sensors. The y-axis scale is also logarithmic to better detail the low level conditions. The point of the plot is the frequency of low clouds and generally overcast conditions starts to decrease by the end of May. Warmer soil temperatures, increasing solar inputs and warming lower atmosphere all help to mix the boundary layer and relegate clouds to higher levels. The forecast has at least warmer temperatures, but still appears to keep gloomy conditions around for a few more days at least!
Voting: Good - 15 Bad - 1

Tags:   clouds  
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Features for May 2020