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 Feb 2022

Tue Feb 01, 2022
US Population under WaWA
01 Feb 2022 05:30 AM
The NWS issues Watch, Warnings, and Advisories (WaWA) for the protection of life and property. The featured chart attempts to summarize the currently active events by summing the number of people currently under the given alert type. This is computed by intersecting the active alert geometries with a 30 arc second grid population estimate from 2020. Presently, winter weather headlines stretch from Texas to New England as a powerful winter storm looks to paint a stripe of heavy snowfall and significant ice accumulations. At this point, most of Iowa will miss out on this storm with the significant impacts passing just to our south, but far southeastern Iowa will be clipped by the storm. You can generate this summary chart for any valid timestamp you want back to October 2005, which is when more programmatic WaWA alerts began to be issued by the NWS.
Voting: Good - 13 Bad - 0

Tags:   population  
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Wed Feb 02, 2022
Groundhog Day Forecast
02 Feb 2022 05:34 AM
It is a cruel irony that today is Groundhog Day and Saturday is Weatherperson (Meteorologists) Day as the former is the bane of the existence of the latter. For those that believe in a groundhog's forecast, the weather lore states that if an emerging groundhog sees its shadow, it will retreat back into its hole and six more weeks of winter will commence. The featured table looks into this forecast based on a theoretical groundhog here in Des Moines with the shadow metric estimated by Des Moines airport sky coverage at 7 AM. The two data columns present that year's six week total for snowfall and average temperature and if those values were a snowier/colder departure than average (more winter) or a less snowy/warmer departure (more spring). The last column grades the forecast. Of course, one may argue if these metrics are an appropriate means to grade the forecast, but we are attempting to discuss a forecast made by a groundhog here, so about anything goes!
Voting: Good - 15 Bad - 1

Tags:   groundhog   folklore  
Thu Feb 03, 2022
'21-'22 Winter Storm #7
03 Feb 2022 08:41 AM
The first wave of two powerful winter storms just clipped the southeastern corner of Iowa on Tuesday into Wednesday. The featured map analysis shows the tight gradient with the largest report of five inches found in the far corner of the state. The second system will pass further to our south and east and likely completely miss Iowa with any snowfall. What is not missing though is cold temperatures and dangerous wind chills again. This stream of very cold air is helping to produce the snow and ice accumulations to our south as cold temperatures are needed to sustain freezing rain events.
Voting: Good - 9 Bad - 0

Tags:   winter2122  
Fri Feb 04, 2022
January PRISM Departures
04 Feb 2022 05:35 AM
Tracking precipitation departures during the cold season can be problematic as climatological accumulations this time of year are minimal, there's no plant activity, and precipitation estimates struggle when it snows. The updated US drought monitor released yesterday did so some expansion of the "D0" (Abnormally Dry) classification over eastern Iowa. The featured map presents PRISM computed precipitation departures for January 2022. Much of the upper Midwest is shown below average with only a few pockets slightly above. Drought concerns from last year continue to linger into this year, but this is generally not the time of year we can make up deficits. The months of March and April will bear watching to see if more meaningful rainfalls can come!
Voting: Good - 19 Bad - 0

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Mon Feb 07, 2022
Time near High
07 Feb 2022 05:33 AM
While temperatures did warm nicely on Sunday, the time at those very nice temperatures was fleeting with a cold front sweeping the state during mid day. The time spent each day near the high temperature is the subject of today's featured chart. Using one minute interval observations from the Des Moines airport since 2000, the chart prevents violin plots by month showing the amount of time spent within three degrees of a given day's high temperature. Violin plots are similar to box and whisker plots, but also attempt to provide more details into the shape of the distribution with fatter sections representing more population density. The black bars within the violins show the inter-quartile range with the white dot representing the mean value. The chart nicely shows the difference between the cool and warm half of the year with ranges during the winter season much larger than during the summer. The reason why is the effectiveness of solar heating, which in the summer nearly always pushes temperatures upward during the day and thus limits the amount of time spent near the high temperature. The winter season is more dominated by air masses and cloudy days can make for limited temperature range during the day, thus increasing the time spent near the high. An additional subtle feature shown is the lack of values over 20 hours during June and July. Again, the reason is the sun as it is extremely difficult to have days during peak solar heating without a diurnal temperature response.
Voting: Good - 15 Bad - 0
Tue Feb 08, 2022

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Imagery courtesy of NASA Earthdata
Depressing Gradient
08 Feb 2022 05:35 AM
Temperatures on Monday were depressing for those of us stuck on the snow covered side of the state. The featured map presents the combination of NOAA20 VIIRS satellite true color imagery along with high temperatures from the airport weather stations. While some of the whiteness shown on the map is from clouds, the relationship between snow cover and high temperature is readily apparent. Amazing to see the east/west contrast between Sioux City at 60 degrees and Dubuque at 20. The good news is that winds are forecast to pick up on Tuesday, which will help push and mix warmer air into the snow covered region of the state and hopefully start a more substantial melt of our icy landscape.
Voting: Good - 14 Bad - 0
Wed Feb 09, 2022
85% of month in one day
09 Feb 2022 05:34 AM
From the somewhat obscure stats department, the featured chart presents the frequency of one day within a given month providing at least 85% of that month's total precipitation. Such an occurrence happened back on January 14th, with 1.03 inches of precipitation reported for Des Moines and the monthly total only reaching 1.21 inches making for 85.1% of the monthly total falling on that one day. The labels above the bar include the year of last occurrence and November 2021 is shown reaching the criterion with 1.35 inches falling on the 10th and only 1.54 total for the month! It is sort of interesting to see the large difference between November and December, which may be due to November being a dry month to begin with, but still subject to the occasional thunderstorm or single significant snow storm. Anyway, these events are very infrequent during the summer as heavy rainfall events like to beget other heavy rainfall events (positive feedback) and monthly totals are much higher on average making a single day total less likely to reach it.
Voting: Good - 11 Bad - 0

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Thu Feb 10, 2022
Red Flag Warnings
10 Feb 2022 05:26 AM
Earlier this week, the NWS had a Red Flag (Fire Weather) Warning active for a few counties in far western Iowa. These warnings mean that ignited fires could uncontrollably spread due to low humidity, combustible ground surface, and strong winds. As the featured chart shows, it is an early start to the fire weather season. The chart depicts the period each year between the first and last such warning for somewhere in Iowa. The average start date is still some six weeks from now. For areas of the state without any snow cover, the recent dryness, windy and warmer conditions have increased the fire spreading threat. The near term forecast continues to be very dry and perhaps some of these warnings will again be necessary next week with expected warmer and windy conditions.
Voting: Good - 13 Bad - 1

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Fri Feb 11, 2022
Mid-February Rain
11 Feb 2022 05:34 AM
The precipitation that fell from the sky Thursday evening mostly came in the form of rain, making for the first rain event for the state in quite some time. Temperatures fortunately warmed as well to limit significant impacts from icing and kept the accumulating snow that did fall, to a minimum. The featured chart presents a climatology based on hourly Ames airport weather station data showing the temperature at which measurable precipitation was reported. A weekly weighted average line is plotted as well along with a 32 degree baseline temperature. About the third week of February is when we start to see above freezing precipitation events increase in frequency. Of course, there is still plenty of time for big snowfalls, but we are trending in the right direction now for those sick of full scale winter!
Voting: Good - 17 Bad - 2

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Mon Feb 14, 2022
Just One Big Event
14 Feb 2022 05:32 AM
The featured chart presents year to date accumulated precipitation. The total for this year is almost completely thanks to the one large snowfall event back in January. It has been rather dry otherwise and after a year plagued by drought last year, we are not off to a promising start this year. It is early yet and with frozen soils, any rainfall events are likely mostly lost to runoff anyway. We do, at least, have a storm forecast for mid week, but the amount of received precipitation remains in question.
Voting: Good - 14 Bad - 0

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Tue Feb 15, 2022
CoCoRaHS Observers by County
15 Feb 2022 05:35 AM
The Community Collaborative Rain Hail and Snow (CoCoRaHS) project has one of the wildest acronyms you will see. The national project aims to promote citizen science by supporting the daily collection of precipitation reports. The featured map presents the number of CoCoRaHS reporters by county who have made at least one daily report over the past year. It would certainly be nice to have at least one reporter per county in the state, but everyone is encouraged to consider joining the project. You can find more details on the project's website.
Voting: Good - 17 Bad - 1

Tags:   cocorahs  
Wed Feb 16, 2022
Just Six Snow Days
16 Feb 2022 05:30 AM
The lack of snow producing storm events this winter season to date has been noticeable. The featured chart presents the number of days per season with measurable snowfall between 1 September and 15 February. The total shown for Des Moines this season is just six days and only two days more than the all-time low of just four days during the 1953-1954 season. The simple long term average is 17 days, so we are well below average this year! The side tables show the top ten largest and smallest totals with just two years ago showing up in the top ten. Since snowfall storm events can cross arbitrary day boundaries, you should not construe the day totals as equating snow storms. Additionally, while the number of days is well below average, the actual snow accumulation is not too far from average as one of the events was the massive dump during mid January.
Voting: Good - 14 Bad - 1

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Thu Feb 17, 2022
February Percentiles
17 Feb 2022 05:26 AM
This February has been a roller coaster for temperature as persistent flow aloft from the northwest has kept Iowa within the battle ground of air masses. The featured chart presents some air temperature metrics for Ames during February. The top panel shows temperature percentiles by hour based on period of record data. The bottom panels show a time series of percentile values based on per hour populations for the month. The side panel at the bottom shows a histogram of hourly reports by decile. The roller coaster is certainly obvious by the lower panel and the histogram shows that we have spent more time at the extremes than in the middle this month so far. The forecast for the next week continues this wild ride with some days having high temperatures well below freezing and others well above.
Voting: Good - 7 Bad - 0

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Fri Feb 18, 2022
'21-'22 Winter Storm #8
18 Feb 2022 08:07 AM
Another significant winter storm again passed off to our south and east and only clipping extreme southeastern Iowa with upwards of five inches of snow reported at Keokuk. The featured analysis is likely too generous with the analyzed snow to the northwest of that five inch report. Will likely remake this map later today once more reports in that region are received. The weather continues to be quite variable with a rapid warm up forecast for today along with some rain/snow chances this evening, then crashing temperatures again, then another rapid warm up, then another crash in temperatures along with a decent chance of snow next week. Precipitation producing storms are certainly welcome as we generally need moisture.
Voting: Good - 6 Bad - 1

Tags:   winter2021  
Sat Feb 19, 2022
'21-'22 Winter Storm #9
19 Feb 2022 07:28 AM
While a quick hitting system Friday evening did not bring that much snow, it was certainly very impactful and warrants an IEM storm accounting map. This system prompted the National Weather Service to issue a number of Snow Squall Warnings, which is a special product to cover temporary white-out conditions due to falling snow and strong winds. For a number of NWS Offices, this was their first issuance of such a warning (this warning type is relatively young compared with others). Anyway, actual snowfall totals were an inch or less over far eastern Iowa. The Snow Squall Warning polygons are shown in the purple color and conditions warranting these warnings were even worse over Wisconsin and Illinois last evening.
Voting: Good - 13 Bad - 0

Tags:   winter2122  
Mon Feb 21, 2022
Bouncing February Highs
21 Feb 2022 05:27 AM
The weather cliche about if not liking the weather, wait five minutes, has certainly applied this February as day to day temperatures continue to bounce wildly around. Case in point, this past weekend with chilly temperatures on Saturday giving way to spectacular warmth on Sunday and how a dive back toward winter on Monday. Of course, the IEM Daily Feature is here to put numbers behind this perception. The chart displays the average absolute value difference between sequential daily high temperatures for Ames during February. While this February does have a week to go yet, the value shown thus far is the largest on record. The 12.5 value for this February means that, on average, the next day high temperature has averaged a difference of 12.5 from the current day high. After a high in the lower 60s on Sunday, Monday is expected about 15 degrees cooler and then Tuesday another 20 degrees cooler, both of which would increase the average change value for the month!
Voting: Good - 17 Bad - 0

Tags:   feb22  
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Tue Feb 22, 2022
Icy Twosday
22 Feb 2022 05:31 AM
The day that the number two is wild (2/22/2022) is starting off icy with light freezing rain common over the state. The featured map presents Iowa winter road conditions as of 5 AM this morning with icy conditions shown in pink. More freezing rain and snow is forecast for today, but the worst of the winter weather will be off to our north in Minnesota and Wisconsin. Temperatures will turn colder and remain cold for the much of the remainder of the week. So much for the 60s some Iowans enjoyed on Sunday and Monday!
Voting: Good - 12 Bad - 3

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Wed Feb 23, 2022
'21-'22 Winter Storm #10
23 Feb 2022 08:27 AM
While the winter storms have come at a frantic pace as of late, the most significant impacts from each time to skirt just outside of the state. While the most recent storm did not produce much in the way of snowfall for Iowa with totals generally an inch or less over northern Iowa, there was travel impacting accumulations of freezing rain and sleet over much of the state on Tuesday. The good news was that it fell during the day, so the meager sunshine and road treatment was able to clear it away. Another big winter storm event is in progress today, but will miss us off to the south again. We are left though with bitter cold temperatures again as our recent taste of spring on Sunday and Monday seems like a dream at this point.
Voting: Good - 11 Bad - 2

Tags:   winter2122  
Thu Feb 24, 2022
Highs below 10
24 Feb 2022 05:34 AM
Sioux City was only able to reach nine degrees for a high temperature on Wednesday. While one would hope we are close enough to spring to prevent such cold temperatures, we are still in February and such cold is still well within climatology for this time of year. The featured chart presents monthly percentiles and return intervals for having a daily high below ten degrees for Sioux City. For February, the return interval is about five days every three years. The frequency does decrease significantly going into March, so hopefully we can soon get past this very cold weather and start some semblance of sustained spring weather!
Voting: Good - 8 Bad - 4

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Fri Feb 25, 2022
'21-'22 Winter Storm #11
25 Feb 2022 08:11 AM
Not all snowfalls are created equal, the differentiation if often how much liquid water the given snowfall melts down to. This is called the snow to liquid ratio (SLR) and is often assumed to be 10 to 1, meaning 10 inches of snowfall would melt to 1 inch of liquid water. The actual long term average of SLR in Iowa is likely closer to 13 or 14 to 1. Anyway, the most recent winter storm brought very fluffy snow to the state thanks to frigid cold near surface temperatures and an atmospheric temperature/moisture profile that supported large snowflake production. SLR values from this event are in the 30 to 50 range, which shows you how much variability there is with SLR. The featured map presents snowfall totals with a stripe in the 3 to 5 inch range from Des Moines to Dubuque.
Voting: Good - 17 Bad - 2

Tags:   winter2122  
Mon Feb 28, 2022
Winter to Date
28 Feb 2022 05:34 AM
No matter how you wish to classify the winter season, getting to the end of February is good news for those of you sick of the season. The weather over these past three months has been rather eventful, but we have mostly avoided extremely cold conditions here in central Iowa. The featured chart presents the number of hours for Des Moines at or below a given wind chill value. This season's total is plotted along with a simple climatology. It is interesting that for thresholds above about -15 degrees, this winter has seen more hours at that threshold than on average. For thresholds below -15, we are well below average. The forecast for this week looks amazing with no chance of adding hours to this plot with highs well above freezing and lows not far from there.
Voting: Good - 14 Bad - 0

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Features for Feb 2022