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 Feb 02, 2015

'14-'15 Winter Storm #11

It was a super snowfall for Super Bowl Sunday weekend! Snowfall totals over a foot were common from Des Moines east to Chicago. The featured snowfall analysis has most of the state over seven inches. The initial snowfall had low liquid to snowfall ratios, which made moving the snow a back-aching adventure. The tail end of the snowfall event happened at colder temperatures and combined with strong winds, made for blowing and drifting snow. Very cold air has settled into Iowa this Monday morning with even light winds creating dangerous wind chills.

Voting: Good - 23 Bad - 4


Tags:   winter1415  
Tue Feb 03, 2015

Besting the Month in One Day

The initial rainfall and subsequent liquid equivalent snowfall produced significant totals of precipitation for this time of the year. For Des Moines, the daily total on Jan 31st was greater than the total for all other days for that month. The featured chart presents the frequency of a given month having at least one half of its precipitation total fall in one day. November easily wins the competition with over half of the years meeting this criterion.

Voting: Good - 14 Bad - 4


Tags:   month  
Wed Feb 04, 2015

'14-'15 Winter Storm #12

While nowhere near the intensity of our past weekend snow producing system, a winter storm system did clip Northeastern Iowa with an inch or two of new snowfall. The featured map attempts to report only snowfall totals from that storm and not the current one that is dumping snow this morning over Southern Iowa. The map tomorrow will contain totals from the current snow producing system. For those of you that do not like the snow, much warmer weather is in the forecast with a big snow melt upcoming.

Voting: Good - 11 Bad - 5


Tags:   winter1415  
Thu Feb 05, 2015

'14-'15 Winter Storm #13

Our most recent snow producing winter storm brought 3 to 6 inches over much of southern Iowa yesterday morning. This snowfall was a much lighter (higher snow to liquid ratios) snow than what fell over this past weekend. The forecast continues to point to a warm up into the weekend that should help melt some of our recent gifts from Old Man Winter.

Voting: Good - 12 Bad - 6


Tags:   winter1415  
Fri Feb 06, 2015

Cold February Morning

Morning low temperatures on Thursday were some of the coldest so far this season with the Ames Airport hitting -22F. The featured chart presents one minute interval temperature data for a few Iowa ASOS sites. It is interesting to note the fluctuations occurring and differences between neighboring sites. The sites report in whole degree Fahrenheit, so that explains some of the jitter in the plot. On mornings like this, low micro-climate affects are strong as small pockets of cold or warmer air pass by the sensor. Once the sun takes a hold, the differences are lessened by 10 AM as the lower atmosphere mixes out small scale differences.

Voting: Good - 36 Bad - 16


Tags:   microclimate  
Mon Feb 09, 2015

Snow + Highs on Saturday

High temperatures on Saturday warmed to record levels over the High Plains, but places to the east had plenty of snow cover present which limited the amount of warming that could occur. The featured chart compares the morning snow depth reports to the afternoon high temperatures from the NWS Cooperative Network. The chart plots observations for Iowa and surrounding states. While this weekend's warm weather put a dent in the snow cover, there is still plenty of it left and more cold air expected this week to keep it around.

Voting: Good - 12 Bad - 4

Tue Feb 10, 2015

Ups and Downs of Winter

Less than three weeks remain to the Meteorological Winter Season (1 Dec - 28 Feb). The featured chart presents hourly temperatures from the Ames Airport weather sensor for this period along with the daily high and low temperature climatology. We have had stretches of warm and cold weather so far this season. The lack of snow cover for much of the season is a big reason why we had warm periods. The near term forecast has us returning to a cold stretch.

Voting: Good - 13 Bad - 7

Wed Feb 11, 2015

Mostly Normal

While light freezing rain over northern Iowa on Tuesday created some travel issues, the rest of the state enjoyed another winter day this season without much travel concern on Iowa's primary roads. The featured map displays the frequency that a given road segment was in a non-normal (non-dry) state so far this year. The percentages shown on this map are generally less than 30%.

Voting: Good - 13 Bad - 5


Tags:   roads  
Thu Feb 12, 2015

Frequency below Freezing

Temperatures will struggle today to reach the upper teens as a brisk reminder of the winter season arrives in Iowa. The featured chart looks at the hourly frequency of having a sub freezing temperature partitioned by week of the year. For mid February, having a sub freezing temperature is very common for the night time hours, but the afternoon hours are slightly less than 50%. The chart would indicate that we have at least one month of time to go before this type of weather becomes uncommon. You can generate this chart on the website for other sites and temperature thresholds of your choice.

Voting: Good - 15 Bad - 7


Tags:   temperatures  
Fri Feb 13, 2015

All Winter below 50 Degrees

The featured map displays the percentage of winter seasons that fail to reach 50 degrees for at least one day that season. There is nothing special about the number 50 for this metric. The map depicts a large contrast over our region with southern locations at or near zero percent (meaning they always see at least one day per winter over 50) and places over Minnesota approaching one hundred percent (every winter is below 50). The climate district averages are plotted, which raises the bar a bit for the threshold to be breached by a number of local weather stations and not just one. It is interesting to note that the gradient is not a flat north to south one, but tilts as you approach the high plains. The proximity to the mountains helps those locations warm quickly as down slope wind events drive rapid warm ups.

Voting: Good - 40 Bad - 21


Tags:   winter  
Mon Feb 16, 2015

Downhill on Valentines Day

The featured table shows the hourly temperature reports from the Des Moines Airport for Valentines Day. The temperature fell the entire day after starting out at 36 degrees at midnight and dropped to 6 by the end of the day. The chart displays the most recent Valentines Day with as cold an hourly temperature. For hours after 10 AM, you have to go back to 2007 for temperature as cold as this year.

Voting: Good - 20 Bad - 9


Tags:   valentines  
Tue Feb 17, 2015

Downward Days

On Saturday, the hourly temperature at the Des Moines Airport was unchanged or got colder with each successive hour. This is a somewhat rare occurrence with the last such day like it back on 27 November 2011. The featured map provides an analysis of station frequency of having such an occurrence since 1973. Setting aside some local climate effects, the map shows the general pattern of having the highest counts over northern US. For this type of event to occur, the cold air advection must be very robust to overwhelm any bit of warming that may happen during the day with sunshine present.

Voting: Good - 16 Bad - 5


Tags:   cold  
Wed Feb 18, 2015

Wind Chill Alerts

The NWS has a Wind Chill Advisory issued for today as another round of very cold air arrives in the state today. The featured chart displays computed wind chill values for Ames along with periods with either a wind chill advisory or wind chill warning active. These alerts are not always issued when temperatures get very cold along with very light winds as what happened a few weeks back. High temperatures today will struggle with some locations not exceeding the single digits.

Voting: Good - 16 Bad - 8


Tags:   windchill  
Thu Feb 19, 2015

Cold above us as well

Even with plenty of sunshine on Wednesday, temperatures struggled well below freezing. There is currently plenty of cold air at the surface and above our heads as shown by the featured chart of 850 hPa temperatures for the Omaha sounding site. We've had two periods of near record warmth at this level followed by our current period at near record cold. This level is just a few thousand feet above our heads and represents air that is potentially mixed down during the say as the sun mixes the lower atmosphere.

Voting: Good - 18 Bad - 7


Tags:   sounding  
Fri Feb 20, 2015

East and West CONUS

The nation's recent weather pattern has been persistent with warm air in the western US and cold air in the eastern US. The featured map displays the current streak of days above or below climatology for daily high temperature. Some locations in the far east and west are at some rather gaudy numbers at the moment. Iowa is currently siding with the eastern US with recent temperatures well below average. The near term forecast looks to persist this current pattern, so these totals should continue to grow!

Voting: Good - 39 Bad - 24


Tags:   nwscli  
Mon Feb 23, 2015

Winter Mins

The featured map presents the minimum temperature reports from airport weather stations in the state so far this winter. This analysis suggests the entire state has seen sub zero temperatures, but local micro climates make a big difference with how cold a location can get. For example, Des Moines Airport has only dropped to -10 while Ankeny has reached -18 and Ames -22.

Voting: Good - 12 Bad - 8

Tue Feb 24, 2015

Daily Snow Depth

The featured chart displays daily snow depth reports for the Ames COOP site since 1964. Even with below freezing temperatures, our current snow pack has been slowly disappearing. Sun shine and dry air are able to eat away at the snow even with air temperatures below freezing. The chart nicely shows the winters with the most persistent snow cover, like 2000-2011 and 1977-1979. You can generate this chart online for other sites in the region.

Voting: Good - 16 Bad - 10


Tags:   snowdepth  
Wed Feb 25, 2015

Spring Starts Soon?

With winter storm warnings in effect for today and another round of very cold air set to arrive after the snowfall, it is difficult to imagine that spring time is almost here. The featured map looks at the end date of the coldest 91 day period based on daily climatology from NCDC. If you divide the year up into 4 equal length seasons (~91 days) and then compute the coldest stretch of 91 days, you could consider this to be winter. So once this stretch ends, you are then in springtime! This analysis shows that Iowa is only a few days from starting spring, but this year will be a bit different as a cold February and warm December will cause the coldest 91 day period this year to shift well into March.

Voting: Good - 18 Bad - 5


Tags:   spring  
Thu Feb 26, 2015

'14-'15 Winter Storm #14

Our most recent snow producing winter storm brought 4-7 inches over much of eastern Iowa on Wednesday. Totals dropped off significantly to the west with southwestern Iowa missing out completely. The entire state is experiencing the cold air arriving behind this storm system and below freezing temperatures are expected into the first week of March.

Voting: Good - 11 Bad - 4


Tags:   winter1415  
Fri Feb 27, 2015

Records by Year

A daily record low temperature for Waterloo has been set this morning, so it is good timing to look at the yearly frequency of setting a new high and low record temperature. The featured chart presents this metric by computing the number of new records set each year from the beginning of the period of record. The black line represents a sort of theoretical expected frequency based on the number of years that have passed. During the beginning of the record, there are much fewer years of history so it is a bit 'easier' to set records. Years that exceed this expectation are colored differently. For recent years, the warm weather of 2012 certainly stands out as an anomaly.

Voting: Good - 32 Bad - 21


Tags:   records