Last Build Date: Mon, 20 Feb 2017 05:22:58 -0600
Very cold weather this winter has been difficult to come by as shown by the featured chart presenting the number of hours with wind chill at or below a given temperature for Des Moines. The red dots are this winter season and the blue dots are a simple average since 1973. The totals for this year are 50% of and often lower than average. The next seven days will feel more like spring than winter, so no further accumulation on this chart is expected until next weekend.
After the epic warmth expected today, you'll be hard pressed to find meaningful snow cover in the state. The featured chart displays areal coverage estimates of having at least one inch of snow on the ground this winter season. The snow cover left this morning is relegated to north central Iowa. The current forecast does not have much hope for a return of snow until at least late next week.
The Des Moines Airport was able to reach 50 degrees for the fifth time this February. The featured chart presents the number of 50+ degree days for this same 1-14 Feb period each year. The top panel shows the number of days each year with the bottom panel showing the distribution. The total of five days is around the 10% frequency, so roughly one in ten years. The largest number of such days was 15 back in 1954. Accumulating 11 more days this month to break the record is not impossible giving the current very warm forecast.
For Ames and by average temperature, February 1954 is the warmest February on record. The forecast for the rest of February 2017 looks rather warm and one may wonder if we have a chance to set the warmest February on record. The featured chart displays the combination of this year's month to date average temperature along with scenarios based on each of the previous months. None of these scenarios beat 1954, but that doesn't imply that it is impossible. Along with warm temperatures, there appears to be plenty of sunshine, which will be welcome after the gloomy January.
Very impressive warmth was observed over the middle of the country on Saturday. The featured map presents an analysis of calendar day high temperatures for February 11th. One need not travel far south of Iowa to find temperatures above 80 degrees and a bit further south to find 90s. Needless to say, these temperatures are atypical of February.
The snow that fell this week over the southern half of Iowa is not expected to last long as warm air returns in full force on Friday. The featured chart displays daily snow depth reports for Des Moines since 2000. The row representing the 2016-2017 season shows very few days with reported snow cover. Kind of interesting to compare this winter with the more extreme years of 2009-2010 and 2000-2001. The near term forecast does not hold much hope for a return of snow for the next seven days.
A snow storm finally produced snow in the state for areas other than northern Iowa. The featured map displays an analysis of snowfall reports showing an area with 4+ inches over southwestern and west central Iowa. This snow looks to be short lived as much warmer air returns to the state tomorrow with temperatures expected well above freezing. The mild weather looks to continue into next week.
The Accumulated Winter Season Severity Index (AWSSI) is some ongoing research lead by Barbara Mayes Boustead of NWS Omaha that attempts to quantify and compare the severity of the winter season. It takes into account daily temperatures, snow depth, and snowfall. The higher the index value implies a more severe winter season. The featured chart is from the AWSSI website and shows the total this year for Des Moines near the lowest accumulation to date on record for the site.
Temperatures warmed very nicely on Monday reaching levels unseen since last year for much of the state. The featured map displays the date with as warm a high temperature as seen on Monday for the primary airport weather stations. Dates valid for the year 2016 are shown in red. Temperatures will be much colder for the week until Friday when very warm air is forecasted to return.
While a somewhat obscure statistic, the range between the average daily high and low temperature for Waterloo was the smallest on record for January at just a shade under twelve degrees. The moderating impacts of having plenty of cloud cover and snow cover likely helped bringing this value in as the smallest on record. This metric isn't really a sign of having consistent temperatures over the month as the overall range was 50 degrees, but rather a general lack of having a large single day difference between high and low.
About a month ago, the same map was featured showing a significant north to south difference in the state with the number of days with at least one inch of snow depth covering the ground. Since then, the most significant snowfall only exasperated the difference with over 40 days of difference north to south over the state. The best chance of snowfall next week looks again to be confined to the northern part of the state.
The National Center for Environmental Prediction (NCEP) runs a seasonal forecast model known as the Climate Forecast System (CFS). The IEM has been archiving the morning run made each day that goes out nine months into the future. The featured chart presents each model run's forecast for average February temperature for Ames. Within the meteorological community, the CFS model has been criticized for having poor run to run consistency and the featured chart illustrates that pretty clearly. The scatter plot shows forecasts all over the board with wild fluctuations between successive model runs. One would hope to more obvious trends with successive runs providing incremental changes as the model trends warmer or cooler. So what will our February look like? Perhaps throwing a dart would be as effective :)
January is in the books now and it was a wetter than average month for nearly all of the state. The featured chart displays the distribution of precipitation totals for this month against climatology. Normal distributions are plotted by the dashed line to show a theoretical distribution. The overall average was nearly double what we'd expect for January.
A bit of sunshine was able to sneak through the clouds on Monday, which has not been common these past two weeks. The featured chart attempts to illustrate the cloudiness reports by the automated Des Moines Airport weather station. The areas in blue represent clear skies vertically up until a cloud deck is reported or the vertical limit of the sensor is reached. You can generate this chart for other sites in the country by following the 'Generate This Chart on Website' link.
For the last half of January, really cold temperatures have been difficult to come by. The featured chart displays the coldest low temperature for the 14-31 January period each year for Des Moines. This year's coldest temperature is just 18 degrees and only a few years come in with a warmer value for the same period. Considering that the average value shown is about negative 7, Des Moines has been 25 degrees warmer than that value. A general lack of snow for the period and so far this winter season for Des Moines has helped keep warmer temperatures the norm.
Based on hourly data, the featured chart displays periods lasting longer than four days in January with the temperature at or above 32 degrees. On Wednesday evening, the temperature dipped before freezing for the first time in over nine days for La Crosse, WI. This streak is over double the length in time of the previous two longest streaks. Extensive amounts of clouds during this period helped to keep temperatures warm at night and lack of snow cover helped as well!
It had been over a month since we've seen a significant snow producing winter storm in Iowa! The featured analysis of NWS COOP and Local Storm Reports shows the heaviest totals around 12 inches near the Minnesota border. The snowfall totals dropped off as one travels south in the state with Des Moines picking up an inch or so. Strong winds and below freezing temperatures are making for icy road conditions this evening.
The featured map displays cold season to date snowfall departures based on NWS Daily Climate Reports. Below normal departures are shown in red and above in blue. Much of the Midwestern US has seen below normal snowfall. It will be interesting to check back on this map in a few days after the upcoming snowstorm has passed. The heaviest totals are expected over northern Iowa.
Seeing the sunshine has been a struggle for much of this January. The featured chart considers the metric of having overcast conditions reported by the Des Moines Airport weather station at noon local time. The total for this January is well above average for the month. The forecast does not have much hope for sunshine until this upcoming weekend. On average, this month and December have the highest frequencies.
A Dense Fog Advisory is in effect for the entire state this Friday morning. The featured chart presents some frequency metrics for how often this weather alert is issued for somewhere in the state of Iowa. The top panel shows the weekly frequency of having at least one event for that week per year. The bottom panel shows the overall total number of events. The winter months are certainly the most common time of year for this product with summer having the least. Fog is easier to maintain during the winter thanks to moist air masses over top a colder ground surface which helps to keep air temperatures near water vapor saturation.