Past IEM Features tagged: snowcover

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Snow Cover About Gone

16 Feb 2017 05:35 AM
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.

Voting:
Good: 9
Bad: 1

Tags:   snowcover  

Few Days of Snow Cover

10 Feb 2017 05:37 AM
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.

Voting:
Good: 20
Bad: 0

Tags:   snowcover  

Snow Cover Impact

07 Dec 2015 05:34 AM
It stands to reason that having snow cover makes a big difference in what air temperatures can be expected. The current stretch of mild weather is thanks to a mostly snowless Iowa. The featured chart displays the monthly average daily high and low temperatures partitioned by the presence of snowcover reported on the same day as the temperatures. There are some caveats to this plot given the timing of temperature and snowcover reports, but the impact is clear. While our current high temperatures are above average, they are not too far from what we'd expect on days without snow cover.

Voting:
Good: 14
Bad: 4
Abstain: 3

Tags:   snowcover  


Obvious Relationship

11 Mar 2014 05:37 AM
After a wonderful Sunday, Monday was able to top it with temperatures soaring to levels not seen since last year. Sioux City was able to tie a record high temperature of 74 degrees. Not all of the state was able to get that warm and the sole reason was the deep snowpack that still exists over much of northeastern Iowa. The featured chart shows the obvious relationship between morning snow cover and the afternoon high temperature over Iowa for Monday. A forecasting rule of thumb states that the high temperature can not exceed 43 degrees when there is at least four inches of snow depth present in the morning, but this rule does not hold when significant warm air advection is happening. Warm air advection is the process of moving warmer air into areas with colder air. This warm air from the south helps to push temperatures even warmer.

Voting:
Good: 24
Bad: 11
Abstain: 6

Tags:   snowcover  


Snow Cover and Highs

19 Feb 2014 05:41 AM
Tuesday was a welcome relief from winter with nearly the entire state reaching 40+ degrees for a high temperature. The feature chart presents the afternoon high temperature vs the reported snow cover depth yesterday morning. This comparison is made between a grid analysis of both observed variables. The relationship is clear with areas with the least amount of snow having the warmest temperatures. The snow free areas in western Iowa were able to reach the 60s! Our winter relief will not last long as Iowa gears up for an expected blizzard on Thursday.

Voting:
Good: 25
Bad: 5
Abstain: 3

Tags:   snowcover  


Colder with snow cover

11 Dec 2013 05:45 AM
The featured chart shows the daily averaged difference in temperature between days with snow cover and with out. The temperature difference is for the next seven days after the analyzed date. The chart is attempting to show the temperature effect when there is snow cover versus not. The approximate average of the chart is negative five degrees, meaning that the presence of snow cover on a given winter day produces, on average, a next seven day period that is five degrees cooler than the same period when the first day is snow free. The results are intuitive as snow cover helps temperatures cool more rapidly at night and prevents incoming sunshine during the day from heating the ground. Our weather is going to remain very cold with our current snow cover that is being added to this morning with our most recent round of winter weather.

Voting:
Good: 31
Bad: 6
Abstain: 8

Tags:   snowcover  


White till Christmas?

10 Dec 2013 05:45 AM
With the ground covered in snow and freezing temperatures in the forecast, could our current snow cover make it to Christmas Day? The featured chart presents the duration of snow cover when it was present on 9 December for Des Moines. Christmas is shown at 50%, meaning that half of the years with snow cover on the 9th had that snow stick around until Christmas. 25% of the the years had the snow stick around until the first of February even! Winter is in firm control of our weather with even colder weather expected tomorrow.

Voting:
Good: 23
Bad: 2

Tags:   snowcover  


caveats galore with archived snow cover data quality and timing

Snow Cover and Cold Lows

27 Nov 2012 05:39 AM
Temperatures dropped quickly Monday evening thanks to clear skies and calm conditions. Our saving grace was ground temperatures which are still warm for this time of the year and the lack of snow cover, which prevented temperatures from dropping even further. Snow cover is a game changer when it comes to the surface energy balance during the day and night time. It acts to mostly seperate the exchange of energy from the sun to the soil and back to the air. The featured chart presents the frequency of having snow cover at a given daily low temperature (blue line) and the overall frequency of that temperature (red line). The main point is to show that the coldest temperatures are increasing associated with the presence of snow cover. For example, a low temperature of zero degrees also had snow cover present 90% of the time. The chart also had an interesting (but unexplained here) aspect of having the lines cross at the 50% probabilities for both y-axes around 18 degrees. It is difficult for near surface soil temperatures to get cold enough to support very cold air temperatures, so snow cover is increasing necessary for the coldest temperatures.

Voting:
Good: 40
Bad: 7

Tags:   lows   snowcover  


Snow and no snow

16 Jan 2012 05:48 AM
The high temperature you experienced on Sunday in Iowa was very dependent on the amount of snow you received from our storm last week. Warm air surged into the state, but thanks to snow cover over eastern Iowa temperatures were much cooler than the mid 50s over western Iowa. This contrast is nicely shown by overlaying high temperatures on Sunday to visible imagery showing areas with and without snow. The forecast for this week looks to be active with another warm up expected next weekend.

Voting:
Good: 25
Bad: 5

Tags:   snowcover   satellite  


White Christmas Influence

23 Dec 2011 05:58 AM
The featured chart presents the observed daily frequency of snowcover partitioned by if there was snow cover on Christmas and the overall average is shown. The highlighted area shows the period were these three lines show visual differences, which is a way to show the memory of having a white or brown Christmas. In other words, by mid February the frequency of having snow cover does not relate to if we had snow cover on Christmas. Back to the matter at hand of our snow state for this Christmas, well it will be brown with very warm temperatures in the 40s!

Voting:
Good: 25
Bad: 14

Tags:   snowcover   christmas  


Warmer March in store?

15 Feb 2011 05:55 AM
The past few days of much warmer weather has helped to eliminate much of the snow that has stuck around for most of winter. The featured chart looks at the relationship between having snow on the ground of a given day in February and then the average temperature that following March. The implication is clear, getting rid of the snow now leads to a few more degrees warmer weather in March. The chart also shows that the coldest, on average, March temperatures are when there is snow at the end of February and the warmest are when there is no snow at the beginning of the month.

Voting:
Good: 13
Bad: 6

Tags:   snowcover   feb   mar  


Snow brings the cold

20 Jan 2011 05:50 AM
The average temperature so far this month is about 5 degrees below normal for Ames with each day having snow cover so far. The featured chart presents the relationship between observed average temperature departure and number of days with snow cover for January. While the linear fit is not perfect, the relationship is fairly clear. The preliminary value so far for 2011 is shown by the plus symbol. The chart shows the coldest five months all having snow cover for 30 or 31 days.

Voting:
Good: 16
Bad: 6

Tags:   snowcover   jan  


The hindrance of snow

03 Jan 2011 05:47 AM
Temperatures soared last Thursday (30 Dec) pushing 60 degrees for Des Moines. Not all Iowans were as lucky with those in north-eastern Iowa only in the mid 40s. The primary reason was the deep snow pack that existed prior to the strong push of warm air into the state. The featured chart presents an analysis of high temperature versus the snow depth present that morning. The relationship is clear! A common forecasting rule says the high can only reach 43 with 4+ inches of snow on the ground, the push of warm air was exceptionally strong which is why this rule didn't quite hold.

Voting:
Good: 26
Bad: 5

Tags:   snowcover  


Does the first snow stick around?

08 Dec 2010 05:47 AM
With folks in Ames and Des Moines anxiously waiting for our first snowfall of the season, one may wonder how long our new snowfall will stick around? The featured chart presents the date and amount of the first snowfall for Ames of the winter season. The dot's color represent how long measurable snow depth was observed after the initial snow fall. Last year, our first snow fall (around this date) stuck around until mid March! Most of the dots are in the 1-7 day range, so perhaps our first taste of snow will be brief like most years!

Voting:
Good: 16
Bad: 2

Tags:   snowcover   snow  


Generate This Chart on Website
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A repeat of last winter?

07 Dec 2010 05:47 AM
The forecast for the coming weekend looks to bring accumulating snow to central Iowa for the first time this season. The featured chart presents the daily snow depth reported near Ames for the previous winter seasons since Nov 1964. Last year certainly sticks out on this chart with deep snow throughout much of February. One also notes that once the snow arrived during the second week of December, it stuck around until mid March! Are we set to repeat this pattern?

Voting:
Good: 22
Bad: 5

Tags:   snowcover   2009  

Cold even without snow

06 Dec 2010 01:17 AM
For those of us in central Iowa still without snow, these very cold December days are typically what you would expect with snow on the ground. The featured chart presents the difference in daily high and low temperature when there was and was not snow on the ground. The cold weather will continue this week with a warm up to just above freezing not expected until the end of the week along with a chance of snow.

Voting:
Good: 24
Bad: 4

Tags:   snowcover  


Snow cover probabilities

19 Feb 2010 06:13 AM
The featured chart looks at the probability of having snow cover on a day during the winter contingent on having snow cover for a given date. Confused? In other words, if there is snow cover for this date, how likely was there also snow cover on March 1rst or December 25th of that same winter. One of the disappointing aspects of the chart are the clear month boundary effects as often the data was manually quality controlled a month at a time (the end of one month doesn't match the beginning of the next). The second week of March shows up nicely as an elevated chance of snow cover, but those events can then be associated with elevated probabilities in mid January.

Voting:
Good: 30
Bad: 26

Tags:   snowcover   climate  


How long will this take?

18 Feb 2010 06:10 AM
The featured chart plots the number of days it takes for a given snowfall depth to disappear. The depth is the maximum reported value during a period of snow cover. Rephrasing, how long does it take to get rid of the snow once we reach a local maximum of depth. If you hope that our last snowfall peaked our snow depth around 15 inches here in Ames, the chart would hint that perhaps we have another 30 days left before the snow disappears. Not good news. The dataset is separated by time of year and you can see the spring events (March-May) have a very short duration, which makes sense as temperatures are warming and solar angle increasing.

Voting:
Good: 23
Bad: 8

Tags:   snowcover  


Snow for everybody

15 Feb 2010 05:07 AM
The featured map is from the excellent NOAA NOHRC website showing snow water equivalent from Friday evening. The map shows every state in the lower 48 with some snow cover even the panhandle of Florida! Not shown are Hawaii and Alaska. While Alaska surely has snow cover now, it took a bit of detective work by Patrick Marsh to find snow in Hawaii. Regardless, it has been an exceptional winter for snow and more snow is currently falling and blowing in Iowa today.

Voting:
Good: 23
Bad: 11

Tags:   snowcover  


When there is snowcover on Christmas...

21 Dec 2009 06:10 AM
The featured chart looks at the daily frequency of having snowcover around the dates when there was an inch or more of snowcover on Christmas Day. Just as people wait until the last minute to complete shopping, sometimes Mother Nature waits till the last moment to make the Christmas white. The chart would indicate that roughly 20% of the white Christmas events occur due to a snowfall within 3 days of the 25th.

Voting:
Good: 11
Bad: 8

Tags:   christmas   snowcover  


First cold and snow cover

15 Dec 2009 06:08 AM
The featured chart looks at the presence of snow cover during the first fall/winter occurrence of a given low temperature based on data from the Ames COOP station. While having snow cover is not a requirement for really cold temperatures, it certainly is present more often than not for the first temperature below zero of the season.

Voting:
Good: 15
Bad: 6

Tags:   snowcover   lows  


Snow depth changes

26 Jan 2009 06:19 AM
The featured chart is the frequency of daily snow depth changes when there is snow on the ground based on 43 years of data from Ames. During the winter time, the most common thing to happen is no change. This plot would indicate that having the snowpack decrease is more likely than increase. The height of the stacked line chart indicates overall frequency of having snow on the ground. Light fluffy snow is in the forecast for this week, so more green than red for us.

Voting:
Good: 26
Bad: 9

Tags:   snowcover  


High temp line contoured and snowpack filled

Can tell where the snow is

22 Jan 2009 06:12 AM
The featured map is an analysis of reported snow depth and high temperature on Wednesday. The 32 degree isotherm nicely lines up with the boundary between deep snowpack and bare ground. It will be interesting to see how far into the snow field the warmer air can get today. Deep snow pack tends to create a very shallow layer of cold air that is difficult to mix warm air into or scour out.

Voting:
Good: 24
Bad: 6

Tags:   snowcover  


How warm can it get today?

26 Dec 2008 09:36 AM
The featured image is a scatter plot of next day high temperatures versus snow depth. The plot tries to answer the question how warm can it get the next day after having snow on the ground today. An old forecasting tip is that high temperatures rarely exceed 43 degrees with 4+ inches of snow on the ground. The 4 inch snow depth reference line on the chart indeed shows very few 43+ degree temperatures. With high temperatures forecasted in the 50s today, this will be exceptionally warm given our current snow pack!

Voting:
Good: 44
Bad: 16

Tags:   highs   snowcover  


Daily data required at least 4 events per day

Snow cover makes a difference

12 Dec 2008 06:20 AM
The featured chart is of daily average high and low temperatures for Ames based on observations since 1964. The overall average is shown in the faint color. The two other lines for daily highs and lows represent days on which snow cover was or was not reported. The effect of having snow cover is very clear with temperatures always lower on average. The simple reason for this is an increased albedo, which keeps the suns energy from warming the ground which warms our air! If you want warmer weather, get rid of the snow on the ground (chicken and egg process).

Voting:
Good: 49
Bad: 20

Tags:   snowcover  


Snow Depth Data

26 Nov 2008 06:13 AM
The featured chart shows the daily frequency of having snow on the ground and maximum snow depth based on data for Ames back to 1991. Based on this plot, the best chance of having snow on the ground is the end of January. The short term forecast does not have snow predicted and the weather on Thanksgiving looks very nice with highs in the 40s.

Voting:
Good: 67
Bad: 36

Tags:   snowcover  


9-12 March 2007 COOP reports

Any relationship here?

12 Mar 2007 07:39 AM
The featured plot is of daily high temperatures versus snow depths for locations in Iowa this past weekend. There is some ambiguity to the timing of the snow depth and high temperature measurement, but it is close enough for government work. The main point is to show the effect appreciable snow cover has on temperatures. While Southern Iowa enjoyed 60+ degrees on Sunday, most of Northern Iowa struggled in the low 40s.

Voting:
Good: 19
Bad: 3

Tags:   snowcover  


60 day chart for Nashua ISUAG site

Influence of snow

15 Dec 2005 07:46 AM
The featured plot charts daily solar radiation (red line) and average 4 inch soil temperatures (black line). Any idea why the black line has been mostly flat for December? The answer is snow! A blanket of snow acts just as that, a blanket. The ground's heat is trapped below and the ground is protected from the cold air above the ground. In fact, the ground remains rather warm which is no surprise for those folks who have been ripping up their yard with the snowplow.

Voting:
Good: 11
Bad: 1

Tags:   snowcover