UPDATE: Winter 2011-2012 - One of the Warmest in Recorded History Across the Area

Meteorological winter 2011-2012 (defined as the period from December – February) will likely be remembered as one of the warmest winters on record at many locations across central and northeastern South Dakota. This very mild winter can be attributed to several factors including below normal snowfall, lack of a persistent, deep snow cover, and few arctic airmass intrusions.

The tables below lists the warmest average temperature for the period December through February at Aberdeen, Pierre, Mobridge, and Watertown. Graphical displays for the observed temperature and departure from normal for all of South Dakota is also provided (courtesy of the High Plains Regional Climate Center).

One note is that 2012 is a leap year – such that the winter of 2011/2012 contained one more day in meteorological winter than a majority of the other years (91 days vs. 90 days). Leap year winters are annoated by an asterisk (*).

Aberdeen, SD (Normal DJF Temperature = 15.1F)

Rank	Average Temperature	Year
1	27.6	1931
2	25.6	1987
3	25.2	1983
4	24.7	1992*
5	23.1	2012*
6	22.9	1921
7	22.3	1998
8	21.9	2002
9	21.6	1944*
10	21.5	2006

Pierre, SD (Normal DJF Temperature = 22.0F)

Rank	Average Temperature	Year
1	30.2	1992*
2	30.0	1987
3	29.8	1983
4	29.2	2000
5	29.1	1998
6	28.4	1999
7	28.2	1981
8	27.3	2006, 1934
10	27.2	2002
11	26.9	2012*

Watertown, SD (Normal DJF Temperature = 15.4F)

Rank	Average Temperature	Year
1	25.6	1987
2	23.8	1992*
3	22.7	1921
4	22.6	2012*
5	22.4	2002, 1983
7	21.7	1998
8	21.3	2000
9	21.0	1919
10	20.4	1944*

Mobridge, SD (Normal DJF Temperature = 18.4F)

Rank	Average Temperature	Year
1	27.1	1992*
2	26.9	1987
3	25.9	1983
4	24.4	2002
5	24.3	2006
6	24.1	2000*
7	23.8	2012*
8	23.5	1981
9	22.7	1954
10	21.6	1976*

Figure 1: High Plains Regional Climate Center Average DJF Temperature:

Figure 2: High Plains Regional Climate Center DJF Depature from Normal Temperature:

The image below is a 1000m resolution, "true color" image from the MODIS satellite valid today - 1 February 2012. A couple interesting features noted on the image are described below:

Areas in "brown" are predominantly void of snow. As such - a vast majority of South Dakota is completely snow free! Obviously, this is quite rare for the 1st of February.
The "brown ground" is able to absorb much more solar energy, which allows temperatures to warm. This is a major reason why temperatures have remained above normal.
Residual areas of snowcover (white) are confined to the Black Hills region in western South Dakota and the Glacial Lakes region in northeastern South Dakota.
A large section of Lake Oahe north of Pierre is free of ice (dark blue color). Again, very rare for early February.

Mike Fowle - SOO