Sunday, March 15, 2015 was a remarkable day temperature-wise especially in portions of southern and eastern North Dakota. The North Dakota Agricultural Weather Network (NDAWN) stations maximum temperatures on March 15 are presented below. The warmest temperature recorded that day across the mesonet was in Hettinger with a high of 78°. Although still mild for the time of year, it was significantly cooler across much of northern North Dakota with maximums in the 50s. There was a cold front moving across the area during the day and locations with highs in the 50s and even 60s in many cases recorded maximums early in the day or temperatures held steady much of the afternoon once that cold front moved across those areas.
The locations that stayed in the warm air throughout the day, the timing was perfect for an exceptionally mild day for so early in the season. To achieve such warmth so early in the season a combination of things aligned just perfectly.
1. The lack of snow cover over the winter quickly melted with the warmer temperatures a good week before March 15. The warm air mass that was in place through the week without any snow cover allowed the top few inches of the soil to thaw which aids in heating the lowest levels of the atmosphere.
2. The series of mild days leading up to March 15 also allowed that top layer of soil to dry, which is another ingredient for warmth.
3. The aforementioned cold front as it was moving across North Dakota led to a downward motion of the atmosphere ahead of that front. This compression of the lower layers of the atmosphere is yet another element that aids in the development of warmer temperatures.
This trifecta of circumstances led not only to some daily records, but to other “so early in the” season temperature records as well. Both Fargo and Grand Forks set records for the earliest 70 degree day of spring. Although it was the record for the earliest such occurrence on record, it should be noted it was only 1 day earlier than the previous earliest 70° record set in 2012 and only two days earlier then the first 70° in 1910.
For stations with records dating back to at least 1930, record maximums for March 15 were tied or broken in the following locations in North Dakota.
Not only were record maximums recorded at several locations in North Dakota, but several record maximum minimums were also also established. Such records are presented below from station with records dating back to at least 1930.
Fargo, Grand Forks, Bismarck and Williston all set standards for the warmest low temperature for so early in the season. Plus in Fargo the 48° low that day is tied for the 3rd warmest minimum of any March day since 1881 when records began for that location.
The warmth of the the second week in March 2015 was impressive, yet, there are no signs that any temperatures near those levels will be achieved again the rest of the month. So unlike March 2012 or 1910, it will not persist through much of the month like those two years, but instead, be similar to what happened in the first week of March, 2000, which is it was just a taste of real spring that will not take hold for several more weeks.