It's amazing to think that just 2 years ago, we would hit 80° in the month of March… something that hadn't happened in decades. A 4 day stretch from March 16th – 19th 2012 was the warmest 4 day stretch in March in history with high temperatures of 79°, 80°, 79°, and 79°. These 4 days all set daily record highs which had been around for years and was just 3° shy of the warmest March day ever. Not to mention, that St. Patrick's Day was the earliest 80° day ever in a calendar year. These 4 days were just the highlight of the warmest March on record in Minnesota and in 27 other states that can be seen below.
So why did it happen in 2012 and not this year??
It was literally the perfect conditions. If you can recall, that was the year with no winter. Very little snow and very warm conditions with all of the cold air staying up in Canada and the North Pole. This March heat wave was the sum of what had already occurred in the months leading up to it. 1st off; we were enormously dry. This leads to naturally warmer temperatures because dry ground heats up faster and more efficiently. 2nd; there was no snow on the ground anywhere south of us, or in the state for that matter. As you know, snow has a drastic cooling effect on temperatures. 3rd; the ground temperatures were very warm for that time of year because of the lack of cold and snow over the winter. 4th; a large trough dove into the west coast driving the jet stream out ahead of it further north leading to southerly flow at the surface. This allowed very warm air in the southeast to shift northward and bring 70's all the way into Canada. You can see the overall state of the atmosphere in the image below.
This graphic shows the large low pressure (the red L) diving into the West Coast with high pressure (the big H) sitting in the perfect position right over Florida to maximize southerly flow and our warm air advection over much of the country as the jet stream (the pink line) is shoved to the north. Whew… that was a mouth full!
Can this happen again? Sure… but the likelihood of anything like this happening again in March in our lifetime is almost zero. So 80's on the 7-day forecast likely won't appear for a while. If we are lucky, maybe we can get one before April is over, but I'm looking forward to the 60's and 70's!