Posted at: 04/25/2013 9:29 PM
Updated at: 05/28/2013 12:52 PM
It's been a tale of extremes between Spring 2012 and Spring 2013. The former, one of the warmest and driest ever recorded and the latter cold and wet. So what's the difference? Why are these so different?
In 2012, at top right, a very strong, persistent dome of high pressure kept the jet stream shifted way to our north, letting all the warm air into the upper midwest, and the eastern 2/3rds of the country.
In 2013, at middle right, we've seen a very recognizable pattern from the northwest, one that is normally found during the depths of winter. A persistent blocking pattern set up way off in the Pacific kept that active storm track hitting the upper midwest, straight from Alberta, Canada.
Temperatures for the last 30 days have been well below normal. As the image at the left shows, that reading is about 8° too cool averaging about 35°. But it's not just us. The Dakotas and outside of our corner of SE Minnesota, Minnesota has been pummeled with snowfall well into April attributing to the well below normal temps. Even the Gulf Coast is getting in on the action.
At bottom right, High temperatures for April are listed. Only two days this April have had temperatures above normal, April 6th and April 8th. April 6th provided us with our warmest day of the year so far at 58°. Since then, the last three weeks have been marred by this cool setup.
It's a pattern that has kept our first 60° reading away, a number we normally see somewhere around March 22nd, a full month late. In fact so late, it will tie the record set back on April 25th, 1951 as the latest first 60° temperature reading of the year.
Finally a bit of relief is heading our way. Instead of the jet stream kinked way down to the south letting the cold air in, it lifts northward as the image at right shows, letting warmth finally emerge. Temperatures on Friday will cruise well into the 60s. The 70s are expected Sunday through Tuesday.
Will the warm pattern last? It's not looking too promising as another batch of cooler air will blast in at the end of next week.