The temperature in northeastern Minnesota over the weekend dropped 43 degrees in 12 hours thanks to air coming off of Lake Superior.
The National Weather Service in Duluth tweeted a graph Sunday of the crazy temperature drop:
And meteorologist Sven Sundgaard tweeted a graphic that shows the cold air pushing across much of Minnesota:
So why did this happen?
Temperatures in the Northland were in the 70s and 80s Saturday but crashed hard thanks to the shallow wedge of cold air coming off Lake Superior, which forced the warm air up about 4,500 feet, the NWS says.
While it was in the 40s on Sunday on the ground in Duluth it was 60 degrees about 4,500 feet above the city, NWS. And the gusty northeast winds send that cold air inland.
Sundgaard explains the science behind this further:
"Basically, cold air gets very dense this time of year sitting over Lake Superior (water temps are still in the upper 30s mid-lake to 40s) when temps inland get as warm as they’ve been this early. There was also cold air piled up north of Lake Superior (illustrated on the map below). They sort of combined forces late Saturday into Sunday. Lake Superior being the conduit for cold air to sneak in like a ‘back door' cold front. With cold, dense air already sitting over Lake Superior, the cold air north of the lake toward southern Hudson Bay only needed to make contact and it was like a wind tunnel pushing across the lake."
What happened over the weekend, with cold air from Lake Superior pushing across much of the state, does not happen very often.
"It’s not common to see air over Lake Superior penetrate this far south (it did reach most of the metro by late Sunday), but we had the perfect set up: high pressure sitting over that southern tip of Hudson Bay pushing air outward, and a still cold Lake Superior," Sundgaard said.
The NWS says southerly winds on Monday will help bring some of the warmer air back to the Northland, with highs in the 70s (if you're away from the lake, that is).