A spring-like air mass has surged into Upper Michigan ahead of low pressure that is working northeastward toward Minnesota. Upper Michigan is in the warm sector of the system with a general south component to the wind. Temperatures have risen into the 60s over interior locations. However, winds are not all that strong, so the wind shifted to the north at some locations near Lake Superior. For instance, while it was well into the 60s in Negaunee, along the lakeshore at the Coast Guard weather station, the wind was out of the north and the temperature was only 40 degrees.
With the warmth has come moisture for showers and thunderstorms. They developed last night over the western U.P. where Calumet and Mohawk in the Copper Country each received over an inch of rain. This afternoon a strong thunderstorm developed over northeastern Delta County and prompted a Severe Thunderstorm Warning for parts of Schoolcraft and Luce Counties. The storm quickly weakened and no severe weather reports were received.
There is a good chance of more showers and thunderstorms tonight. In typical warm season fashion, coverage will likely be spotty with some areas receiving heavy rain while others get little or none. There is still a chance of some briefly severe storms with strong winds and hail. This will be especially true into this evening, and then the primary threat will be heavy rain and lightning.
The likelihood of showers and thunderstorms will continue over the eastern half of Upper Michigan into Friday morning. Then drier air working in from the west will probably lead to partial clearing. Tonight??s low temperatures should be almost summery with most areas staying at 50 degrees or above. With the warm start, temperatures may be the highest so far this season over a good share of Upper Michigan on Friday. Highs could reach 70, especially over interior sections of the western half of the U.P.
Right now Saturday looks like a fine day with a good deal of sunshine and mild air. Highs will likely reach around 60 into the 60s, but it will be much cooler, especially in the afternoon particularly near Lake Superior. Sunday may see the return of unsettled weather with a chance of showers developing as another upper-air trough reloads over the Rockies and Plains.