The 2017 eclipse in review

Radar loop showing precipitation advancing across southern Minnesota on August 21, 2017. First half of loop was during the partial eclipse.

Loop courtesy of College of Dupage 

 

The much anticipated 2017 solar eclipse occurred amid a mix of clouds, rain, heavy thunderstorms, and limited clearing in Minnesota.

Morning thunderstorms in southern and western Minnesota had placed a heavy overcast across much of of the state. At 11:45 a.m. CDT, as the eclipse was beginning, strong thunderstorms with intense rains were affecting the Minnesota River valley, and parts of far southwestern Minnesota along the Iowa border. Light to moderate precipitation was falling across the Willmar and St. Cloud areas. Cloud-filtered sunlight was visible across the Twin Cities area, and predominantly sunny conditions were noted across the southeastern 1/4 of the state.

The clouds and rain advanced eastward, and only far southeastern Minnesota was able to experience the eclipse without significant interference from cloud cover. Almost everywhere else, dense clouds and rain made for poor viewing conditions and certainly made it difficult to identify the effect of the eclipse, versus that of the overcast.

Despite the less-than-ideal visual conditions, the eclipse had a notable effect on Minnesota's weather. On a typical day, the sunlight passes directly to the earth, but any clouds present will filter some of that sunlight. During the eclipse, however, Minnesota had 70% to 90% of the direct sunlight blocked by the moon, before that light even reached the clouds, resulting in far less than usual mid-day heating at the surface. As a result, locations with cloudy and clear skies alike saw temperatures drop between noon and 2 p.m.. At Rochester, skies were clear through the majority of the eclipse, and temperatures fell by five degrees in just two hours.