Duluth-Superior ski hills seed clouds with snow

• Radar map

National Weather Service radar picked up on small snow plumes created by snow-making operations on two ski areas near Duluth on Monday night into Tuesday morning. The more southern one is Mont du Lac. The northern one (toward the center of the image) is Spirit Mountain. Light southwest winds directed the plumes from southwest to northeast. Because they were making snow, the fine snow crystals activated low clouds to create microscale snow bands. About an inch of snow fell where the plumes lined up, but nowhere else. People in West Duluth and the Fond du Lac neighborhoods had to clean their cars off. (Photo from National Weather Service Duluth)

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• News Tribune article on new doppler from May

It wasn’t forecast to snow anywhere in the Duluth region Monday night or Tuesday morning, and it didn’t — except in a few West Duluth neighborhoods.

Parts of the Fond du Lac, upper Spirit Valley and as far as the western Lincoln Park neighborhoods saw up to an inch of new snow fall overnight.

“It started about 9 p.m. and snowed all night, very lightly but very persistent,” said Ron Williams, who lives in the Highland neighborhood of western Duluth. “It was enough that I had to put my vehicle into four-wheel drive to get up the steep hills.”

When he pulled into the parking lot at the Weather Service office in Duluth, where he serves as the port meteorologist tracking Lake Superior conditions, his co-workers were surprised to see fresh snow on his vehicle.

Forecasters went back and checked radar images from overnight to trace the snow. The source? Snowmaking machines at the Spirit Mountain and Mont du Lac ski areas.

The new enhanced “dual pole” Doppler radar at the National Weather Service is so good it clearly showed snow clouds created early Tuesday morning from the ski hills.

“I was amazed how well it showed up” on the radar, said Dean Packingham, a senior meteorologist at the Duluth Weather Service office.

A radar image from about 2:30 a.m. clearly shows precipitation falling north and east of both ski areas.

Packingham said he recalls the same phenomenon happening at least once before, about four or five years ago, when it was snowing in parts of West Duluth around Interstate 35 and nowhere else on a night when Spirit Mountain’s snowmakers were humming.

He’s not certain exactly what happens, but Packingham said the snowfall is not simply snow from the snowmaking machines blowing into town. Conditions had to be just right; the temperature at about 20 degrees and a light southwesterly wind, he said. Too much wind or temperatures too warm or too cold and the particles wouldn’t have made it up to the clouds.

Packingham said he thinks tiny particles from the snowmaking machines drifted up into low-hanging clouds, in effect seeding the clouds, spurring snowfall downwind of the ski hills for more than a mile. That’s farther than falling snow can blow from those machines, he said.

“There’s something going on with particles and the relatively low clouds, about 500 feet up or so.”

The News Tribune wrote about the new dual polarization Doppler radar in May. The Duluth Weather Service office received the upgrade last spring as part of a $50 million nationwide upgrade of federal radar systems. The new technology allows forecasters to better see into storms and especially plot rainfall and snowfall intensity while it’s happening.

Tags: west duluth, lincoln park, superior, news, snow, weather, skiing