Does winter fog mean spring flooding? It’s not precise science

It has been a stunning winter — in many senses of the word.

Even if you hate the cold and dark, you can’t deny that the sparkling snow and foggy mornings have felt a little magical.

Photo by Tea Storm Chasers 

Then, you start to shovel the next storm and wonder, where am I going to put all this as the mounds next to the driveway get taller and taller.

The next thought? When all this melts, we’re going to have a problem.

Peter Rogers, a meteorologist with the National Weather Service in Sioux Falls, said the first spring flooding outlook will be issued Feb. 9 and then updated every two weeks.

What does that have to do with the fog? Well, the Farmers Almanac predicts:

Summer fog for fair,
A winter fog for rain.
A fact most everywhere,
In valley or on plain.

If that’s true, and you combine it with the foot-plus of snow still on the ground in Sioux Falls, this spring could be a doozy. P.S. So far, it’s the fourth snowiest winter on record.

Photo by Tea Storm Chasers 

Rogers said he doesn’t exactly subscribe to the idea that a day of fog equals some other event in the future. The NWS sticks to a crystal ball of about a week ahead.

The office doesn’t keep detailed stats on fog, but the calm winds and moisture in low levels of the atmosphere are what have caused the blurry mornings. A little bit of wind would have blown it away.

Photo by Wes Eisenhauer

So normally, a fog that settles in overnight dissipates as the ground warms up. But when it stays cloudy and still, there’s no way to get that moisture out, and the fog can last later into the day.

That’s what we’ve been seeing.

“You’re getting that situation where the fog droplets are freezing overnight on contact, mostly on tree limbs and tree branches, and you get that crystallized structure that is really beautiful,” Rogers said.

It’s called rime icing, and it’s different from hoar frost.

Hoar frost is a buildup of delicate and feathery ice created when water vapor in the air condenses as ice on a surface. Rime icing is a buildup of ice when small liquid droplets freeze on contact. It typically forms in fog and grows toward a prevailing wind.

OK, so we have all this snow, and we’ve had all this fog – which may or may not predict rain – and we’re all starting to look to warmer weather.

It’s not quite the same as three years ago when Sioux Falls saw epic flooding, Rogers said. In 2019, deep snowpack combined with a lot of rain created the flooding, Rogers said.

“We are pretty dry, and much of the region is still in some status of drought,” he said. “Right now, from a soil perspective, it should be able to hold quite a bit of water.”

So is there any tie to the fog and the flooding? Probably not, he said.

“People might have those kind of sayings based on their experiences, but that isn’t something we would rely on,” he said. “In our business, we only forecast seven days out. We just take it day by day.”

The National Weather Service does forecast likelihoods for temperature and precipitation up to 14 days out — and there’s a little potential relief if you’re hoping for a warmup: