Plumbing the powdery depths

Jeff Wheeler, Star Tribune

Assistant state climatologist Pete Boulay measured the snowfall in his Maplewood back yard Wednesday evening. He used a metal ruler to measure the snow that had accumulated on top of a board covered in plastic.

Climatologist Pete Boulay created a low-tech tool that is the industry standard for measuring snow.

By BILL McAULIFFE, Star Tribune

Last update: December 29, 2007 - 10:18 PM

Pete Boulay measures snow. On wintry weeks like the one past, he slips on his boots and jacket each morning, trudges out to the back yard of his Maplewood home and, in effect, measures how deep many conversations across Minnesota will be that day.

"It becomes a habit, like having coffee," said Boulay, who, backed up by his wife, Nancy, has been measuring the snow since 1999.

Pete Boulay is well-known in Minnesota in his role as an assistant state climatologist. But his influence is broader in weather circles because he helped improve the low-tech method that has long been the standard for measuring snow on the ground.

In the winter of 2001-02, Boulay made a discovery while working on a state Department of Natural Resources project to monitor snowfall inland from the North Shore of Lake Superior. He and his colleagues found that a plastic-covered board was better for capturing snow than the customary painted wood, which tended to warp or chip and change color, possibly causing some snow to melt.

Now the plastic board is in use by several thousand volunteers for the National Weather Service across the United States. More recently the thin white board, 16 inches by 2 feet, played a starring role in a National Oceanic and Atmospheric Administration snow-measuring training video.

"I'd call it a Boulay board," said Craig Edwards, retired meteorologist-in-charge at the National Weather Service office in Chanhassen, where several such boards are used for official snow measurements.

Indeed, the plastic covering is symbolic of efforts to refine one of the trickier elements of weather observation -- getting accurate measurements of snow.

Nationally, snow measurements might be 10 percent off the mark, said Nolan Doesken, state climatologist for Colorado and a national expert on snow. That's the result of wind blowing snow around, as well as the varying abilities of the volunteers, who tend to be trained in the summer, Doesken said.

Snow measurements can be more than just something to argue about. Plowing contracts and insurance policies are often based on snow readings. (Doesken said he has heard of insurance companies being on the alert to bribes for inflated snow measurements.) Snowmobilers and skiers build weekend plans around snow reports. Calculations of the water content of snow -- done by satellite and by gamma ray sensors in aircraft as well as by volunteers melting snow in rain gauges with hot water -- form the basis of spring flood forecasts.

For Boulay, who took weather readings as a Boy Scout growing up in Maplewood and later graduated from St. Cloud State University with degrees in meteorology and broadcasting, snow measuring is something far more personal.

"It's kind of like a weather diary for me," he said. His record, he said, "reminds me of what I was doing that day."

The constants are these: Each morning he walks out to the yard, where his garage and a tree provide some windbreaks so snow can fall more evenly, and measures the new snow on his board with an official National Weather Service ruler (which breaks inches into tenths). He notes the amount. That's the 24-hour snowfall total.

Then he wipes that board clean and replaces it on the same spot on the ground. Next, he measures the current total snow depth on an adjacent board. He'll also take a "core sample" from the yard to melt to determine moisture content.

The greatest hazards to accurate measurements in his yard, Boulay said, are his two boys and his dog, who like to play in the snow. But so far this year he's been pretty close to the Twin Cities official totals, even though his home is about 12 miles northeast of Minneapolis-St. Paul International Airport.

Recently the weather service has experimented with sonic sensors that measure snow depth, including fresh snow, every five seconds. The devices, still being tested, might someday be used to establish an automated network of snow readers more extensive than the volunteer force now at work, said Tim Kearns, data acquisition program manager at the National Weather Service office in Aberdeen, S.D., where three of the sonic sensors are in use. They might also provide a regular stream of online snow measurements the public might access at any time, Kearns added.

For now, "there isn't a good automatic way to measure snow," Boulay contended. "You still need a person."

Bill McAuliffe • 612-673-7646

Recent Local + Metro stories

Bombings mar effort to hand over primary security role to Iraqis - December 29, 2007

Bombings mar effort to hand over primary security role to Iraqis - A string of explosions in Mosul killed 14 people, but U.S. and Iraqi officials voiced confidence in the transition. More