Around here, snowfall predictions are a crapshoot

It was Tuesday when the National Weather Service issued a winter storm watch for the system expected to wallop Colorado Thursday.

At that time, the storm was rushing across British Columbia a thousand miles away, but the weather service's forecasters and computer models could already see it drawing a bead on our state.

"We've been advertising this for several days," said Tom Magnuson, warning coordination meteorologist for the National Weather Service's Pueblo office, on Wednesday. "Today, we've got to issue a warning, decide what we're going to do."
Much of Colorado is going to get pounded, Magnuson said. The question is, will Colorado Springs?

With the Palmer Divide to the north of us and Pikes Peak to the west, this area is as tricky to forecast as anywhere in the country.

"You want to know why it's so hard to forecast? You've got that big rock sitting there," said Steve Hodanish, a senior forecaster for the weather service. "Here in Colorado, terrain rules."

At the surface level, a low pressure zone near New Mexico will suck the air down the Front Range, producing strong northerly winds. Higher up in the atmosphere, the low pressure should send wind and moisture spinning in from the east.

"It's pretty complicated what's going on," Magnuson said.

The air cools at higher elevations and it can hold less moisture, causing precipitation.

Today, that means snow. The Palmer Divide, Palmer Lake and Monument could see a foot or more.

But as that air descends into Colorado Springs, it warms and begins to hold onto its moisture. That's why Monument often gets blanketed while Fountain is bare and dry. The forecasters call Colorado Springs and Pueblo the "brown patch" because we get so little precipitation here.

"It goes downhill, it dries out," Hodanish said. "Colorado Springs is one of the few places in the nation, if not the world, where there's so much variability in one area."

Predicting snowfall totals for Colorado Springs is a crapshoot: How far south that precipitation lasts is often anyone's guess. Add to that the potential for a narrow band of heavy snow to suddenly develop and, on Wednesday morning, none of the meteorologists could predict for sure what's going to fall where.

"Here in Pueblo, we could get an inch or 2, or we could get a foot," Magnuson said.

There are 21 employees in the weather service's brick office building next to the Pueblo Memorial Airport. Ten of those are operational forecasters, of whom two are on duty at all times. One focuses on the next 24 hours, the other looks seven days out. On Wednesday, Hodanish had the long-term duties, while general forecaster John Kalina was handling the short-term forecast.

"He has to pull the trigger," Hodanish said, meaning Kalina would decide what areas to issue a winter storm warning for and when to start it.

The forecasters sit at desks covered with four or more computer monitors, each showing different data and computer models. They play the computer simulations forward and back, using different models and their own experience and intuition to predict what's going to happen. As of Wednesday, the major models agreed that Colorado Springs was in line for a healthy dose of snow - probably 4 to 8 inches.

Looking further out, the models diverged. In one, Prowers County was getting buried on Friday with 10 inches of snow. The other showed dry skies.

"If this solution is correct instead of this one, they're going to get hammered," Magnuson said. "That's the conundrum of Friday evening. That's why there's humans trying to figure this stuff out."

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NATIONAL WEATHER SERVICE

See forecasts and data from the National Weather Service's Pueblo office at: www.crh.noaa.gov/pub