Steve Thompson watches clouds swirl over Wisconsin in a series of satellite photos that flash across one of the five computer monitors on his desk.

Weather systems usually come from the west, but today the atmosphere is anomalous, and it’s pushing the cloud cover back over the state.

On another screen, computer-generated models show how the atmosphere might act two days in the future.

Thompson’s job is to figure out if those clouds will cover his 28-county region of western Wisconsin, Minnesota and Iowa and how that might affect the weather. The model shows relative humidity changing from 15 percent to 90 percent within a few miles.

The computer shows probabilities. Thompson has more than three decades of experience — the forecaster’s trump card.

On yet another screen, in a graphic forecasting program, he traces a finger of clouds over Richland, Grant and Crawford counties.

Thompson is among nine forecasters who work around the clock at the National Weather Service office on a ridge just north of Grandad Bluff.

He is always conscious of the Weather Service’s mission: protect lives and property.

“He doesn’t want anything bad to happen on his watch,” said Todd Shea, the warning outreach meteorologist at the La Crosse office. In the 1980s, before the La Crosse office was staffed 24 hours, Thompson would come in whenever bad weather threatened, Shea said.

When his shift ends at 8 a.m. Thursday, Thompson will retire after 28 years of predicting the area’s weather.

In three decades, he has blown more forecasts than he can count.

He still remembers the January day 11 years ago when he predicted an inch of snow. Eight inches fell along the Interstate 90 corridor in what his fellow forecasters still call “the Onalaska Eight.”

He redeemed himself seven months later.

Thompson was the radar operator July 8, 1999. All the data said conditions were ripe for a tornado.

As afternoon turned to evening, red-blue couplets appeared on his radar screen — the signature of a funnel cloud over western Winona County. Trained storm spotters called in corroborating reports.

Thompson issued a tornado warning at 7 p.m. for Lewiston, Minn. Twenty minutes later, an F2 tornado plowed through town, destroying four homes and damaging 26.

No one was seriously injured.

On this day, he isn’t expecting the high-impact weather that brews during Midwestern summers. Or even the “slow fuse” of a snowstorm. Those clouds might mean only a few degrees difference in temperature.

But Thompson knows people depend on his forecast to make decisions.

Power companies that must constantly match output to demand are weather hawks.

People turn on more lights on cloudy mornings. When the temperature drops five degrees in the winter, Dairyland Power has to come up with another 25 megawatts to power all those heaters.

“Someone could be counting on that,” Thompson said. “Whether it’s somebody cutting hay, or planning a flight or distributing electricity.”

It’s a lot to think about before he hits the “Enter” key.

Thompson is 55 and slim. He has glasses and a bushy white mustache and drawls his words carefully.

As a 6-year-old in Greensboro, N.C., he built a backyard weather station, with a rain gauge, thermometer and even an anemometer made with plastic butter cups on wood dowels to measure the wind speed.

He started flying at 15 and got his pilot’s license two years later. Though he’s never owned a plane, he indulges his hobby when he can, volunteering once a year for an “angel flight” to provide free transport for medical patients.

Thompson attended North Carolina State University on an ROTC scholarship and was commissioned as an Air Force lieutenant in 1977. He was a forecaster for the Strategic Air Command in Nebraska before landing his National Weather Service job.

A devout Christian, he plans to spend retirement ministering to young men through the Evangelical Free Church in La Crescent, Minn. For him, the gospel is a spiritual weather warning: “Here’s what you need to do to save your life.”

In forecasting, confidence is like a funnel. The further out you go, the less certain you are.

“The only thing certain is there will be uncertainty,” Thompson says.

Thompson is confident in those clouds.

But his forecast now clashes with the Milwaukee office’s projections for counties to the east. He swivels to another screen logged into a National Weather Service chat room. He sends a message to his colleagues in Davenport, Iowa, and Milwaukee suggesting they increase their cloud cover projections.

A few minutes later, another meteorologist agrees. The forecasts will match.

Through the window, Thompson notices a band of alto cumulus clouds drifting in from the north.