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Jeffrey D. Allred, Deseret Morning News
Researchers Zane Stephens, left, and Tim Wright get a temperature reading of minus 10 degrees Friday in Logan Canyon's Middle Sink \— one of Utah's coldest spots. Stephens first hiked to Middle Sink in 1982.

MIDDLE SINK, Cache County — This site in Logan Canyon is one of the two coldest places in Utah. The other is Peter Sink, just over a nearby ridge.

For seven of the year's 12 months, Middle Sink or the more difficult to reach and dangerous Peter Sink holds the record for coldest temperatures in the contiguous 48 states.

During a predawn visit Friday, Middle Sink was not cold enough to break more records. But at 10 degrees below zero, it wasn't exactly toasty.

Zane Stephens and Tim Wright, meteorology researchers, came here from their homes in Logan to check temperature calculations against the actual chill caused by an inversion inside the large, bowl-like feature. They invited the Deseret Morning News to join them. The site is at 7,600 feet elevation, 25 miles northeast of Logan in Logan Canyon.

The department head for industrial maintenance and safety management at Bridgerland Applied Technology College in Logan, Stephens teaches a night course in meteorology at Utah State University's Brigham City campus in the fall semester. Wright has temporarily paused working on his Ph.D. in meteorology and is teaching math at Bridgerland.

They calculate that around midnight, Middle Sink probably hit minus 40. But clouds moved in and affected the inversion that had trapped cold air close to the ground. The blanket of clouds reduced the amount of heat radiating into space and allowed relatively warmer air from higher reaches to mix with the bowl's icy atmosphere.

By 6:20 a.m., the temperature was up to a disappointing minus 10. Then it was minus 9 as the temperature continued to rise, Stephens noted, checking his thermometer.

Even without the intense frigidity that had been expected, Middle Sink presented unusual sensations. The blue-gray light was dim, showing distant trees and even more distant mountains. Somehow, despite the darkness, the pines displayed a hint of green.

Boots crunched and squeaked on the dry snow as the group hiked on a trail maybe 15 feet wide. The trail had been packed and ridged by a snow cat for the benefit of snowmobilers. Half a mile from a parking lot it reaches the lowest point of Middle Sink. Beneath its compacted surface, snow was piled 7 feet deep, as indicated by the tops of fence posts and signs of a known height.

Snow was crystallizing out of the atmosphere. Usually it was noticeable only as tiny cold points on exposed skin. But whenever a camera fired off its flash, for an instant the sharp, suspended dots caught the light and glittered everywhere.

Above the white depression a blurry half moon glowed through the cloud layer. A sign stuck out of the snow pointing the way to Garden City.

One of the unusual aspects of Middle Sink is what Stephens calls "a reverse tree line." Usually the tree line marks the altitude above which it's just too inhospitable for trees to grow; it's why tall mountains are bald.

But at Middle Sink, the trees at the rim of the bowl are normal. Just below, they begin to be stunted. Five or 10 feet lower, "they look like bushes." At the bottom of the bowl, no trees grow because of the cold weather.

The Sinks exhibit unusual chill even in the summer. Peter Sink never goes more than four days without a freeze at the bottom, Stephens said. "So the growing season's just four days or less, because you always get a freeze."

Stephens has been fascinated with weather since his second-grade teacher got him interested in the subject. Twenty-four years ago, when he was a freshman at USU, he got a job stocking merchandise at a Grand Central store. He made friends with another stock clerk, Mike Boman, who also was a weather fanatic. During breaks they would talk about the weather.

Knowing that Cache Valley's temperature drops severely during inversions, they wondered about conditions high in the mountains, where natural depressions might also undergo inversions. They began to look for cold places to study, like Dry Lake in Sardine Canyon.

"It's cold, but it's not that cold," Stephens said — maybe 15 or 20 degrees colder than Logan.

Boman suggested the Sinks, areas near the summit of Logan Canyon. Not far from Beaver Mountain Ski Resort, the Sinks are popular with snowmobilers.

Stephens and Boman hiked in to Middle Sink on Dec. 2, 1982. "There was a storm coming in, and we wanted to beat the storm," he said. "We knew it was going to clear out after the storm." A new coating of snow and the clear air that followed the storm might combine to cause cold temperatures. They parked on U.S.-89 above Middle Sink and walked down into the bowl.

"We just went right up to our necks in snow, every step." It took an hour to reach a fence halfway into the bowl. They tied the thermometer to the fence, using a clothes hanger to hold it in place above the snow. "We went back two days later and found out the low on Dec. 28 was about 38 below." Meanwhile, the station at USU showed 1 degree above zero, while downtown Logan was 10 below.

Later, they realized it had been even colder at Middle Sink. They had used an old-fashioned mercury thermometer. "Mercury freezes at 38 below zero," Stephens said.

"That got us excited." A similar bowl in the mountains of Austria sometimes reaches 60 below.

When an inversion forms, it is like a pool of cold air, he said. "Air is just like water," acting like a fluid.

When the cold air fills up the valley at night, it overflows at the top of the bowl and flows in. "At the bottom it is just colder and colder and colder."

In a windless period, an inversion concentrates the cold.

After Boman moved to Salt Lake City, Stephens continued the work alone. He approached the Utah Climate Center, based at USU, about his ideas. An assistant climatologist, Gaylen Ashcroft, encouraged him to study the location. They calculated how much the temperature should dip under certain conditions.

"I started to hike in at 5, 6 in the morning, before sunrise," carrying a research-quality thermometer. After the sun came up, the temperature would rise.

"I used to always go in straight down, on snowshoes," heading off from the highway and going across deep snow. Later, when the snow cat trail was started, it became much easier to reach Middle Sink from the parking lot, walking along the trail without snowshoes. The procedure is usually to check the temperature at the canyon's summit, then record a profile as the elevation drops. "It's pretty amazing how it changes," he said.

Walking alone, he would be concerned about twisting an ankle in a fall — at 50 below, a mishap could be deadly. Once, on snowshoes, he fell in deep powder and found himself upside-down. He struggled to regain his footing.

For a time he used an instrument shelter. In 1985, when the temperature turned out to be minus-64, he could not open the shelter because his gloves were too bulky. He couldn't even get the shelter's key out of his pocket.

"I just took my glove off, and I grabbed my key out of my pocket, put the key in the lock, turned it, opened the lock. Then I put the key back in my pocket and I pulled the lock off." He quickly put the glove back on.

"It all took about 15 seconds, and I had frostbite on my thumb."

When the thumb started to thaw, "it really hurt," Stephens said. "My thumb's still a little bit sensitive to the cold."

Twice he has experienced the numbing cold of 60 degrees below zero. At that temperature, "you can spit ice cubes." The snow's crunching underfoot becomes loud.

"It's about twice as loud as we heard today," he said. "The colder it gets, the louder it crunches."

When a TV meteorologist flew him to Peter Sink in a helicopter, the chopper landed on the snow crust. Stephens stepped out and plunged down 15 feet in the powder. He managed to climb a tree to safety.

"It was only about 5 below," he recalled, "but it was cold."

Not all of his adventures are scary.

He remembers going into the area one dark morning when a flare lit up the landscape from behind him. From a moment he worried that a nuclear attack had hit Hill Air Force Base. Instead, it was a "giant meteor" that blazed overhead, red and orange. It had a "big, long tail about halfway across the sky." On Feb. 1, 1985, the date Middle Sink reached minus-64, it was too dangerous to hike into Peter Sink to check the temperature. So Stephens retrieved the thermometer later and sent it to the Bureau of Standards in Washington, D.C. It registered minus-69.3, the second coldest ever recorded in the lower 48 states. (The lowest was at Roger's Pass, Mont., in January 1954, minus-70.)

Wright started working on his doctorate at USU and is thinking about transferring to the University of Utah when he has put aside more money.

He became interested in the Sinks six years ago. Don Jensen, the director of the Utah Climate Center at USU, "hired me to help out." Stephens was working at the center too, and the student asked him why the record low for Utah was 69 below at Peter Sinks.

"He proceeded to tell me the whole thing," said Wright, who was fascinated by the unusual weather. Ever since, they have worked together on the inversions.

"I came up with a mathematical model to essentially forecast the temperature, based on existing conditions," he said. It takes account of factors like temperature elsewhere, humidity, cloud cover or clear sky snow cover, how long darkness lasts that time of year.

"It works quite well," he said Friday, talking over the day's events by telephone.

"I just ran the calculations for this morning, and it came out to 10 below zero at the time we were there." The visit lasted from about 6:15 or 6:20 until shortly after 7 a.m., he said.

One ingredient that makes it more likely the temperature will drop exceptionally is the soft, powdery snow beloved by skiers, which falls abundantly at the Sinks. Powder insulates well and prevents the ground's warmth from reaching the atmosphere.

"It insulates even better than fiberglass insulation," he said. Stephens and Wright are serious about the research. "My most important thing is the inversion study," said Stephens.

But both admit they enjoy discovering that a new record has been set.

"I love it," Wright said. "It's fun."

E-mail: [email protected]