Appling, 58, has spent a lifetime on Tioga Road. As a child, he watched his father drill holes in rock walls for dynamite during the route's late-1950s reconstruction. For the last 34 years he has plowed it — earning Appling the nickname "King of the Road."
"It takes a lot of spring openings to get to the point where you know what you're doing," Appling said.
"Instead of taking big bites out of the snow, it's better to take a bunch of small bites. Instead of go-
ing as fast as you can, it's better to go slower and let the machine eat it on its own."
Bulldozers rolling and pitching like ships on rough seas take the first passes at Tioga Road's drifts, knocking them down by half.
Massive rotors, the Tyrannosaurus rex of snowblowers, follow. With 5-foot wheels corseted in doughnut-sized chain link and a maw of steel blades, the 53,000-pound machines gobble and spew out 500 tons of snow per hour in long arcs.
Mile by mile, the machines carve a two-lane chute through forests, around tight curves and across white-knuckle precipices where the road's path isn't obvious and a wrong move could mean falling into the abyss.
The dangers come from above as well. Canapary, Lynds and Esquivel make up one of two teams that monitor Tioga Road's 26 avalanche zones — slopes pitched between 30 degrees and 45 degrees, which collect snow through the winter much as a coiled spring stores energy.
They camp in the backcountry for days at a time. They dig pits in slide paths to study the multiple layers of frozen and loose snow the way geologists would pore over the strata of a canyon wall.
The stability of these slopes changes daily, even hourly. Rapid warming, rain and new or blowing snow add weight, causing slabs to fracture and roar down at speeds approaching 80 mph.
"Predicting an avalanche is like predicting an earthquake," Lynds said.
They nudge the process along with explosives — sticks of duct-taped charges and a mixture of ammonium nitrate and fuel oil poured into plastic bags with an old coffee can.
Cantilevered cornices are blasted from ridges. Bombs buried along with charcoal send up plumes of fine silt across slide paths; the blackened snow absorbs heat and melts quicker. When a slope is too unstable to climb, the crew rappels from cliff tops and tosses the bombs.
All three men have spent much of their working lives outdoors — repairing trails, building bridges and operating heavy equipment. (Canapary and his wife honeymooned in a snow cave.)
Their work is exacting and exhausting — and the consequence of a deadly 1995 avalanche.
It was mid-June and the bulldozers had reached Olmsted Point with a couple of weeks' work still to go. Barry Hance, 43, was a veteran road crew supervisor who knew the hazards. Hance decided to keep things moving by clearing the most treacherous 300 yards of Tioga Road himself.
"He wasn't even supposed to be working that day," Lynds said. "But he was the boss. He was the most skilled."
In an instant, a torrent of snow raced down the slope, swallowed Hance's bulldozer and killed him.
An expert in avalanche control was hired to study Tioga Road's slide paths and overhaul the park's attack plan. Teams were formed and trained in snow science — how to size up risks and avoid catastrophes.
All workers are now required to take an annual avalanche survival course. They learn to search for victims with electronic beacons and metal probes. They practice shoveling and extraction techniques. They learn that nine of 10 avalanche victims live if reached within 15 minutes — and that survival rates fall off a cliff after that.
"If you get caught in a slide, try to swim on the surface to keep from being buried," Esquivel told a class of 15 park employees, most of them beefy guys with beards and bear-paw hands. "Yell loudly so other people can see where you are. Then close your mouth."
Esquivel and Lynds dig their crampons into the slope and make their way up to Canapary with the dexterity of mountain goats, despite their heavy loads.
They work fast, loading the holes with explosives and charcoal and connecting the charges to one another. A strip of sunlight appears on the top of the cliff and inches down toward them.
Soon the snow sparkles as if strewn with diamonds, and the soft gurgling of percolating water begins.
Canapary spools out cord to a spot a couple hundred yards away and attaches it to an igniter.
"If anything comes flying at us, dive in there," he said, pointing to a spot behind a boulder and a juniper tree.
"Clear the area! Blasting!" he yells down the valley, just in case there are backcountry skiers nearby.
"FIRE IN THE HOLE!"
With the push of a button the silence is shattered. The slope underfoot trembles as if rocked by an earthquake. Fire and charcoal fill the sky. And waves of concussion roll through the mountains toward Yosemite Valley, winter's echo heralding summer's approach.
Interactive: Four seasons in Yosemite