Harsh conditions and deep snow are frustrating rescue teams searching for a Twin Cities father and son who have been missing for nearly a week in a vast Colorado wilderness.

Making matters even worse, authorities have no idea where 18-year-old Evan McManus of St. Louis Park, and his father, Damian McManus, 51, might have gone, and days passed before anyone knew they were missing.

“We don’t have a primary search area because we don’t know where these two young men went to,” said Bill Barwick, of the nonprofit Alpine Rescue Team, whose trained mountaineers respond to wilderness emergencies. “We don’t have a direction of travel. We don’t know very much about what they had with them. Whatever trails they might have tried to take, there are easily four or five different trails. And their tracks have been covered over by five days of snow.”

Barwick said it has snowed nearly every day since the two were last heard from on Wednesday. Temperatures have dipped well below zero every night. And the winds have been blowing at 20 to 40 mph, said Barwick, who has been on the rescue team since 1984.

The search teams have included a scent dog, a helicopter and people on snowshoes, skies and snowmobiles. High winds forced the helicopter to end its search early Monday, Barwick said, and the threat of avalanches prevents search teams from going into some areas.

“We don’t know if they got caught in one of those,” he said. “Without an avalanche beacon [on them], there would be no way of finding them.”

Authorities began the search Sunday at Echo Lake, about two hours west of Denver, where the McManus car was found. The search area at the base of the 14,000-foot Mount Evans, could encompass as much as 20 square miles, Barwick said.

“We lose people in that area in the summer very frequently,” Barwick said. “Most of the time they walk out a little shamed-faced. Or, we go in and find out they sprained an ankle. But that’s an entirely different season. We’re in wintertime season here.”

And without a “starting point,” Barwick said. “They didn’t tell anyone where they were going. … We don’t know where to look. We don’t know if they had snow-travel equipment.” All we know is that they had breakfast on Wednesday morning.” Authorities found a receipt in the car, he said.

Last Wednesday, friends said, Evan, a St. Louis Park High School senior, sent a message to his girlfriend saying he and his father were going to “scale a mountain.” Barwick said the teen’s girlfriend said that the pair planned to walk for a couple of hours and then walk out.

But that was the last anyone heard from the father and son, who trekked to Colorado on a spur-of-the-moment spring break trip. Evan’s mother, Katherine, and his twin sister, spent their spring break in Mexico, said Andrea Bouzrara, who also went on the same Mexico trip with her daughter.

Katherine McManus got an e-mail from her husband last Tuesday, Bouzrara said. But McManus wasn’t alarmed that she hadn’t heard from her husband or son since then, figuring cellphone coverage in Mexico and in Colorado mountains was spotty, Bouzrara said. It wasn’t until Sunday, when headed to the airport in Mexico, that Katherine McManus found out that her husband and son hadn’t been heard from for days and hadn’t returned to the Twin Cities on Saturday as expected.

Back in Minnesota, Katherine McManus called authorities in Colorado and the search began. She and her daughter are now in Colorado, where the search is expected to resume Tuesday morning.

“The family feels very dismal but they’re trying to be hopeful,” Bouzrara said. “[They] believe that God is watching over them and hopefully they’re just sitting tight somewhere waiting to be rescued.”

Staff at the hotel where the father and son stayed knew something was amiss on Thursday because the pair hadn’t checked out. “And the maid said no one had been back in the room,” Bouzrara said. But authorities told the hotel staff that only a family member can file a missing persons report, Bouzrara said.

Now family and friends can only hope. Those searching for the pair know that a person with the right equipment and the right training could dig a snow cave and possibly survive the harsh conditions.

“Katherine says Damian is a guy who wouldn’t go off on a whim. He would have been prepared,” Bouzrara said. “Katherine said he doesn’t do anything without meticulously packing down to the millimeter.”

As the search continues and wait for news drags on, Bouzrara said her house is filled with high school teens who know the family. “It’s very tragic,” she said. “These are seniors. It’s supposed to be a happy time when they’re making college decisions, celebrating their senior year and being exited about graduating. … I have a whole house filled with girls mourning.”

“You kind of go up and down because you watch these news reports and you see how cold and snowy and blowy it is there,” Bouzrara said, her voice cracking as she stifled a cry. “And you think, oh my God, they’ve been in that for five days.”