(CNN) -- Rescuers hoping to find two hikers missing on the frigid slopes of Oregon's Mount Hood faced worsening weather conditions Monday night as forecasters predicted white-out conditions that could severely hinder search efforts.
"Starting tonight and through tomorrow, it's going to be windy, and white-out conditions are going to be highly likely," said Scott Weishaar of the National Weather Service.
Up to 2 feet of snow is expected to fall Monday night into Tuesday at the elevation where rescuers are searching for any signs of Anthony Vietti, 24, and Katie Nolan, 29, who have been missing since early Friday.
A third hiker who was with them, 26-year-old Luke Gullberg, was found dead Saturday. A state deputy medical examiner said Monday that the cause was hypothermia, CNN affiliate KGW reported.
Rescue crews took advantage of a brief break in the weather Monday afternoon to search previously unreachable higher elevations of the mountain.
"Unfortunately, we did not detect anything out of the ordinary as far as gear or people," searcher Monte Smith told reporters. "With increasing snowfall coming down, it's going to make everything that much harder."
Weishaar said another series of storms Wednesday will dump another 10 inches to 18 inches of snow in the area, with temperatures in the low- to mid-20s. Snow was expected to start falling at 5 p.m. PT (8 p.m. ET).
"We only have today. We know we only have today," said Vietti's aunt, Teri Preiss.
Rescuers said they were putting no time limit on their efforts, and would do all they could despite the grim forecast.
"This remains a search and rescue mission," Clackamas County Detective Jim Strovink told an afternoon news conference. "We have two experienced climbers who were well-equipped. We have an obligation to continue on and that's what we're going to do. We owe that to the family and we owe that to the climbers."
Search crews will meet Tuesday morning to assess weather conditions and determine how to proceed, the Clackamas County Sheriff's Office said after ending search efforts for the day Monday.
Ground efforts have been severely hampered by avalanche conditions, which kept rescuers from accessing the parts of the mountain they wanted to reach early Monday morning. The avalanche threat also thwarted ground searches Sunday, authorities said.
Searchers were also examining high-resolution photographs taken by aerial surveillance teams, hoping to find any sign of life.
Capt. Chris Bernard of the U.S. Air Force 304th Rescue Squadron said infrared devices are being used as well. If the hikers have gone into a snow cave and have an air vent, the devices could pick up a heat signature, he said.
When the three hikers set out at about 1 a.m. Friday (4 a.m. ET), they were planning a fairly easy, "semi-technical" hike in which they would come down the south side of the mountain, said Deputy Scott Meyers of the Clackamas County Sheriff's Office.
Preiss said pictures show "it was a perfect climbing day, absolutely clear."
The three hikers sent out a message in advance saying that conditions were "absolutely perfect" and that they would be back by late afternoon, she said.
"These kids loved, loved climbing. All three of them. They climbed together often. They climbed hard mountains together before. And they did it successfully and well. And they were careful climbers," Preiss said.
Dr. Christopher Young with the state medical examiner's office said Gullberg had suffered minor injuries -- cuts, scrapes and bruises -- apparently caused by a fall, KGW reported. Investigators believe the 26-year-old was able to move himself after falling an unknown distance.
"Accidents can happen -- and it happened here," Preiss said, describing Gullberg as a "passionate young man" who was very well-prepared for all his hikes.
David Vahey, a family friend of the Viettis, said, "We know that they, all three, loved hiking and they all three loved Jesus. And we just want to ask for prayer."
The three hikers are from the Pacific Northwest. Vietti's home is Longview, Washington; Nolan's is Portland, Oregon. Gullberg was from Des Moines, Washington.
Gullberg's MySpace page is filled with photos of him hiking in various places. A friend wrote Saturday on the page, "I love you dude and miss you."
His grandmother, Marjorie Gullberg, said she will miss his smile. "He was just like my son. He did everything for me," CNN affiliate KPTV quoted her saying.
Dennis Simons, a chaplain for the fire and police departments in the city of Sandy, Oregon, spent time with the families of all three on Sunday. "They're grieving and hoping. There are thousands of people around the world praying that Katie and Anthony will be found alive," he told reporters, holding back tears.
The mountain rises 11,239 feet above sea level, with a vast base that stretches over 92 miles (148 km). It is the highest mountain in Oregon. Mount Hood is a dormant volcano with steam constantly spewing from holes, according to the Web site mthood.info.
Gullberg's death is the latest of many accidents on Mount Hood, KPTV reported. The worst occurred in May 1986 when nine people, including seven students from Oregon Episcopal School, died after they dug a snow cave during a sudden storm.