An unprecedented winter storm that is hammering  the Pacific Northwest coast with freezing rain and heavy snow has hampered the search for four hikers missing from Washington's Mount Rainier Park.

Mark Vucich, 37, of San Diego, and Michelle Trojanowski, 30, of Atlanta, were supposed to return Sunday from a camping trip on the Muir Snowfield, about 10,000 feet up, but have not been heard from in days.

The pair's car was found in a parking lot about halfway up the mountain, according to Mount Rainier National Park spokeswoman Patti Wold.

"They're still up there as far as we know," she said.  "We're hoping they [rescuers] stumble across them today.  If the weather is bad it may be that the team may not make it and have to come back."

Mount Rainier is about 70 miles southeast of Seattle, which was battered by snow and ice on Wednesday.  Mount Rainier was hit with snow over the weekend and temperatures continued to hover well below freezing.

A team of 10 Park Service staff set out today to travel the same route Vucich and Trojanowski would have taken, Wold said.

On Tuesday, the team was only able to conduct a limited search after conditions of zero visibility and 100 mph winds hampered their efforts.

The weather still isn't good up there," Wold said.  "We are doing what we can."

Meanwhile, two other climbers, an unidentified couple from Springfield, Ore., also remain missing after failing to return Monday from a summit attempt on the Disappointment Cleaver route.

Park officials believe both pairs of climbers chose to ride out the storm and wait for conditions to clear before returning.  All four are thought to be well-equipped with tents, sleeping bags and other cold weather gear.

Vucich's uncle told the U-T San Diego his nephew is an experienced hiker, but said the family remains worried.

"We hope he is hunkered down," Jack Anthony said. "It's not a good situation."

The missing hikers' families and park officials are hoping their story ends in a similar fashion to that of Yong Chun Kim, the 66-year-old snowshoer who was found alive on Mount Rainier after a two-day search.

Rescuers found Kim, of Tacoma, Wash., alive and well Monday afternoon after he fell down a steep slope Saturday while snowshoeing and became separated from his group.  Kim told park officials he burned dollar bills from his wallet to create warmth and stay alive.

National Park Service officials had to rescue Kim using a special Sno-Cat vehicle because the snowy and windy conditions prevented a helicopter rescue.

ABC News' Maria Nikias contributed to this report.

The Associated Press contributed to this report.