The snow began around 1 p.m. local time Wednesday and was falling steadily in the middle of the afternoon as the Canadian moguls team arrived for practice.
Olympic officials expected between 2 and 4 inches of snow and said that should give them some cushion. The first freestyle competition is Saturday -- the women's moguls.
An uncommonly warm winter has forced officials to truck in snow from other parts of the mountain to maintain the integrity of the venue.
The biggest problem at Cypress has been forming the halfpipe, where two days of practice have been canceled.
Also on Wednesday, fog forced the first men's downhill training run to be canceled after only 42 of 87 scheduled racers completed the Olympic course.
Didier Cuche, of Switzerland, had the fastest time, but it wasn't immediately clear if the session would count. Olympic rules demand that all racers complete the course on the same day for it to stand as an official training run.
Race jury officials were meeting after abandoning racing because of poor visibility at 3 p.m. local time -- 41/2 hours after the session had begun earlier than scheduled because bad weather was expected.
"We delayed so long to see what the possibilities were," International Ski Federation official Mike Kertesz told The Associated Press. "Mother Nature is playing games with us."
Two more training sessions are scheduled for today and Friday, with the race Saturday. But more unfavorable weather is forecast.
"Looking at the existing possibilities, we were really trying with every effort to ensure that this training run went ahead," Kertesz said.
Officials halted the session after 40 racers had gone, then allowed two more to go before ordering a second delay when visibility higher up the mountain jeopardized skiers' safety.
Cuche, who has a broken right thumb, was fastest in 1 minute, 53.22 seconds. He was 0.29 seconds ahead of Canada's Robbie Dixon, who grew up racing in Whistler, British Columbia. Ambrosi Hoffman, of Switzerland, trailed by 0.55 in third.
Cuche had surgery Jan. 30 to fix his first metacarpal bone with a titanium plate and seven screws after falling in a World Cup giant slalom.
Whistler has a long-standing reputation for poor weather affecting races because of fronts coming in off the nearby Pacific Ocean.
World Cup race weekends were canceled in three consecutive seasons from 1996-98 before the venue was removed from the schedule. Whistler successfully returned to the circuit in 2008 in separate weekends of racing for men and women as test events for the Winter Olympics.
The women are to begin downhill training today on the adjoining Franz's Run. Their first medal race is Sunday's super-combined -- a downhill run followed by a slalom leg.
JONATHAN HAYWARD/ASSOCIATED PRESS
Cypress Mountain, the venue for freestyle skiing and snowboarding, was closed Wednesday because of high winds and dense fog. Early in the afternoon, a surprise snow storm hit, providing a welcome cushion. Freestyle skiing starts on Saturday.