SKIERS GET LATER LAST CHANCE AFTER STRONG EL NINO WINTER : MAMMOTH TO STAY OPEN UNTIL JULY FIREWORKS.

Byline: BRETT PAULY

Mention spring skiing and the images that come to mind are icy mornings, slushy afternoons, corn snow, bottoms of skis shredded by rocky thin spots, T-shirts and gobs of sunscreen.

How about powder on top of a 16-foot base? Down parkas? Dare we say frostbite?

Anything is possible in this record-setting El Nino year that is pushing winter's wonderland into May - and beyond - at regional ski and snowboard resorts.

``As you can see, these are really winter snow conditions,'' Mark Pierce of Hermosa Beach said Friday at the summit of 11,053-foot Mammoth Mountain.

The thermometer read 18 degrees. The snow was nearly 200 inches deep and included 3 inches that dropped the night before. And there were no lift lines; you could literally ski right up to the chair.

``When spring rolls around, people forget about skiing. They go to the beach,'' said Pierce, who was visiting the region with friends for their annual ``Fat Man Triathlon'' - golfing, skiing and fishing. ``But the snow is still good, the crowds are thinner and you don't have to deal with any blizzards.''

The bottom line is that boarders are getting a later last chance to schuss, slalom and snowplow.

Four of the nine resorts in the San Gabriel and San Bernardino mountains remain open.

``It's been incredible,'' said Genevieve Paquet, spokeswoman for Snow Summit, which will close on Sunday after setting a resort record for the latest continuous operation. ``Spring skiing didn't kick in until the last two weeks of the season. We were reporting more winterlike conditions that anything else.''

To date, Snow Summit has received 164 inches of snowfall - most recently a dusting on Saturday - at its base; its average is 75 inches. The previous latest ending date of continuous operation was May 1, 1983, following the last major El Nino winter, when the resort was open 171 days. This season will have seen 157 skier days; the norm is 140.

And with 155 percent of average snowpack recorded by the Los Angeles Department of Water and Power in the Eastern Sierra, Mammoth Mountain isn't expected to shut down its chair lifts until July 4.

``It just gets to be a lot more fun,'' said Steve Keef, an avid skier and chief hydrographer for the DWP in Bishop. ``You worry more about getting a sunburn than ruining your skis on rocks and other obstacles.''

Mammoth averages 353 inches of snow, but this season it has received a generous dumping of 490 inches. During the epic El Nino of 1982-83, when the facility closed its runs July 28, the mountain was smothered with 567 inches of white stuff.

But take heed: The longer resorts stay open, the more challenging the conditions.

Friday at Mammoth, I was expecting several inches of powder after witnessing with glee the previous evening's snow flurries. But upon targeting my first pitch of ``powder,'' I found instead a confusing mass of humbling snow - a thin, windblown crust atop an inch or two of light stuff above a frozen base. It was a spring smorgasbord - three separate, distinctive conditions in a single turn adding up to one sticky wicket. My boards would grab as if I was shredding in peanut butter, and soon I was reduced to skiing the groomed runs.

It was Mother Nature's fault and she really kicked my butt.

``The wind has packed the powder, leaving a thin crust layer on top and making the grains smaller and more dense,'' Schwabenton explained. ``It really catches edges and is hard to turn in.''

Comforting words, to be sure.

If anything defines spring skiing it is variation - vastly changing snow conditions. Throughout the day, the sun's rays soften the snow, creating a mushy mess by day's end. That melt is frozen overnight leaving early-bird skiers to deal with icy runs. The alternating of thawing and freezing produces large granules commonly known as corn snow.

The best cure is to arrive late and leave early, avoiding the extremes, for that midday middle ground can be awesome. Find a groomed run and head down.

At Mammoth I found solace on Solitude, a more difficult trail accessed by Chair 5 with terrain as smooth and even as a glassy day on Crowley Lake - seen shimmering to the east. Ah, nonstop runs of 1,300 vertical feet in about a minute.

So bring a T-shirt - as well as the thickest jacket you own - and enough ski waxes for a range of conditions, and hit the hill again before the fireworks of July.

What's left to carve

Where spring skiers and snowboaders can go, along with snow-base totals, anticipated closing dates and telephone numbers for updates:

Mount Baldy: 48 to 84 inches, mid-May, [phone].

New Mountain High: 24 to 36 inches, May 5, [phone].

Snow Valley: 48 to 95 inches, day-to-day, [phone].

Snow Summit: 12 to 36 inches, Sunday, [phone].

Mammoth Mountain: 168 to 192 inches, July 4, [phone].

CAPTION(S):

Photo, Box

PHOTO (Color) Spring skiing at Mammoth is anything but crowded. Lifts will run until July 4.

John McCoy/Daily News

BOX: What's left to carve (see text)