Choosing a date: Do you want to ski in December or January? Low-elevation resorts in high latitudes -- Alaska, British Columbia and Montana -- are likely to get good early-season snow. High-elevation resorts in more southern latitudes get a scattering of early snow, too, but usually on north-facing slopes and in high-snow areas, as in Idaho, parts of Utah and along the Continental Divide in northern Colorado.

Do you like those late February and March weeks, when the days are sunnier and milder? Resorts in central and southern Colorado, northern New Mexico, Utah's Park City and California's Lake Tahoe get most of their snow from February on.

Once it falls, will the white stuff last? That depends on Mother Nature's moods, the jet stream, warming oceans, mid-winter heat waves and spring freezes. Go figure.

Fact finding: Check out the resort websites first, noting the "mountain facts." Then check independent ski and snow sports sites that collect and assemble resort data, including www.bestsnow.net, www.onthesnow.com and www.sportsamerica.com.

The most useful site is www.bestsnow.net. Authored by lifelong skier Tony Crocker, a former statistician, the site compiles facts you won't find elsewhere. The reports cover percentages of skiable powder days, the deviation from the average total snowfall, directional sun exposure as a percentage, and, most valuable, Crocker's personal observations.

ANNE Z. COOKE