With snow predicted over the next few days, hope springs eternal in the minds and hearts of local snow aficionados. While we wait for the fluff, here's a primer on the stuff of our dreams.

Not all snow is created equal. The ideal snow is the kind welling up around your knees or even flying over your head as you make a sweeping turn down some untracked slope. But, one does not see such snow every day. Sometimes you are mired in what feels like mashed potatoes or skittering across bullet-proof ice. So what are the physical properties of epic snow?

Air temperature is a key factor in determining what kind of snow falls. Snow that drops through dry, cold air creates small, powdery flakes that don't lump together as they fall. Air temperatures of 0 to 10 degrees produce such snow — the "hero" stuff that makes everyone ski like a god. However, such snow is prone to drifting, which can be good and bad. It might blow entirely off of the previous snow surface and end up in the woods or on a lee slope, so depending on where you ski, conditions can be fabulous or sketchy. After a cold, windy storm, avoid exposed runs and head where the snow has been deposited by the wind. Wind-deposited snow can be light or compacted, so be cautious when making your first few turns.

It is a myth that it can only snow in temperatures below 32 degrees. It must be below freezing high in the atmosphere where ice crystals form to produce snow, but snow can fall through warmer layers to reach the ground. In fact, the heaviest snowfalls in the United States usually occur in temperatures of 32 degrees to 35 degrees.

If the temperature is warmer than 32 degrees, falling snow crystals melt around their edges and bond together, producing larger, heavier flakes and "wet snow." This is typical of coastal regions-think "Sierra Cement" or "Cascade Concrete" — or with warmer winter storms in inland regions. Wet snow stays where it falls, a plus, but can be difficult to ski through if very deep. Wet snow is ideal for making snowmen but not necessarily for snow sports. This is where fat skis and snowboards excel, as they allow you to "float" on the surface and not get bogged down.

Another useful indicator of snow quality and type is the snow to liquid ratio. This is the measurement of snow in its natural state measured in inches (or centimeters), versus its depth if melted. A 20-to-1 ratio is ideal-that is a snowfall measuring 20 inches in depth when melted produces 1 inch of water. This would be snow with 5 percent water content — the stuff of powdery dreams. Sierra Nevada or Cascade snow, while it comes in prodigious amounts — often measured in feet versus inches — can have a water content as high as 15 percent to 20 percent. The extra weight makes turning harder and tires you out quickly. And snow with a high water content can quickly become compressed and hardened into ice.

Ski Santa Fe reports a base of 18 inches but will be kicking off its season on Saturday. Open runs will be Midland, Easy Street and Pine Flats. All facilities and services will also be functioning.

Taos Ski Valley has a 24-inch base and is operating on a Thursday-Sunday basis until Dec. 15. Runs on both the frontside and backside are open.

Angel Fire will open on Dec. 15, and is reporting a 19-inch base. If offers the state's only night skiing, on 50 acres at the base of the mountain. A night ticket runs $24, or $12 with a same-day lift ticket. A season-long night pass costs $99. Another deal being offered again this year is its Weekday Flex Pass, which is good Sundays-Thursdays all season. It runs $189. Other news from Angle Fire is the new Nordic Center based out of the Angel Fire Country Club. It will provide 10 kilometers of groomed classic and skate-style trails, plus a snow shoeing lane, and a sledding hill.

Ski Apache has an 18-inch base and has 10 percent of its runs open — all clustered at the bottom of the mountain.

Sipapu has a 16-inch base and is open this weekend, as is Red River, which reports a 20-inch base.

Wolf Creek has a 37-inch mid-mountain base. It will host a College Day on Sunday, with lift tickets running $33 for students with a valid college photo ID.

Telluride reports a 23-inch base, but only a handful or runs are open. Dec. 14-17, it will host a World Cup/FIS team and individual snowboard cross competition, and an individual parallel giant slalom. The competition begins Dec. 14 with snowboard cross qualifying for men and women on Lower Misty Maiden, right above the Mountain Village. On Dec. 15, qualifying and finals go on for parallel giant slalom a bit farther up the hill on Upper Misty Maiden. Snowboard cross became an Olympic sport in 2006, after a decade-long run in the Winter X Games. Competitors run down a course that includes banked turns, terrain changes and jumps.

Silverton opens for the season on Saturday on a 40-inch base with either unguided or guided skiing. Runs expected to be open include Ropedeedope, Mandatory, Waterfall, Riff, Raff, Cabin, Colorado, Thread, String, Rope, Splitski, Half Track, Quarter Track, Delores, Bowling Alley, Tiger 1-5, Tiger Main and Concussion.

Copper Mountain has opened Colorado's only superpipe, with a 22-foot high trough. Most of the U.S. freeskiing and snowboarding half pipe teams have been training here, but it is open to anyone who wants to drop in. The resort hosts the U.S. Grand Prix comp Dec. 5-10.

Daniel Gibson can be reached at dbgibson@newmexico.com