THE HILLS ARE alive with the sound of skiing from the Piedmont to the Poconos.

"There is lots of snow, and that's our most precious commodity," said Cal Conniff, president of the National Ski Areas Association.

And evidently there are lots of skiers -- such as Rick Simpson, 28, a Fairfax County arson investigator who cools off on the slopes; he recently returned from one week at Sugarbush, immediately followed by seven days in Vail. "I was skiing in powder that was knee deep, the best snow I've ever seen."

Simpson's review seems insightful. "Most areas chalked up record attendance levels in December," said Conniff, whose organization represents the operators who handle 90 percent of the ski resort dollars spent in this country and Canada. On the eastern seaboard -- in this case "skiboard" -- it's a boom year.

In the off-season, 17 eastern ski resorts constructed new lifts. Nationwide, more than $40 million was invested in new snowmaking equipment and grooming machinery. To shorten lines and broaden smiles, Snowshoe, Big Boulder, Camelback, Jack Frost and Ski Liberty added new lifts. Seven Springs even built a roller rink.

Then, as if on cue, heavy snows fell, blanketing the New England and Piedmont regions. "Coast to coast, these are the best conditions we've had," boasted Conniff. The nation's ski resorts, buffetted the past two years by an ailing economy and winter droughts, has rebounded even though the cost of living -- and therfore the cost of playing -- is soaring.

In New England, Stowe, Mount Snow and Waterville Valley are celebrating the season. But northern climes are not alone; the slopes at southern resorts, such as Ski Roundtop and Massanutten, are brimming. On weekends, Snowshoe looks like rush-hour in the mixing bowl. At Wintergreen, the U.S. Ski Association is holding sanctioned competition for the first time in the South.

This brisk business is grand for those with reservations and a handful of cash on hand. But what of the relatively poor and those with poor plans? "Tell them to get on the bus," suggests Rob Freibaum, president of Sea and Ski, a Gaithersburg travel agency. His company is one of several that organizes group ski travel from Vail to Virginia.

For instance, Sea and Ski offers one and two-day trips to Wintergreen that include round-trip bus transportation and lift tickets -- no meals -- for $25. An overnight trip for six or more costs $60 per person; or two to a studio for $69 each.

"There is plenty of space up North and out West," said Freibaum. Air fare, lodging, lifts and transfers for a trip to Colorado, he said, range from $500 to $800. Three days of skiing at Sugarbush -- via bus -- is $175, including meals, lift tickets and double occupancy lodging. Ski Trips Unlimited offers seven nights at Jackson Hole, Wyo., March 6-13, including lift tickets, air fare and ground transportation, for $720.

There are approximately 30 ski resorts within a half-day's drive, or less, of Washington. And this year, Freibaum insists that budget-conscious skiers are staying close to home. Mid-week trips (they're cheaper and usually mean less congested slopes) are popular. In addition, some ski resorts such as Seven Springs and Snowshoe are often heavily booked by the weekend.

The key, according to Manyon Millican, vice president of marketing at Snowshoe, is to call ahead. "A lot of people are saying, 'Don't go to Snowshoe. It's booked.' But that's not necessarily true. Yes, mid-week is the better time to come. But we can usually find space on weekends."

This year, Snowshoe has a new lift, four new runs, a swimming pool and three new restaurants: Lodging capacity has increased by 1,200.

At Seven Springs, weekends are crowded as well. "They're terribly busy," said Roger Jones, president of Ski Trips Unlimited. But it helps to get on the weekend waiting list. "A lot of people have second thoughts by Thursday." For those who elect to drive, $75, double occupancy, buys two days and two nights, lifts, lessons, tax and swimming pool privileges. For groups of three or more, the price is $65.

Charles Wines, ski area manager for Massanutten Village, a three-hour drive from Washington, is luxuriating in this year's snow accumulation. A victim of last year's no fall when only 1 inch of snow graced his mountain, Wines is relishing the 1981-82's 2 feet of flakes. With day and night skiing, Wines touts brief "7- or 8-minute lift lines. It's going pretty good this year."

His optimism is shared in Pennsylvania where 42 ski areas fight for business. "So far it's going extremely well," said Bill Stenger, president of Pennsylvania Ski Operators and general manager of Jack Frost. "This is one of the rare years that come along when we get good natural snowfall and cool temperatures for snow making.

To Stenger, the sound of wind-blown snow falling on city streets is just as sweet as the downhill sweep of skis; he said that recurring snowstorms in the "marketplace" -- New York, Philadelphia, Baltimore and Washington -- provide skier incentive. "We have very, very strong bookings. Local hotels are doing the best they've ever done."

For weekday skiers, Jack Frost is a bargain for Pocono snow. Lift tickets are $11 -- $5 cheaper than many competitive sites.

If the second half of the season equals the first, resorts will gorge themselves on the profits of flume, providing a lift for one part of the sporting industry that flirted with disaster during the past two years. Which is to say that America's skiers will have had a season to remember.

Fish is a Washington writer and a fishing and skiing columnist for The Post's Weekend section.