The weather today briefly turned dark and gloomy over the Augusta National Golf Club, but by the time the first shot is fired at the 50th Masters Thursday morning, the conditions are expected to be close to ideal.

Those gathered for the first major golf tournament of the season took advantage of the last full day of practice today. They did so after overnight thunderstorms rumbled through the area, drenching the 6,905-yard course. By midday the lingering sprinkles had stopped, to be replaced by low clouds and rising temperatures and humidity.

More pleasant weather is forecast and a little sunshine in his life is just what Ben Crenshaw, 34, hopes is on the horizon.

"I feel better these days than I have in a long time," said Crenshaw. "I feel I'm ready to make a run for it."

Crenshaw ended a long slump two Aprils ago by winning the Masters, closing with a 4-under 68. In 1985, Crenshaw won only $25,814 on the Tour.

Over the winter, however, he was treated for a thyroid condition and has recently regained some of his zeal for golf. "This place has a special mystique and it takes a lot of knowing," he said. "Experience certainly helps. You have to hit shots here that you don't hit anywhere else."

In other developments, U.S. Open champion Andy North, his right hand in a cast, withdrew from the tournament. North's withdrawal reduced to 88 the number of players expected to compete.

North said he has a bone chip in the right thumb, the result of an injury at his home in Madison, Wis., three weeks ago.

And Gary Player added a bit of controversy to the pre-tournament scene by saying no one should be surprised that non-American golfers are beginning to dominate the sport, and said the trend would continue until the PGA abandoned its all-exempt tour. (The PGA exempts the top 125 money-winners from the previous year from qualifying for tour events. Most other players must finish among the top 50 at the annual qualifying school.) "These are only my opinions," said Player. "But within 10 years I think the all-exempt tour will be gone."

The native of South Africa was the first non-American to win the Masters, taking the title in 1961, 1974 and 1978. Many foreign-born golfers have followed him to the United States and the European and Asian contingents have grown to a formidable degree.

Half of the last eight Masters winners have been non-Americans; the European team overwhelmed the Americans at last year's Ryder Cup matches, and, if North had not won the U.S. Open last year, it would have been won by either Dave Barr of Canada, Denis Watson of South Africa or T.C. Chen of Taiwan. "The all-exempt tour is breeding complacency," Player said. "I think there should be an exempt list of 60 players and the rest should qualify each week."