The faculty and staff of Westbrook Elementary in Bethesda are skeptical. Local meteorologists are doubtful. In fact, everyone who has heard the tale of the helium balloon that was launched from the school grounds last spring and landed some 3,000 miles west in Oregon is baffled.

The mystery is heightened by the fact that, with the prevailing westerly wind patterns, the balloon must have sailed clear around the world, according to WDVM-TV (Channel 9) weatherman Gordon Barnes, who said the balloon would have travelled from 15,000 to 20,000 miles in its journey over the Atlantic Ocean, Europe, Russia, Siberia and finally, the Pacific Ocean.

It all began two weeks ago when the school received the card that was attached to the balloon when it was sent off in the annual launch on May 1, 1981. Handwritten on the card was the name Jefferson, Ore., 97352, a small town 15 miles south of Salem. The postmark was Salem, Ore. There was no name and no other message.

School Principal James Connor said he contacted Barnes, who told him that no currents exist in the jetstream to carry a balloon from east to west across the United States.

"The probability is one in 10 million," that the balloon sailed around the world, Barnes said, but added, "it's not impossible. Anything's possible."

Another meteorologist, Doug Wingeard of WJLA-TV (Channel 7), suggested the balloon could have travelled some 6,000 miles in a northeasterly direction taking it over the North Pole and down the Canadian coast. The over-the-pole route is "possible although it seems unlikely to me," said Wingeard.

Since the annual launchings began 13 years ago, all the pupils, from kindergarten through sixth grade, launch as many of the colored balloons as their allowances will buy (they sell for three for $1, with profits going to the PTA). Last year 310 students participated, each sending off one or more balloons in hopes one would travel the farthest. The winner receives free tickets to the school's spring carnival.

"It was fun," said Elizabeth Miller, the 7-year-old who launched the balloon that brought the postcard from Oregon. But even she had doubts.

"I was amazed when I heard," said Elizabeth, who recently transferred to Wyngate Elementary in Bethesda.

In the past, said school secretary Pat Ramsey, "we've received postcards from New Hampshire, Vermont and the Chesapeake Bay area. We never expected one from Oregon."

Why it took so long for someone to send the card back is a mystery. Ramsey said that, generally, "responses start coming in after three days, most of them from the Eastern Shore. After about a month they start tapering off."

Before the balloons are launched, a weather-resistant tagboard with a hole punched in the corner is tied to the balloon, explaining the launch and asking the finder to put her or his name, address and stamp on the pre-addressed card and drop it in the mailbox.

Explaining why it is unlikely the simply constructed helium balloon could have made the round-the-world trek, Stuart Brown, a national weather meteorologist at Intercon Weather Consultants in Camp Springs, said that while gaining altitude, a balloon of this type "would expand because of the rarefied (less pressure) altitude. Eventually it would burst."

"Going around the world, it would really have to hold up," said weekend weatherman Paul Anthony of Channel 9. "After a day the things fizzle out--they loose their oomph."

If it did not fly through the air, how did the balloon, or the card, end up in Jefferson, Ore.? "Maybe it hooked onto a train or something," suggests Ramsey.

"I would suspect by means of foul play," said Brown. "It could have been found by someone and carried to Oregon."

Connor, who won't write it off as a hoax just yet, said he is trying to find a laboratory to examine the soil and mineral smudges on the card. As of yet, no one is interested in pursuing the matter.

But even with a complete soil analysis, nothing can substantiate that the balloon actually sailed around the world. "It just can't be proven," Barnes said.

Last Friday, Westbrook held this year's annual launch. In the meantime, the mystery of the helium balloon remains unsolved.