Late afternoon rain. It's damp and cold in the street. Inside it's mannered.

The two-month-long cultural celebration called "Japan Today" opened unofficially yesterday with a reception at the Phillips Collection attended by museum patrons and representatives of the Japanese delegation.

Three Japanese artists, Kenzo Okada, Toko Shinoda and Waichi Tsutaka, are each represented by 12 of their works in the show, which will tour the United States for one year.

The paintings were selected because they are individualistic yet combine traditional Japanese expression with modern Western abstraction.

As such they would seem a perfect introduction to the Japan Today program, which was designed to heighten American understanding of Japan through a celecbration of its arts and culture.

"We came up with ideas for this show that were in accord woth the manifestation of a national celebration," said Robin Cafritz, one of the Phillips curators. He began to elaborate, but interrupted himself. "Actually, there's no point in making a translation. It's good art and does not need translation or explanation."

The communication was not so direct, however, when the mannered art patrons met with the mannerly Japanese art forms. The East/West twain became an upstairs/downstairs gap that wasn't quite bridged by the green-carpeted stairway that led from the first floor bar to the paintings on the second level.

Downstairs, there was a party going on.

Upstairs, artists Okada and Shinoda talked quietly of their work with the handful of people who paused and asked questions in the serene gallery spaces.

The first floor conversation touched on the Japanese only peripherally, if at all.

From the crush came threads of conversation.

"I thought the editorial today on Jerry Brown was really funny. . . ."

One man passed along privileged information on a sure-to-win long-shot in the Middleburg races.

Another talked of how the Mob was now involved in the health food business.

Later, some of the downstairs crowd pushed up the stairs and jostled in the halls, muffling their tones briefly as they hesitated in front of a piece that particularly pleased. The first Okada, perhaps.

Muted, pastel oil. Chalky gentle, softly pale. He calls it autumn.

Many complimented the show in accents that bespoke years of practice.

They passed through the halls to the rooms beyond, making their own notations.

"The best is farthest. The only Lady is all the way to the back."

"Wouldn't you know it?" was the smooth response, as the art patron glided along the corridor to the room that held Toko Shinoda's sumi paintings.

Bold rushing of black. Shot through with gray-green color. Holding in skyspace.

Downstairs, still later, one would hear: "There have been similar shows celebrating other countries. This is Japan's year. They have a new embassy, a new ambassador . . . and we're pushing it." The celebration will include performing arts, film series panel discussions, courses and symposia.

Evening rain by now. First "Japan Today" event . . . Opens on Tuesday. CAPTION: Picture, At the reception, from left: Japanese Ambassador Fumihiko Togo, Mrs. Okada, Kenzo Okada and Mrs. Togo; by Harry Naltchayan-The Washington Post