First the bad news. According to the weather man, there is almost no chance of snow for the Washington area on or before Christmas.

As for the good news, there is none. It may well rain on Christmas Day, the U.S. Weather service says-a freezing rain if it starts early, or just a plain old garden variety rain if its starts later.

Winter, which began at 12:21 a.m. today, will be ushered in with partly cloudy skies and temperatures in the 40s between today and Monday. But a low pressure area expected to form over Alabama is to blame for the prospect of rain by Christmas.

While on the subject of celestial matters, here are a few other items of interest.

The moon will occult Venus on Dec. 26 at 6:16 a.m. EST in the WASHINGTON area. An occultation is similar to, but technically different from, and eclipse.

Venus, visible in the lower easttern sky, will reappear at 7:29 a.m., about 30 degrees above the horizon. The entire event, according to Mihran Miranian, an astronomer at the U.S. Naval Observatory, will be visible to the naked eye (assuming that skies are clear) but binoculars or a telescope will improve the view.

Finally, for the seventh straight year, the Official Timekeepers for the World are adding a leap second to the day on Dec. 31. Because of atmospheric drag and other factors, the earth's orbit around the sun has been slowing at the rate of about one second a year. Insertion of the extra second - between 23:59:59 (Greenwich Mean Time) of Dec. 31 and 00:00:00 Jan. 1 - will bring clocks into line with the earth's passage.