The four-day Thursday holiday weekend, which began with drizzle and gloom, ended on a day of clear skies and bright sunshine that eased the way for thousands of travelers returning home to face jobs, school and December.

After recording a high temperature of 57 degrees yesterday, seven degrees above normal, forecasters said they expected to start the year's last month today on an even warmer note, with highs in the 60s.

At the Baltimore Harbor tunnel, a major highway link between Washington and the cities of the Northeast, southbound auto traffic was reported heavy throughout the day. A backup of from 3 1/2 to 4 miles was reported last night. Trafic on many other arteries was said to be heavy also, but flowing smoothly.

Rail passenger traffic in the northeast corridor between Washington and Boston was described by an Amtrak official as the heaviest of the year. Although Amtrak ran 26 extra trains yesterday and hooked extra cars to the 66 trains regularly scheduled to run in the corridor, more than 9,000 passengers were forced to stand, the official said.

Traffic at National Airport also was described as extremely heavy in terms of both passengers and of vehicles arriving to pick them up and drop them off. "This evening is probably as busy as we've been in the past year," an airport official said.

Good weather minimized delays, the official said.