SHOPPERS, SPORTS FANS and museum-goers should be pleased to know that one proposal scheduled for consideration at a meeting today of Metro's budget committee could provide weekend subway service by next September. The operative word is could, since there are alternative ideas and several stages of approval involved. Still, we think Metro should move ahead with additional service.

Cost and ridership forecasts for nine months of Saturday and Sunday operations, for eight hours each day, indicate that the service would be a worthwhile investment. To operate for the last nine months of Metro's fiscal year, which starts July 1, would add $1.8 million to a total bus and rail subsidy of nearly $100 million. That's less than 2 per cent - a small enough amount, considering the potential benefits, to justify at least a trial period.

Not only would the weekend subway hours be a boon to shoppers and stores, but moreover much of the weekend and congressional travel through Union Station and National Airport would benefit. We suspect, too, that many prospective visitors to the Smithsonian and Hirshhorn might ride the subway there rather than spend who knows [WORD ILLEGIBLE] long searching for a parking space. There is also the not-insignificant matter of Redskin crowds next year, not to mention the possibility that more subway service might encourage more events at D.C. Armory and RFK Stadium. And in warmer weather, weekend service to Arlington Cemetery presumably would attract tourists.

Others proposals include a suggestion that the Saturday schedule would be better if it were for longer than eight hours. There is support, too, for additional evening service during the week - until, say, 10 p.m. - which would accomodate more train and plane travelers.

Ridership estimates indicate that some 50,000 to 60,000 rides might be taken on a Saturday, and 25,000 to 30,000 on a given Sunday. The normal total on a weekday now is about 130,000, by next September, this figure could range from 175,000 to 200,000. Moreover, if weekend subway service were to spark new activities and store operations in the region on Saturdays and Sundays, results at the farebox might well improve the revenue picture. At this point, with additional stations scheduled to open in 1978, the time is right to try offering more convenient services. We therefore urge today's Metro committee session to approve a budget recommendation [WORD ILLEGIBLE] weekend service so that a smooth transition can take place by next September.