NOW THAT THE Great You-Know-What of '79 is more slush than substance, the Monday morning quarterbacks are at full strength, ticking off their complaints about services that weren't provided during the storm. Fair enough -- for surely everyone has learned a little something about how to cope better next time. There are lessons of one kind or another for the police, and the snow-removal system -- and perhaps even for Marion Barry, who has put so much store in the role of a mayor as a delegator of power and a setter of tone.

We have no quarrel with the way authority was delegated, and nothing but praise for the hard work of those bus drivers, plow operators, police officers, sanitation crews and others who braved the storm to help clear up the mess. But the mayoral tone in an interview with Post reporter Milton Coleman from the back seat of a chauffered sedan was hardly calculated to lift the spirits of citizens who had been digging, slogging, skidding, slipping and falling -- or housebound and sneezing -- for several days. "What's to lead? It's not a crisis," he is quoted as saying; those with buried cars could take a bus. And when the buses weren't running? "They can walk."

Not since Marie Antoinette, you could almost say, but never mind. The big lesson from last Monday has to do with the Metro, whose fair-weather friends certainly had cause to inquire why one of the seven costliest wonders of the world -- the region's subway system -- couldn't move for three days. The first answer put forth, of course, was that nothing like this storm had ever happened before.

Baloney.Forget the charming-southern-clime fantasy that holds (against all evidence) that snow is a rare thing in these parts; that's precisely the mentality that brings chaos to the streets any time the town is hit by a "surprise" inch or two of the stuff. Face it: There is more snow here each winter than anybody seems ready to credit, even if this last load was huge. So rather than heap blame on Metro officials who were working with a relatively new system under terrible conditions, we prefer to suggest some changes for the next storm.

For one thing, the subway system should be treated as something indispensable -- no matter what it takes to get it moving, at least underground. That means parking the trains in the tunnel sections for all overnight closings when the forecast calls for measurable snow. It may even mean arranging overnight accommodations nearby for those out-of-town Metro operators who might otherwise be unable to make their way to work. That way, at least the underground network would be kept running. As for the outdoor tracks, there was some question, apparently, about whether Metro should spend between $22,000 and $100,000 for a heavy snow blower that it might not need all that often. The answer is yes -- for a system this important and this costly, the price of top equipment is relative peanuts.

As for the effort to dig out the above-ground tracks by hand, Metro got burned when it issued a public call for hired hands and then couldn't accommodate the response. It might be better next time to work with neighborhood organizations to round up assistance, or maybe to ask the Army engineers around town to mobilize their best troops and equipment for the job.

The better the transit system we build, the greater will be the dependence on it, and the more we will all expect from it. Expectations weren't met in last week's great storm. The widespread and surprised disappointment should be regarded by Metro officials as both a compliment of sorts and a directive not to let it happen again.