Judging from the lines at the checkout stations and the throngs of shoppers jamming the aisles of stores right up to closing time last night, Washington-area merchants are singing Jingle Bells in joyful harmony today.

Spurred by pent-up demand and pleasant weather, consumers came through, as expected, for retailers whose ho, ho, ho's weren't too full of cheer earlier this month when sales were less than spectacular. Somehow, that old bugaboo about warm weather hurting winter sales always goes by the board in the days immediately before Christmas.

Now that this year's edition of the annual spending orgy is over, consumers will awaken tomorrow to face the reality of overextended credit limits and the sobering thought of having to lower those heavy debt burdens. It's back to business as usual for merchants, meanwhile, although normal operations probably may have to be modified to handle all those returned gifts in the middle of after-Christmas sales.

It's business as usual, in fact, for most segments of the local economy. There are exceptions, of course, and the season to be jolly was anything but for some segments. If business as usual next year is a repeat of the past 12 months, those segments will have little to cheer about a year from now.

Two of them, in particular, can use a little cheer this time of year. May the days ahead be merrier for:

* The District's unemployed. There won't be enough new hotels and office buildings completed by next Christmas or the following one to reduce the city's jobless rate to an acceptable level. Even though the current 8.6 percent unemployment rate is relatively unchanged from the previous month, it is still more than twice that of Washington's suburban jurisdictions.

On the other hand, any one of 13 U.S. cities with higher jobless rates probably would settle for 8.6 percent. Gary, Ind., for example, has an incredibly high jobless rate of 20.2 percent. Cleveland is struggling with 13.6 percent unemployment, Newark, 10.7 percent, and Los Angeles, 9.8 percent. Still, 8.6 percent is serious, especially in the District, where jobs are being lost to the suburbs in a widening trend that began more than 15 years ago.

New jobs may not be added in time to make a difference next Christmas, but the urgency of the situation suggests that now is the time for the District to develop a more aggressive business attraction program along the lines of those in the more successful suburban jurisdictions. The glaring imbalance in the city's economy demands that business attraction immediately be made an economic development priority.

* Independent retailers and other small businesses in Washington's old downtown core, east of 15th Street NW. In any turf battle with the growing army of developers marching eastward, small business operators are odds-on favorites to lose unless an enlightened city government intervenes to assure the balance promised in the controversial Downtown Plan.

While the D.C. government has appointed a special task force of representatives from government agencies and small and large businesses to formulate an equitable downtown development policy, the process has been laborious. The wrecking ball tends to swing much faster than Washington's obligatory committee system usually works. Real estate deals, developers' obsession with a fairly unimaginative tenant mix, and rental rates (usually too high for small businesses to afford) still guide development downtown. Not surprisingly, market forces continue to drive out viable small businesses while committees deliberate.

J. Fernando Barrueta, executive vice president and director of leasing at Smithy Braedon Property Co., paints a rather bleak picture of what small business operators can expect by 1986. Writing in Smithy Braedon's bimonthly report on the Washington real estate market, Barrueta says an anticipated shortage of office space in the District in early 1986 and the rising cost of land will force rental rates upward. In the area east of 15th Street NW, he says, the price of land has risen to more than $800 a square foot, "which dictates rents of over $30 per square foot."

Few small businesses can absorb those rates, which are rising rapidly from the previous high of $18 to $20 a square foot. Only when the city stands behind its own downtown plan will the small business sector have a prayer of remaining a viable part of the District's so-called "living downtown."

May the spirit of common sense and sound economic planning prevail in favor of small businesses and the unemployed through the remainder of this year and the next.