A late winter storm dumped another four inches of snow on the Washington area yesterday, bringing the year's total so far to 19 inches, the largest annual accumulation since 1967.

The storm, spawned in the southern Rockies three days ago, hit the area before dawn, icing roads, trying up morning rush hour traffic in spots, closing schools and delaying air travel.

The ninth snowfall of the year, it strengthened the already growing suspicion of many winterweary residents that the last two months here have been meteorologically insane.

Insane, perhaps, but no records have been set.

The 19-inch snowfall total so far is only four inches greater than the long-time average for the area and is nowhere near the record falls of some bygone years such as 1899, when 49.8 inches fell, and 1966, when 44.3 inches fell.

So far this year, January totaled 10.3 inches, almost double the 5.9-inch average for the years 1888 to 1959, the period the Weather Services uses for weather comparisons. But February had only 3.8 inches, compared to the long-time average of 5.5 inches. The long-time average for March is 3.6 inches. The official total so far this March, measured at the National Weather Service observation station at National Airport, is 4.9 inches. Of that total, 4.1 inches fell yesterday and the rest on Wednesday.

What has made this winter seem so remarkable, weather service forecasters say, is not the total snowfall, but the fact that it has come in a series of steady but relatively small accumulations. Snow has been left on the ground in shaded areas almost continuously since early January.

"Usually, we get a couple of big storms, maybe 10 or 12 inches at a time, and then it melts right away," said one forecaster at National Airport yesterday. "This year, we haven't had anything bigger than four or five inches, but the cooler-than-normal temperatures have kept it on the ground."

Yesterday's snow may not be the last of winter. Forecasters warned of possible "precipitation" early next week, but said it is too early to say whether it will be rain or snow.

The 19-inch snow total so far this year is greater than any year since 1967, when 34.2 inches were recorded. Most winters in the 11 year since then have been warmer and drier than normal, heightening the contrast of this winter's snowiness.

Yesterday's storm forced all public schools in the Washington are to close - the fourth time this year for suburban schools and the third for the District of Columbia.

Morning rush hour traffic was tied up by icy slush and minor accidents, especially in suburban Virginia where salt supplies for clearing roads were reported to be running low.

National Airport closed from 10:50 a.m. to 12:22 p.m., causing flight delays while crews cleared snow from the runways. Dulles International Airport remained open throughout the day.

A spot check of federal government agencies indicated slightly above normal absenteeism by employes. However, many workers made an extra effort to get to work, leaving their homes earlier than usual and spreading the push hour over a longer but less congested period.

Yesterday's storm left a new blanket of snow throughout Virginia and Maryland with accumulations ranging from six inches on Maryland's Eastern Shire to 10 inches in parts of extremes southwest Virginia.

In Lexington, Va., 175 miles southwest of Washington, the City Council adopted a resolution Thursday night noting its frustration with the long winter. The resoluation directed Mayor Charles F. Phillips Jr. to "communicate in an appropriate manner to the proper authority the City Council's wish that the dastardly, inclement weather desist forthwith."

Asked if he had carried out the Council's wish, Phillips said in a telephone interview yesterday, "Due to the terrible weather, I have been unable to make contact with the proper authority, and I don't expect to until April 1," when the weather presumably will improve.