Washington — The storm that roared through the mountain west this week like a runaway semitrailer may be an example of weather soon to come. The region between the Rocky and the Sierra Nevada Mountains can expect a colder than normal winter this year, says the Commerce Department's National Oceanic and Atmospheric Administration. The East Coast, on the other hand, may be in for a relatively mild winter, according to the NOAA's just-released annual winter forecast.
''The months of December through February also are expected to be rather wet nationally,'' says Dr. Donald Gilman, chief of predictions at NOAA's National Weather Service.
Mother Nature has already visited the Cascade Mountains of Washington and Oregon with 16 inches of snow and 90-mile-per-hour winds, which brought blizzard conditions to the area on Tuesday. In northern California winds were so strong they blew over a large truck on a bridge.
As ''when it rains it pours,'' Dr. Gilman of the NOAA predicts the area stretching from inland Oregon, down the spine of the Rockies, to New Mexico and Arizona has a 55 to 60 percent chance of winter weather that is colder than normal. The Pacific coast, though, is predicted to have an even chance of a normal December through February.
The East Coast, which in many areas is still basking in an extended Indian summer (Washington, D.C., weather was close to shirt-sleeve Wednesday), has a 65 percent chance of continuing with warmer-than-normal weather, Gilman says. The Mideast, from the Mississippi Valley to the Appalachians, has a 60 percent chance of relatively mild temperatures.
The heart of the country, from North Dakota and Minnesota down through Texas, is predicted to have a normal winter.
Almost all of the US, with the exception of the Southern and Western coasts, is thought to stand a 55 to 60 percent chance of being pelted with an above-average amount of precipitation.
The southern tip of Florida, which already gets more than its fair share of sun during winter, is the only part of the country predicted to be drier than normal.
The pattern Gilman predicts for the winter of 1984-85 resembles those that were typical between 1930 and the early 1950s, he says. The most recent winter similar to the one he is expecting occurred in 1974-75.
NOAA's annual winter forecast is valuable for groups from local governments (which use it to plan snow removal budgets) to construction companies (who need it to set building schedules).
Dr. Gilman, however, makes not pretense of infallibility.
Indeed, last winter's forecast, which predicted milder-than-normal weather on both coasts, was somewhat off.
The last two weeks of December 1983 brought Arctic cold to these areas, killing citrus crops and fooling the NOAA.
The winter before that, however, 1982-83, was called more correctly. It was unusually mild in the East, as Dr. Gilman predicted - although the Old Farmer's Almanac had warned of ''incredible cold'' during those months.
Weather prediction is a ''somewhat soft'' science, according to Gilman.