November is the wettest month of them all in western Washington

Out of all the months in the year, November is typically the wettest of them all in western Washington. Coincidentally, November is also the number one month for river flooding, primarily since there is usually little mountain snowpack to soak up those warmer rainy days when snow levels rise.

Western Washington could use a wet November. This year has been abnormally dry. October finished with a deficit of about one inch of rain at Sea-Tac Airport, with Olympia over one-and-a-half inches below average, and Bellingham just over a half-inch of rain in the hole. October made it the eighth month drier than average this year — April and September were the only months wetter than usual.

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Many parts of western Washington are between four and eight inches behind average rainfall this year. The dry weather during the end of October did not help.

However, this month looks like it will retain its wettest-of-the-year image. A big change in the dry weather pattern that finished October will result in a parade of wet Pacific weather systems to provide much-needed rainfall into next week.

Total precipitation forecasts into the weekend of Nov. 11 show over 10 inches of rain falling in the Olympics, and rainfall totals for the western interior along the Interstate 5 corridor from Bellingham to Centralia are expected to range from two to six inches.

Sea-Tac Airport measured a bit under three inches of rain in October, so the next week or so of rain should exceed last month’s total rainfall. Sea-Tac usually averages a little over six-and-a-half inches of rain for November.

Most area rivers are running well below average. This series of wet weather systems should raise river levels, but for now, no significant flooding is anticipated except in the Skokomish River in Mason County.

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With the airflow coming off the Pacific Ocean, temperatures are expected to remain relatively mild, with highs generally in the 50s and lows in the 40s. Snow levels in the mountains above pass levels will also be moderately high.

Each of these incoming weather systems is expected to kick up some wind as well, not excessive wind, but enough to bring down many leaves off trees. Combined with rain runoff, storm drains could get clogged with leaves, producing water ponding on roadways. Everyone should do their best to keep local storm drains clear of leaves.

Many western Washington residents do not use umbrellas, but this may be a period of soggy weather where an umbrella may be handy.

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