Wet weather will usher in the new year

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A series of wet weather systems are expected to wrap up an uncharacteristically dry December in Clark County, according to the National Weather Service.

Rain was forecast to begin late Monday. said Rodger Nelson, a meteorologist with the weather service in Portland. It will continue for the next six days, along with warmer temperatures, Nelson said.

“We’ll have rain pretty much through New Year’s Day, with short dry periods in between,” Nelson said.

About an inch of rain is expected to fall during the course of the seven days, he said. Temperatures are anticipated to climb to the lower 40s at night and daytime highs will be in the mid- to high 40s, he said.

“We are finally getting into our winter weather pattern,” he said.

Tuesday has a 100 percent chance of rain, a projected low of 44 degrees and high of 45 degrees, according to the weather service.

A ridge of high pressure in the skies above the region has pushed wet weather to the north and south during the month. That high pressure has now moved to the east, enabling rainy systems to migrate in, Nelson said.

Despite the rainy conclusion to 2011, December could still attain the distinction of the driest on record in the Portland metro area, Nelson said.

“We’ll have to wait and see,” he said.

As of early Monday, Vancouver’s Pearson Field has had a third of an inch of rain this month, 5.16 inches less than the December average, he said. The average rainfall for December is 5.46 inches.

“It’s pretty hard to catch up in six days,” he said.

The year 1876, when there was 0.88 inches of rain, currently is the driest December on record, said Steve Pierce, a Clark County weather expert and president of the Oregon Chapter of the American Meteorological Society. So far, with a third of an inch, this December beats that, but that will likely change, Pierce said.

“Odds are against us staying the driest after the next five to six days,” Pierce said.

Historically, a dry December is a harbinger for a wet January, he said.

“When you look back at the driest Decembers, 80 to 90 percent of the time there was wetter weather the following month,” he said. “There is a lot of winter weather to come.”

Paris Achen: 360-735-4551; http://www.twitter.com/Col_Trends; http://www.facebook.com/ColTrends; paris.achen@columbian.com.