The warm, drizzly weather Tri-Citians have experienced during the past couple of days isn't merely unseasonal -- it actually set a record.
Wednesday's high temperature of 58 degrees at the Tri-Cities Airport in Pasco bested the previous record of 56 degrees set in 1998, said forecaster Rachel Trimarco of the National Weather Service.
Like this year, 1998 was a La Niña year, marked by above-average temperatures and precipitation, according to the National Oceanic and Atmospheric Association.
La Niña is a weather phenomenon defined by the NOAA as "cooler than normal sea-surface temperatures in the central and eastern tropical Pacific ocean that impact global weather patterns."
In the Pacific Northwest, weather conditions are likely to be wetter and warmer than usual in the late fall and early winter during a La Niña year, and colder than usual later in the winter.
The National Weather Service's Climate Prediction Center expects weak or moderate La Niña conditions to continue through the winter of 2011-12.
But at least in the short term, Tri-City temperatures are expected to drop back closer to normal in coming days.
Temperatures typically average in the upper 30s or lower 40s during late December, and it's likely the Tri-Cities will drop back closer to that range by New Year.
Trimarco said a cold front was expected to move in Wednesday night that would slowly cool temperatures in the Mid-Columbia.
Today's high likely will be in the low 50s and Friday's in the low 50s. The temperature should be in the mid-40s by Saturday, she said.
Rain is likely to continue today and could be mixed with some light snow Friday night as temperatures cool.
The region also could experience winds of 10 to 20 mph, although a wind advisory on the National Weather Service website is more likely to affect central Oregon, Trimarco said.
The wind advisory prompted the Washington State Department of Transportation to restrict movement of mobile homes along Interstate 82 from Prosser to the Oregon state line on Wednesday.