Atmospheric river moving into Pacific Northwest

An atmospheric river is taking aim at the Pacific Northwest and is expected to bring more rainfall to Thurston County before moving out of the region.

The National Weather Service (NWS) Office in Seattle forecast calls for a 100 percent chance of precipitation on Thursday, March 12, with new rainfall amounts between one-tenth inch and one-quarter inch possible. The daytime high should be near 41 degrees with a southwest wind of 11 to 13 miles per hour (mph) and gusts as high as 22 mph.

There is also a 100 percent chance of precipitation on Thursday evening with a chance of rain possibly mixed with snow. The overnight low should be around 34 degrees with a southwest wind of 6 mph.

“An already active, wet pattern across the Pacific Northwest in the Northern Rockies is not only expected to continue but intensify the next few days as another (Pacific system/atmospheric river) moves into the region,” said the NWS Weather Prediction Center in College Park, Maryland, in a short range forecast on Wednesday, March 11.

“Very heavy snow is expected for higher elevations of the Olympics/Cascades and northern Rockies, with totals of multiple feet forecast. Gusty winds are also expected throughout the region, prompting (blizzard warnings) for the Cascades and Olympics.”

The outlook for Friday, March 13, calls for a 90 percent chance of precipitation. The daytime high should be near 42 degrees with a light south wind. Rain and snow are likely after 11 p.m. on Friday with an overnight low around 31 degrees.

The threat of flooding is also possible for Thurston, Lewis and Grays Harbor counties through the end of the week.

“Periods of heavy rain beginning Wednesday and continuing into Saturday (March 14) will cause rivers in Thurston, Lewis and Grays Harbor (counties) to rise. Some rivers could reach flood stage as early as Thursday,” said the NWS Office in Seattle in a hydrologic outlook issued on Tuesday, March 10.

“Rivers of the most concern are the Chehalis from Grand Mound to Grays Harbor, the Newaukum and the Skookumchuck near Bucoda. Rivers will crest … late this week into the weekend.”

There is also a chance of showers through the weekend with the odds for heavier rain picking up on Sunday evening, March 15. Rain is also likely at the beginning of next week in Thurston County. Forecasts are subject to change.