Forecasters with the National Weather Service (NWS) Seattle office say confidence is high that an atmospheric river will turn toward western Washington late this weekend and remain into early next week. This will bring periods of heavy rains in both the mountains and lowlands.
The wet air mass is expected deliver 1 to 4 inches of rain in the lowlands during the 48-hour period ending 4pm Monday and 4 to 9 inches in the Cascades.
This amount of rain on top of 1/2-inch to 3/4-inch rainfall totals expected during each 24-hour period Friday and Saturday could lead to river flooding as well as urban and/or small stream flooding.
The current Nooksack River level forecast for the Ferndale area says to expect the river level to begin rising mid-day Sunday, January 28th, from below the 4-foot mark and cresting just short of the 18-foot mark during the early morning hours Tuesday.
Confidence is not as high regarding details such as location, timing and exact amount of the heaviest rainfall forecasters say.