National Weather Service United States Department of Commerce

Strong Atmospheric River Bringing Heavy Rain to the Pacific Northwest; Areas of Snow in the North-Central and Eastern U.S.

A strong atmospheric river will bring prolonged heavy rainfall along with gusty winds to the Pacific Northwest through much of this week. The heavy rainfall may lead to widespread urban and river flooding. Accumulating snow is expected over parts of the central Appalachians and Mid-Atlantic today as well as the Upper Midwest and the Upper Great Lakes this evening into Tuesday. Read More >

The annual exceedance probability (AEP) provides a way of comparing rainfall to the climate of a particular area. For example, a certain amount of rain may be less rare in Louisiana than Missouri. Estimating the annual chance of observed or forecast rainfall amounts may provide a way of determining the significance of that rainfall for a particular location.