Tillamook County Emergency Management Advisory: Flood Watch until 04:00PM Tuesday

December 1, 2023; 5:30 am

* WHAT…Flooding caused by excessive rainfall is possible.

* WHERE…Portions of northwest Oregon, including the following areas, Cascade Foothills in Lane County, Central Coast Range of Western Oregon, Central Oregon Coast, Central Willamette Valley, Coast Range of Northwest Oregon, Greater Portland Metro Area, Lower Columbia, North Oregon Coast, Northern Oregon Cascade Foothills and South Willamette Valley and southwest Washington, including the following areas, Greater Vancouver Area, I-5 Corridor in Cowlitz County, South Washington Cascade Foothills, South Washington Coast and Willapa Hills.

* WHEN…Through Tuesday afternoon.

* IMPACTS…Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. Creeks and streams may rise out of their banks. Flooding may occur in poor drainage and urban areas.

* ADDITIONAL DETAILS… – A series of atmospheric rivers will bring periods of widespread heavy rain through early next week. Cascade snow accumulations through Saturday morning will experience heavy rain Saturday night into Sunday morning which will contribute to excessive run off. Total rain amounts for the entire weekend range between 3.0-5.0 inches along the coast, 4.5-6.5 inches over the Willapa Hills and Oregon Coast Range, and 3-4 inches across the interior lowlands, with 4.0-7.0 inches of rain expected over the Cascades, Cascade foothills, and western Columbia River Gorge. 2.5-3.5 inches of rain is expected for central Columbia River Gorge and Upper Hood River Valley. Localized heavy rain will lead to higher rain totals. – http://www.weather.gov/safety/flood

* AFFECTED AREAS: NORTH OREGON COAST … CENTRAL OREGON COAST … COAST RANGE OF NORTHWEST OREGON … CENTRAL COAST RANGE OF WESTERN OREGON … LOWER COLUMBIA … GREATER PORTLAND METRO AREA … CENTRAL WILLAMETTE VALLEY … SOUTH WILLAMETTE VALLEY … NORTHERN OREGON CASCADE FOOTHILLS … CASCADE FOOTHILLS IN LANE COUNTY … WILLAPA HILLS … SOUTH WASHINGTON COAST … LOWER COLUMBIA AND I – 5 CORRIDOR IN COWLITZ COUNTY … GREATER VANCOUVER AREA … SOUTH WASHINGTON CASCADE FOOTHILLS

Instructions:  You should monitor later forecasts and be alert for possible Flood Warnings. Those living in areas prone to flooding should be prepared to take action should flooding develop. Given the aforementioned rainfall amounts expected this weekend, river levels will be rising quickly. Most rivers have anywhere from a 30-50% chance of reaching at least minor flood stage, except the mainstem Columbia and Willamette Rivers which is less than 10% chance. Coastal rivers however have a 40-60% chance of reaching minor flood stage and 20-30% chance for reaching major.