* WHAT...A very long period westerly swell will increase the threat of sneaker waves.
* WHERE...Coastal Del Norte, Northern Coastal Humboldt, Southwestern Humboldt and Coastal Mendocino Counties.
* WHEN...From 4 AM PDT Sunday through Monday afternoon. .
* IMPACTS...Large, unexpected waves can sweep across the beach without warning, sweeping people into the sea from rocks, jetties, and beaches. These sneaker waves can also move large objects such as logs, crushing anyone caught underneath.