* WHAT...Increased threat of sneaker waves expected as a southerly swell impacts the coastline over the holiday weekend. * WHERE...Southwestern Humboldt and Coastal Mendocino Counties. * WHEN...From late Friday night through Monday evening. * 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. Don't be fooled by an ocean that looks calm. There can be 30 minutes of small waves before a sneaker wave strikes. Avoid rocks and jetties. Avoid steep beaches. Stay much farther back from the water and never turn your back on the ocean.