Use to use it before finding swellmap, but I have no confidence in marineweather. Swellmap rarely gets it wrong.
Another good page is http://www.predictwind.com, but the the free trial is about to end and it is expensive to subscribe ($100+ a year), it is targeted towards sailers which probably explains the cost. But the info is good. I have been known to check Predictwind during a norwester at home, checked the signs and notice it is calm by 7pm, arrive to the sounds for perfect conditions Going to miss it.