Usually the weather is reasonably predictable. The typical systems are big ones you can see coming across the pacific for quite some time. The forecasts & satellite imagery give a pretty good idea when and where will get the worst of it, but aren't great as far as what the local effects will be (which can be quite dramatic given your objectives).
Of course the weather can come up sooner and change more quickly up high than the general forecasts indicate, but if you've done your basic homework it is unlikely you will be surprised by a freak storm.
As long as you are willing to modify plans based on weather you should be able to salvage a good time even with a less than wonderful forecast.
