Some really nerdy weather sites.
The Forest Service, National Park Service, state parks, and other land agencies maintain a network of Remote Automatic Weather Stations scattered around the country, in remote backcountry areas not covered by regular NWS weather stations in large cities. Used for fire danger and planning purposes. The data from these stations are gathered hourly and available on the internet.
Click on the state, and zoom in to where you want to boondock to see the near real time weather real close to where you intend to camp. Comparing the weather readings to a nearby NWS station will let you fine-tune the regular NWS forecast to your campsite.
Another weather site that lets you zoom in to a specific site is here:
This one is a little finicky and may have to click several times on a particular spot. This site uses an algorithm to estimate the weather at a particular spot, adjusting the area general forecast for altitude and other factors.
For a free on-line reference, sort of a Mountain Weather for Dummies, go here:
www.nwcg.gov
Here is a cloud chart, some tips on guessing the weather later today or tomorrow.