Resources

Regardless of where you are going in the Coast Mountains, always do your research, learn the required skills, go in a group, leave a trip plan and emergency response plan with a reliable contact, and follow backcountry ethics. Below are some resources that I use to plan my trips.

Weather

The main resource I use for weather forecasts in the Coast Mountains is SpotWX.

SpotWX allows you to drop a pin on the map, then see different weather models for that area. I usually look at the top few and form an average of what they are saying. Pay more attention to the lower resolution models. 

Other mountain weather forecasts: 
Mountain Forecast
Whistler Blackcomb Forecast

Wildfire Smoke Forecast

Trip Beta

There are a few places I look to for information about mountains, trails, access, etc.
Bivouac has a ton of information about first ascents, different routes, general mountain information. There's a paid version which includes trip reports, photos, and more. 
South Coast Alpine Climbing, South Coast Touring, and Club Tread are good community resources for recent conditions, trip reports, access updates.

Maps

I use Gaia on my cell phone. Some blogs and forums have GPX tracks which you can download and import into Gaia. The website is also a great planning tool which I use to draw tracks to use out in the field. 

There are other apps, too, and the government topo maps are good to have as a backup.

I use Google Earth a lot to get a sense of terrain and to plan routes. While it's hard to get an accurate sense of the steepness of terrain, it is great to get a general sense of what you will be dealing with, where snow sticks around, where boulder fields are, rivers, FSRs, etc.

Road Conditions

The community sites mentioned above area great place for this. There are also a number of BC 4x4 Facebook groups and forums with even more info. The BC government website also has information about closures and the conditions of certain FSRs

Safety

Adventure Smart has lots of great information about how to stay safe in the hills. Avalanche Canada is active usually from December to April, providing avalanche forecasts, weather reports, recent snowpack and avalanche reports. 
I use a Garmin InReach for emergency satellite communication, or to check in when I don't have cell reception. A monthly/yearly subscription is required. 
Make sure you take a wilderness first aid course including CPR! There are 20, 40 and 80 hour versions. I would recommend the 40 and 80 hour courses. Canada West Mountain School offer these courses through the summer, usually in North Vancouver. There are other companies, too.

Preservation

Always follow the Leave No Trace principles when in the hills. Take the time to learn about wildlife safety, how to avoid a wildlife encounter and what to do if it happens. In the Coast Mountains, you are almost always in grizzly, black bear and cougar territory. In certain areas you'll find wolves, moose, wolverines, etc. Respect that this is their home and you are passing through.
Find out what you can do to help protect BCs parks and wilderness.

Outdoor Clubs

There are 3 main outdoor clubs active in the South Coast: BCMC, ACC and VOC. These are great ways to meet other outdoor enthusiasts and learn about the local mountains. They also have a number of mountain huts which can be reserved through the clubs.
There are other smaller clubs and meetup groups.