Here's my rule of thumb:

TV weather: Should I wear more layers?

Wunderground, The Weather Channel sites/apps: What's on the RADAR?

For wind predictions, start with an app such as WindAlert (they've acquired a bunch of others). The quality of the forecasts from these apps varies by location, however, so check around with locals or just monitor a few for a while.

For the best forecasts, there are subscription services. These are definitely location sensitive, especially for a place with complex features (land/water/prevailing flows).

Most times, a combination of the first three is sufficient. When running important regattas in Newport, decisions on where to race (ocean vs bay) or whether (and how long) to postpone ashore can make the paid services invaluable.

Hope this helps.

Mike