Given that some coastal reporting areas cover hundreds of square miles and well over 50 miles in length, immediate vicinity accuracy can indeed be less than perfect. Buoy data for coastal cruising has been very helpful for us to assess interrelationships between waves and currents. Rain forecasting is immaterial, not so fog predictions.
There are spots that tend to have slightly more settled weather, especiallh depending on time of year and whether a el nino or la nina year.
But all in all, expecting forecasts to hold within 5 knots (for many with under 50 footers, 5 knots from 10 to 15 or 15 to 20 is huge) for more than 5 days or so is not all that common in my experience.....
...and for many years my job or hobby has had me looking at the weeks forecast.....while improved.....still iffy for that "weekly" forecast to be "right on"..... close, but sometimes close still changes your plans or comfort if you go.
The NOAA weather forecasting models are typically poorer in accuracy than their European and “private” weather models. The Canadian weather models are also poor. The reasons are complex and have been reviewed by Cliff Mass, below:
“U.S. Numerical Weather Is Still Behind and Not Catching Up: What is Wrong and How Can It Be Fixed?”