Wind patterns

Question
Windlover, a bit of a meteorology question if you happen to know much about it,
I have found that when i use online wind forecasts, when they say the wind will continue to blow or decrease slightly as the evening progresses; sometimes the wind decreases as forecasted (though usually it decreases more than forecasted) however sometimes it just continues to blow all evening through to the night - is there simple meteorolgical explanation for this? - or any way of figuring out if it will behave as forecasted?
Thank you as always, and sorry about the vagueness of this question..

Answer
Aaron,

As with any forecast, the weathermen are always 50% right and 50% wrong.

Wind forecasting is a bit more difficult than telling us if it will rain or shine. Some winds are created from fronts moving through and other winds are created by pressure gradients. The wind from fronts are from pressure gradients but some areas like here in the Gorge, pressure gradients are reliable due to heat rising in the east and cool air from the coast out west creating a difference in the Gorge and thus the consistent summer winds.

Where you are could be affected by pressure gradients similar to the Gorge. These type of winds are predictable but can be variable due to small changes in the gradients.

For example; If it cools down faster than expected, then the wind may die off sooner. If the heat stays up, then the winds may stay up into the night. Some nights in the Gorge the wind blows all night long (which is really peaceful when camping as the wind in the trees is like white noise. It also means that sailing will start early the next day :).

So, if you have any way to determine the pressure gradients in the area you are sailing in, you may be able to track them and learn to determine if the wind will stay up or drop. The forecasters are using these to determine wind if they know that it is not being caused by a front.

Hope this helps.
Keep on sailing,
Windlover