FD Valid time and For-Use

[cloudclimber]

Hey guys, I have a question about the FD's. I want to know what "Valid" and "For use" mean. You know when it says Valid 090600 for example, but the column says "For use 05-09". What does that mean? For example, take a look at the FD's for STN YWK here -https://flightplanning.navcanada.ca/awws/html/doc/user-guide/anglais/weather-products-e.html

It's as if saying you can use it starting at 0500z, but it's valid starting at 0600z?

[J.O.]

The TC AIM says,

Data for the production of FD forecasts are derived from a variety of atmospheric data sources, including upper air sounding measurements of pressure, temperature, relative humidity and wind velocity, taken at 32 sites twice daily (at 0000Z and 1200Z). Following the computer run of a subsequent numeric weather model, FD forecasts are available at the valid times indicated in MET 3.1.

I can only assume that the “for use” time starts in advance of validity period time to allow for pre-flight planning. So you can flight plan with that report starting at 0500 but only for a flight occurring after 06:00.