For the best localized weather reports and forecasts, check https://pocasimeteo.cz/ -- unfortunately only available on Android and possibly unavailable in some countries.

The application not only offers a reliable forecast but also real-time measurements. These are very important because each local spot has its best wind direction. If you launch at our place, it may well pay off to observe the situation at the best oriented spots and sail there.  Check Radslav for NW-SW, Dolní Vltavice for SE, Černá for NW-NE.