Forecasting for Belgium can be very tricky due to its proximity to the North Sea to the north and the Alps to the south, and southern Belgium has quite a varied terrain itself. The details of the weather conditions can vary greatly on a local scale, and I'm certainly not a local expert. Plus, the models are not in good agreement on the weather pattern. As a result, my confidence in this forecast is low.
The general pattern to start the event will be an upper level trough over the region, with a ridge of high pressure at the surface. The trough in the upper levels and a northerly wind at the surface will probably be enough to keep a good amount of cloud cover over the track on Thursday and Friday, but probably not enough to produce rain. This is where I'm uncertain - there's a very fine line between rain and no rain here, but I'm leaning the forecast toward no rain. The north wind will keep temperatures pretty chilly as well, with highs only in the mid to upper 50s F, or mid teens C.
The upper level trough will be exiting on Saturday ,and surface winds should shift to a more easterly direction. This should allow for more sunshine and warmer temperatures on race day. Of the three days, I'm most confident in Saturday being dry.
I expect this forecast will be changing through the week, and I plan to have the next update posted on Wednesday.