Hello Claude, indeed, we are subject to a strong northeasterly flow between an anticyclone over Scotland and a depression over the Gulf of Genoa. The pressure gradient is quite tight, which partly explains why it sometimes blows up to 45-50 km/h, reinforcing the feeling of cold.
Also, the wind blows stronger during the day than at night and this is explained. During the day, the higher sun heats the ground which communicates its heat a little higher. Pressures drop on the ground under the updraft and there is a void to fill. This results in strong downdrafts causing the gusts which drop in the evening and at night since the sun is no longer there to heat the lower layers.
And on the rest of the country?
In the morning, we will have a clear sky and therefore a radiant weather, under a pure blue sky struggling to raise the mercury, still very low. Attention, a small limit might lick Flanders in the morning with more clouds up to a line ”Tournai-Ghent” with a sleet on the coast, quite isolated however. Around noon, we will gently return to the positive under shelter with 0 to 4°C, but under a fairly strong north-easterly breeze.
In the followingnoon, the sun will once more push back these clouds at sea, the coastal strip will also find clearings while the sun will dominate elsewhere (apart from a few cumulus clouds over the Ardennes). Under these conditions, the mercury will fetch 1 to 6°C under a still strong northeast wind reaching 35-40 km/h in gusts. As soon as the sun sets, the cold will set in once more everywhere.
