The wind is onshore in France, but the terrain doesn’t have much of an elevation to cool the air as it rises upon hitting the coast.
Perhaps the reality is somewhat different to the graphic depiction, however I would consider the warm land having an effect on the air mass in contrast to the cooler sea.
I use a wx radar app almost every single day (flying, boating, motorcycling) and the reliability of the shown overcast and overcast with rain is often unreliable. It almost always rains when rain is shown but the qty is hugely variable regardless of the depiction. Cloud density is unreliable too.
The most reliable depiction seems to be sky clear.
If it shows a line of cloud arriving or departing I have found that to be ridiculously accurate at times.
Bodies of water between land masses obviously have an effect on weather. If you have crossed the channel more than once you will have noticed this.
I live on a peninsula between the Sea and a large estuary. Often the weather is different here than either over the sea, or over the mainland he other side of the estuary. The weather forecast often doesn’t take this into account either.
Coast effect has its roots in:
1. Lifting due to the terrain
2. Thickening boundary layer linked to mechanical turbulence
All the oncoming air has to go somewhere, and the only way is up. You can ride the updraft when flying along a coast and get a significant GS boost. Someone reported this on this forum when flying along the Bay of Biscay’s coastline with steady westerly wind. The wind veering due to lower Coriolis effect can also be measurable.
If the airmass is cold and close to saturation, for example after going above a body of water, it may not require a very large heaving to go across the edge and start producing precipitation. That’s why it always rains in Gothenburg.
I got a pic once showing the cloud following the French coastline perfectly.
What is interesting is that windy.com is correctly simulating this.
Land is cold in winter on the morning. If a moistured air mass is going over the land, its temperature will decrease and droplet will appear?…
In winter, sea water is higher than land (~13 C, vers ~5 for the land – check temperature at 7am).