My BoP has completed day one and Blue has launched an offensive toward Zadar (well actually across the whole front, but that's what it says). I fooled around with the weather a bit and now have gusty weather with restricted visibiilty, a little misty and cumulus with the tops around 10,000.
Check out this thread for some options to customize the weather in BMS.
https://www.bmsforum.org/forum/showthread.php?30320-Configuring-campaign-weather