I take exception to characterizing “poor aerial reconnaissance” as partially responsible for the “surprise of the German offensive. The air corps compiled numerous reports regarding rail and road traffic into the region that could only lead to the conclusion of a serious build up of forces and material pending a major effort. Headquarters made a decision to let the operation proceed.
I understood that U Boats in the Atlantic radioed information that would predict meteorological conditions in the areas of northern France and Belgium. They knew when that area would have dense fog, and planned the attack timing accordingly.
So the “poor aerial reconnaissance” reference may be about the fact that conditions were overcast (heavily) making such reconnaissance “poor.” Though your comment points to reconnaissance over a longer duration.