There is option in sf to switch it off. Where is the fixer taking visibility range from? Fsx or active sky next? The reason I ask I see clouds drawing far away, below the visibility range.

That's probably ASN injecting weather and unrelated to d10sf I often see it with ASN.

 

The setting in dx10sf doesn't draw clouds which are 2x visibility range as set by weather engine. So if visibility is 10 miles dx10sf doesn't draw clouds 20 miles away as they would be indistinguishable from the fogged sky.

 

Turn it off I doubt you will see any visual difference, it just saves GPU effort on sgssaa.