I saw a possible noctilucent cloud to the west that was shining through a break in the overcast overcast sky at twilight last night. It was not the typical wispy type, but more "even" in texture. After dismissing it, a friend who visited today and lives in an adjacent town saw it too. But he said it looked to him as though lightning was occurring within it. I told him (based on what I knew, which is not extensive, that I've not heard that actual lightning occurs in these clouds, but speculated that the effect could be from the setting sun's rays being filtered by other clouds in their path, causing quick changes in illumination of the 50 mile high noctilucent clouds. What, if anything, could have caused this "lightning effect"? Thanks.