Checking the weather for a short afternoon flight showed visibility of more than 10 sm and clear skies locally, with a barely moving front off to the west. The forecast showed nothing unusual, although clouds and limited visibility were expected to arrive with nightfall several hours after my anticipated landing time. The temperature/dew point spread was narrow, but around the Great Lakes, we often had high humidity content at lower altitudes as moisture blew in off the water. Seeing ground-level dewpoints only a few degrees away from temperatures wasn’t concerning. Overall, the weather looked great for a local sightseeing flight in the late afternoon.
As I took off, I recall noticing the front miles to the west had some significant high-altitude cloud buildup along its extent. This didn’t mean much to me at the time, other than thinking the slow-moving front was far away and that I had plenty of time left to fly. As we flew along, pointing out landmarks to my passenger, the ground started getting noticeably darker as the sun began to set behind that wall of clouds to the west. The clouds were so high that this “artificial sunset” happened hours before actual sunset. About 30 minutes into the flight, the air started to cool off and the visibility started to drop, slowly at first, but then quickly as the air cooled just enough to begin producing a cloud layer.
