One night after a widespread dense fog event, we have been monitoring more fog formation very closely. Unlike the previous night, the visibility has not fallen quite so far, so fast at most of the airports across the Tennessee Valley; just a few sites in typically fog-prone valleys are reporting visibility of less than 1 mile. However, coverage is the question, and the default 11-3.9 micron satellite imagery was not particularly helpful in diagnosing that. There are hints of fog in the valleys of northeastern Alabama, but it’s tough to be sure how widespread the fog might be.
The Nighttime Microphysics RGB imagery was much, much more useful–and confirmed what the surface observations were telling us. The 0802 UTC pass indicated that much of the fog is confined to the river valleys in and around the Huntsville CWFA, especially in the northeast Alabama valleys and the Elk River around the Tennessee-Alabama border (near where the mouse pointer is located). Furthermore, the fainter gray-cyan colors surrounding the Tennessee River (bisecting the CWA) supported some of the less-dense fog reports coming from airports such as Muscle Shoals (KMSL) and Huntsville (KHSV).
This imagery helped confirm the surface observations, and helped with the decision to avoid a widespread dense fog advisory–at least temporarily.