Previous posts discussed low cloud and fog detection at night using the GOES-16 Nighttime Microphsyics RGB (see here). That post in particular highlights a low cloud case in a warm air mass. In such a situation (warm regimes), the lowest clouds will appear aqua/blue. However, in a cold air mass the lowest clouds instead appear yellow to light green. This is because, while the red and green components remain similar in both temperature regimes, the the low clouds will have less of a blue component in the cold regime (cooler air mass so cooler in the 10.35 um channel).
Analyzing the Nighttime Microphysics RGB across southern Colorado on 13 January 2018, fog, as confirmed in webcams and in METAR observations, appears as a light green to almost yellow (Fig 1).
Figure 1: 13 January 2018 GOES-16 Nighttime Microphysics RGB over southeast Colorado. Full res
The 5-min RGB imagery captures the fog as it develops and evolves quickly across southern Colorado (Fig 2). The fog and low clouds appear a light green, while high thin clouds in the western part of the scene are black, and high thick clouds in the eastern part of the scene appear red. Towards the end of the loop, low clouds dissipate in El Paso County, but continue to fill in across the Arkansas River Valley. The RGB imagery was utilized by forecasters at WFO Pueblo to monitor the precise evolution of the fog and low clouds, especially in the vicinity of the PUB and COS TAF sites.
Figure 2: 13 January 2018 GOES-16 5-min Nighttime Microphysics RGB over southeast Colorado. Full res
-Bill Line, NWS
Satellite Liaison Blog 
