GOES-East Day-Snow-Fog RGB imagery played an important role in operational decision-making at NWS Norman, OK (OUN) when forecasting fog and low stratus progression on 03 Jan 2021. Making this situation particularly difficult was the presence of snow cover beneath the thin low cloud/fog deck, as cloud features could not be easily discerned in visible satellite imagery alone. From OUN, “Since the area of fog/stratus was so thin, you could see the snowpack through the deck, making it even more difficult to discern on visible satellite. The RGB allowed the liquid cloud to “pop out” so we could see the development and dissipation trends.”
The forecaster on shift mentioned that the GOES-East RGB imagery influenced operational decision-making related to TAFs as well as the temperature forecast. Specifically, “Use of the Day Snow-Fog RGB was critical in my forecast for the KOKC TAF, along with hourly temperatures west of OKC. While we did have a TEMPO group of IFR conditions at KOKC for a couple of hours due to uncertainty and potential impact, the dense fog and stratus dissipated on the western and northern edge of the OKC runway complex. The high res models forecasted this area to persist through the afternoon across the OKC metro to the KOUN terminal area, but with the aid of the RGB trends, we were confident that it would not make it past the western parts of OKC.”
First, GOES-East 0.64 um imagery reveals, to an extent, low clouds evolving atop snow cover (Fig 1). Given the similar appearance between the low cloud cover and snow cover and semi-transparency of the cloud cover, the precise location and edges of the cloud cover is difficult to discern throughout the evolution.
Now viewing the Day-Snow Fog RGB, the low clouds pop as shades of light blue against the background of red (snow cover) and green (bare ground), allowing for it’s precise location to be more easily tracked in space and time (Fig 2).
Similarly, Day Cloud Phase Distinction RGB imagery can be utilized to discern low clouds (light blue) over snow cover (green) and bare ground (darker blue) with more clarity than VIS alone (Fig 3).
Bill Line (NESDIS and CIRA), Kevin Brown (NWS/OUN), Randy Bowers (NWS/OUN)