Daytime fog over snow in Wyoming on 21 November 2018

By Ed Szoke and Dan Bikos

On 21 November 2018, here is the GOES-16 visible (0.64 micron) imagery:

Visible loop:
click here or on the image for the animation

Do you see any fog in this imagery?

How about in this product, do you see any fog?

click here or on the image for the animation

This is the experimental CIRA Snow/Cloud Layers product. The purpose of the product is to distinguish clouds from snow cover on the ground during the daytime hours. In the product, low/water clouds generally appear as yellow or possibly greenish (as in this case) while high/ice clouds appear as magenta. Snow on the ground will appear white. This product uses a number of GOES-16 ABI bands (0.47, 0.64, 1.37, 1.6, 2.24, and 10.3 microns) as a RGB product with additional calculations. Note in our loop over central Wyoming we see a region that is green/brown in color over the white snow field that is decreasing in areal extent over time, indicating low cloud or fog. This product is currently on the RAMMB SLIDER page, however will be experimentally available on AWIPS via LDM from CIRA.

A product that is currently available in AWIPS is the Day Cloud Phase Distinction RGB which is shown here:

click here or on the image for the animation

in this product, snow on the ground appears green while low cloud or fog will appears lavender to cyan in color during the daytime. The reason is that we have relatively large contribution from the blue component with liquid cloud, small contribution from red component and large contribution from green component since it’s reflective in the visible band. The combination contributes to the lavender color for the low cloud / fog.

For this case, the METAR site at Riverton, WY reported fog as seen in this METAR plot at 1600 UTC:

A list of the observations from Riverton during the morning are shown here:

KRIW 211853Z AUTO 00000KT 6SM BR CLR M07/M09 A3016 RMK AO2 SLP279 I1001 T10721089
KRIW 211753Z AUTO 00000KT 6SM BR SCT002 M09/M10 A3018 RMK AO2 SLP291 I6001 T10941100 11094 21161 58001 $
KRIW 211727Z AUTO 00000KT 5SM BR FEW002 M11/M11 A3018 RMK AO2 T11061106 $
KRIW 211717Z AUTO 19004KT 4SM BR BKN002 M11/M11 A3019 RMK AO2 T11061111 $
KRIW 211707Z AUTO 00000KT 9SM SCT002 M10/M11 A3018 RMK AO2 T11001106 $
KRIW 211653Z AUTO 00000KT 8SM BKN001 M11/M11 A3019 RMK AO2 SLP293 I1001 T11061111 $
KRIW 211639Z AUTO 00000KT 3SM BR OVC001 M11/M12 A3019 RMK AO2 T11061122 $
KRIW 211633Z AUTO 00000KT 1SM BR OVC001 M11/M12 A3019 RMK AO2 T11111122 $
KRIW 211553Z AUTO 03003KT 1/4SM FZFG VV001 M13/M15 A3019 RMK AO2 SLP303 T11331150 $
KRIW 211543Z AUTO 00000KT 1/4SM FZFG VV001 M13/M14 A3019 RMK AO2 T11331144 $

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