GOES-16 Mid-level Water Vapor (6.9 µm, top). Low-level Water Vapor (7.3 µm, middle) and Clean Window Infrared (10.3 µm, bottom) images from 0001-1801 UTC on 19th January [click to play MP4 animation]

Thermal signatures of the still-unfrozen water of Lake Oahe reservoir (along the Missouri River, in central South Dakota) were evident in GOES-16 (GOES-East) Infrared, Low-level Water Vapor and Mid-level Water Vapor images on 19th January 2025 (above). As a result of cold arctic air (morning low temperatures across western/central SD were generally in the -10 to -20F range) flowing across the open water of Lake Oahe, there were also 2 brief periods of light lake effect snow at Pierre (KPIR), each which reduced the surface visibility to 2.5 miles (below).

Plot of surface observation data from Pierre, South Dakota from 1100-1700 UTC on 19th January [click to enlarge]

With a cold/dry arctic air mass in place over the region, the GOES-16 Mid-level Water Vapor (Band 09) and Low-level Water Vapor (Band 10) weighting functions peaked at lower than normal altitudes (below) — with significant amounts of radiation from the surface reaching the satellite detectors (thereby enabling a signature of Lake Oahe in the Water Vapor imagery).

Plot of Weighting Functions for GOES-16 Water Vapor Bands 09 (cyan) and 10 (brown), calculated using 1200 UTC rawinsonde data from Rapid City, South Dakota on 19th January [click to enlarge]

Plot of rawinsonde data from Rapid City at 1200 UTC on 19th January [click to enlarge]

In fact, the Total Precipitable Water value derived from 1200 UTC Rapid City rawinsonde data (0.03 in) (above) was a record low value for 1200 UTC soundings on 19 January (below).

Rapid City rawinsonde climatology of Total Precipitable Water for all 1200 UTC soundings on 19th January [click to enlarge]

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