GOES-R IFR Probabilities (upper left), 10.7 µm – 3.9 µm brightness temperature differences (upper right), 3.9 µm micron brightness temperature (lower left), 10.7 µm micron brightness temperature (lower right)

Stray light occasionally intrudes into the 3.9 µm channel, and that has a big impact on both the brightness temperature difference and therefore on the GOES-R IFR product.  The stray light impact on the 3.9 µm channel is evident at 0531UTC — it does not impact the 10.7 µm channel.  The big impact on the brightness temperature difference translates to a big signal in the GOES-R IFR probabilities.  Note how GOES-R IFR probabilities do not change underneath the high-level cirrus over eastern OK, southern MO and Arkansas:  GOES-R IFR probabilities do not use satellite data in regions of multiple cloud layers, or in regions of ice clouds.