Low clouds lingered over the upper midwest behind a departing low pressure system late on Wednesday the 19th. A strong signal was evident in the brightness temperature difference field from GOES-East, above, from 0200 UTC, extending northwest to southeast over eastern Minnesota into northern Indiana. Note, however, that ceilings in this region were indicative of mid-level stratus rather than fog. IFR Probabilities are correctly very small underneath this stratus.
An animation of the fields, above, shows the development of a low IFR conditions over western Minnesota. The brightness temperature difference fields also show their development, and the combination of satellite predictors and model predictors lead to very high IFR Probabilities in that region, both in the GOES-based fields, shown half-hourly, and in the MODIS-based fields, shown when available.
The near-full Moon provided ample illumination for the clouds, and the day/night band reveals the extensive cloud cover over the upper midwest, but as it only shows the top of the clouds, it is difficult to determine if visibility restrictions are also present. The Brightness temperature difference produce is also shown, which field is helpful in screening out snow cover and city lights.