Ice Fog developed over Kansas City during the early morning hours of 18 January 2017, with accidents that snarled traffic (tweeted image courtesy @DrWxologist Chad Gravelle) starting before sunrise and continuing through the morning rush hour (Screenshot of News link from here). Dense Fog Advisories were issued. The animation above, of GOES-R IFR Probability fields, shows the slow westward progression of the Fog/Low Clouds into the Kansas City Metro area shortly after 4 AM CST. High IFR Probabilities persist through 1800 UTC and diminished shortly thereafter.
During this case, an absence of mid-level and high clouds allowed IFR Probabilities to reach very large values. The toggle below shows Brightness Temperature Difference fields (3.9 – 10.7) and GOES-R IFR Probabilities at 1115 UTC. Low clouds cover Missouri except for the region over the Missouri Bootheel. Note that the western edge of the satellite-detected low clouds is slightly to the east of the western edge of the IFR Probability in this case. Model data are suggesting that low-level saturation is occurring in those regions (over far southwest Iowa, for example) although satellite data were not yet showing a strong signal. Observations show IFR conditions (at Clarinda, Iowa, for example, where freezing fog is reported with 200-foot ceilings and 1/4-mile visibility).