GOES-R IFR Probability describes regions where IFR Conditions are likely. For example, the IFR Probability field above, from 1400 UTC on 5 August 2016, shows high probabilities over part of the Piedmont from Virginia southwestward into Georgia. Observations confirm that IFR Conditions (and near-IFR conditions) exist in this region of higher probabilities.
The Aviation Weather Center maintains a website with products that dovetail nicely with IFR Probability fields. For example, the screenshot below shows stations reporting IFR Conditions (in red) and Low IFR Conditions (in magenta) ( a CWA-issued polygon on IFR conditions is included). The overall extent of the IFR Conditions in the image above and plotted below is also roughly similar. The G-AIRMET of IFR Conditions, bottom, also shows overlap with the IFR Probability field, as expected.