NOAA's second-generation Global Ensemble Forecast System (GEFS) reforecast dataset is utilized to create a model climatology of cloud ceiling height and visibility at the Core-30 airports across the United States. These values are further used to create calibrated probabilistic predictions of IMC. GEFS Reforecast 2 data for December 1984 through May 2015 are stripped to the location of each Core-30 airport for the first 30 forecast hours. Cloud ceiling height and visibility are subsequently parameterized from the temperature, pressure, and specific humidity fields. These derived values are calibrated and validated with hourly surface (METAR) observations at each location. Combined, these steps provide an initial assessment of the suitability of reforecast data for aviation applications and specifically cloud ceiling heights and visibility. Results from this validation study are applicable to continued ensemble development and recommendations for post-processing the Next Generation Global Prediction System (NGGPS).