Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1123 PM EST Sat Dec 01 2018 Valid Dec 02/0000 UTC thru Dec 05/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-CMC Blend Confidence: Slightly above average Model height forecasts show very limited spread through Monday (approx 36-48 hr forecast), with excellent agreement overall. Therefore, the first couple days of the forecast are higher confidence, and the model preference is for a broad-based model blend. This will account for any minor detail differences between the various models. The spread begins to increase in two primary locations by Tuesday: the West Coast with an approaching trough and a downstream shortwave ridge, and in the base of a broad, deamplifying trough in the Eastern US. The 12Z CMC was the only deterministic model near the outer periphery of model spread in some instances, generally with a flatter trough in the East, and an eastward displacement of the trough axis on the West Coast relative to most other models. Therefore, the CMC was excluded from the preference. Otherwise, although the spread increases, the different deterministic models are supported by at least some ensemble members, suggesting they are all reasonable possibilities. Therefore, a non-CMC blend is the primary model preference. The only other noteworthy difference is that the 00Z NAM maintains a narrow band of very heavy rainfall on Monday and Monday Night in the Southeast, and the NAM position is generally north of the other deterministic models and ensemble means. Less weight was placed on the NAM in this region given a lack of other supporting models. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Lamers