Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1142 AM EST Tue Mar 05 2019 Valid Mar 05/1200 UTC thru Mar 09/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Preference and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep trough over the Great Lakes/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Above average confidence and model agreement continues for the deep trough over the Great Lakes and Northeast US. The main trough axis will pivot through the region into Wednesday. A secondary shortwave trough will round the base quickly Wednesday night into Thursday. While there are some very subtle timing differences, placement in the mass fields are above average, with good agreement in the QPF fields. As such, a general model blend looks appropriate at this time. ...Deep closed low center near 32N 143W... ...Arriving across CA by Wed... ...Shearing downstream across the central Plains on Thurs... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 48 hours (7.12z) 00z ECMWF/UKMET/GFS blend after Confidence: Slightly above average Closed low currently centered near 35N, 133W will move northeastward toward the central California coast into Wednesday. In the big picture, model agreement is fairly good but looking at the details shows some timing and placement differences still. The GFS is a faster solution, bringing the open low onshore a few hours ahead of the NAM/ECMWF/UKMET. All of the guidance at least has similar placement. That wave then moves into the central Rockies where the model agreement actually improves and a general model blend is preferred. After 48 hours, another strong shortwave trough will approach the California coast. Here, model differences are more significant. The NAM is much stronger, closing off at 500 mb, while the ECMWF is more compact (but open) while the GFS is more open and faster compared to the rest of the guidance. Finally, the UKMET is on the slower side of the guidance, keeping the wave well offshore through 08.00z. For now, will suggest a general model blend early in the period (first 48 hours) then lean on a ECMWF/UKMET/GFS blend after. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor