Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 121 AM EST Mon Mar 04 2019 Valid Mar 04/0000 UTC thru Mar 07/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation Including Preference and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average 07z update: No significant changes in the 00z UKMET/CMC/ECMWF further support the initial thinking of general model blend. ---Prior Discussion--- Large scale model agreement continues to solidify especially with the vast global scale cyclone over the eastern half of the continent. Internal waves show similar depth and timing even as the vortex breaks down into Wed/early Thurs with some mild spread in eastern Canada with limited affects in the Northeast CONUS. The West there is more substantial spread especially by day 3, mainly in multiple stream mid-troposphere interactions/"Fujiwara". The main QPF driver is a southern stream shortwave emanating out of the Central Pacific today approaching CA late Tuesday into Wed. While there are some interaction with the closed low to the north (described below), it is minor allowing typical progression into CA, terrain and through the Intermountain West by late Wed/early Thursday. The 12z ECMWF is a shade further north with the inner core of the upper low, allowing increased interaction with the northern stream, breaking down the cyclone as a whole through the Intermountain West. By Thursday the GFS/CMC are a bit faster with the wave lifting into the Plains, but again this appears minor to support a general model blend here as well at slightly above average confidence. The greatest mass differences remain in the Pacific Northwest, where there is limited moisture to lead to only minor QPF differences Wed into Thurs. The closed low over S BC will dance with another compact wave out of the NE Gulf of AK late Tuesday, there has been growing consensus with this binary interaction with the GFS trending faster with the 18z run and maintaining at 00z. The NAM is the slowest, while the UKMET is fastest. The main difference by Wed is the EC/CMC trending west (favoring the northern vort center) while the GFS/UKMET press height-falls a bit east in WA, which in turn slides QPF a bit east. A compromise between camps appears appropriate and in line with overall ensemble mass trends. Further model spread occurs as initially the GFS, followed by the NAM break down the Gulf of AK ridge and blast strong shortwave height-falls SE stretching the upper low over SW BC into a SW-NE elongation into the Pacific. There is limited support for this magnitude/timing of breaking down the ridge even with GEFS ensemble members (as well as ECENS/CMCE members). So would be favoring something closer to UKMET/CMC/ECMWF blend for this area with a more concentric closed low. This is still upstream of the CONUS and blends into preferences by WPC medium-range forecasts (please refer PMDEPD). Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina