Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 317 AM EDT Sat Jun 09 2018 Valid Jun 09/0000 UTC thru Jun 12/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation...with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ---06Z UPDATE--- No substantial change to the preferences outlined in the preliminary discussion. The main issue with model performance in the next few days will likely continue to be the fact that subtle shortwaves and convective-scale processes may be the dominant forcing in some areas given the overall lack of significant synoptic features in the eastern half of the CONUS. ---PREVIOUS DISCUSSION--- ...Broader model analysis for the Eastern CONUS... General Preference: 00Z GFS, 12Z ECMWF, GEFS+ECMWF Ensemble Means Overall Confidence: Average In general, the CONUS will see a significant split in the type of pattern over the next several days with dominant synoptic scale features in the West, and weak flow with limited synoptic scale forcing in the East. With the exception of the Northeast, 500mb heights east of 100W longitude will generally be within a 50 meter range. This means that convective-scale processes will be able to be the dominant forcing for some QPF placement, along with shortwaves embedded in the overall flow. This leads to more uncertainty with QPF, and the rest of the forecast as a result. However, models have moved into better agreement with the placement of a quasi-stationary front draped from the Midwest into the Ohio Valley and Mid Atlantic. Therefore, the overall forecast confidence is listed as average. For model preference in the eastern US, prefer to lean toward the GFS, ECMWF, and their respective ensemble means. The 12Z UKMET seems to amplify the flow pattern too much over the Ohio Valley and Mid Atlantic on Sunday Night and Monday; the 00Z NAM shows much stronger mid-upper level vorticity maxima (likely convectively influenced) in the same region, which substantially influences its forecast; and the 12Z CMC seems to be too far north with its placement of convection and the surface front from Saturday Night through Sunday. ...Significant trough pushing into the Northwest this weekend; lifting into southern Canada on Monday with more zonal flow... Preference: 12Z ECMWF, 12Z UKMET Confidence: Slightly above average The 00Z GFS appears to be exhibiting its usual fast bias with the lead shortwave kicking ENE with this trough as it reaches the Northern Plains, as well as the accompanying surface front. The 12Z ECMWF and UKMET appear to offer the best compromise for more likely timing of these significant features that will be driving much of the significant QPF in the region. The 00Z NAM and 12Z CMC show more differences with respect to the amplitude of the trough through the West, and placement and intensity of the developing cyclone in the vicinity of the Canadian Prairies. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Lamers