Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1258 PM EDT Tue Jun 09 2020 Valid Jun 09/1200 UTC thru Jun 13/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Preliminary Model Evaluation Including Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Trough lifting through the Central Plains before absorbing into a closed low north of the Great Lakes... ...Occluded low lifting into the Great Lakes and cold front moving across the eastern CONUS through Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-CMC through Thursday Non-CMC and Non-NAM Friday Confidence: Average A closed low initially over the Central Plains will eject northeastward and open as it becomes absorbed into a longwave trough/closed low centered north of the Great Lakes Thursday morning. An occluded low pressure will lift northeast beneath this, with the accompanying cold front pushing east to be along or just off the Atlantic Coast Friday morning. The guidance is in reasonably good agreement with the evolution of these features despite a complex pattern, with only the CMC being outside the acceptable envelope as it is too weak and too slow with the progression of the weakening upper trough and surface cold front. Into Friday, the NAM becomes a strong outlier with the strength of the longwave trough that builds in behind the cold front, so despite being usable D1-D2, it is removed from the preferred blend by D3. ...Cristobal Remnants... ~~~~~~~~~~~~~~~~~~ Preference: General Model Blend Confidence: Above Average The 12Z NCEP and 00Z Non-NCEP guidance remains tightly clustered to the track as Cristobal accelerates N/NE into Canada by Wednesday night. Although the NAM becomes slower than the track and the consensus late D2, by this time any impacts from Cristobal should be well removed from the CONUS, and as such a general model blend is suggested. ...Closed low off British Columbia and associated longwave trough digging onshore the West Coast through Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: ECMWF/ECENS with light weight of the CMC/UKMET Confidence: Below Average Closed low off British Columbia is progged to spin nearly in place through Thursday before beginning a slow jog southeast towards the coast Friday. South of this feature, a longwave trough extending from the closed low will progress gradually eastward towards the West Coast, with an embedded shortwave approaching CA/OR D3. There is considerable spread, especially by D3, in the placement of this shortwave, likely due to a wide latitudinal spread in the position of the closed low at that time. The NCEP guidance is generally further south with the closed low off BC, and faster with the progression of the trough into CA, while the non-NCEP guidance is further north off BC and then slower with the progression of the trough. The GFS has been a fast outlier, and is even faster at 12Z, while the 12Z NAM has also sped up a bit from its previous iteration. Meanwhile the non-NCEP guidance has been gradually slowing, and seems to be more tightly clustered. An approach favoring the 00Z/ECENS seems best at this point, with some weight included of the other non-NCEP models, but confidence is below average due to spread and run-to-run inconsistency. Weiss Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml