Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1129 AM EST Mon Jan 13 2020 Valid Jan 13/1200 UTC thru Jan 17/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Large Scale Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 36hrs then 00z ECMWF/UKMET/ECENS mean Confidence: Average Through about 48 hours, large scale troughing and closed upper low settles over interior western Canada with several impulses impacting portions of the Pacific Northwest to central Plains and Great Lakes regions. Beyond that time frame, a more significant shortwave trough moves across the Pacific NW and then extends throughout the west coast while a progressive shortwave tracks through the Northeast U.S. The south-central US to southeast U.S. is expected to be generally under zonal to ridging. The 12Z guidance has trended tighter with the evolution and progression of the polar vortex where the GFS now is not as fast/progressive ahead of the other models as previously seen. Though beyond 36-42 hours, it does shear out the energy faster across southern Canada and the Great Lakes regions. This puts the surface low track a step ahead of the rest of the guidance, though generally along the same track from the central Plains to eastern Great Lakes by 60 hours. As the upper low loses influence and moves east across the CONUS, a pattern changing shortwave amplifies over the Gulf of Alaska and Northeast Pacific Ocean. With a slower closed low (as well as north), the ECMWF pumps the downstream ridge across the Northwest and rapidly develops a closed low/deep surface cyclone along the Pacific NW coast into Vancouver on Day 3. While, the operational ECMWF/CMC are on the faster side, given the downstream influences, prefer the ECENS mean solution greatest though the operational 12Z GFS is further south/slower near the 12Z NAM. The evolution and spread is not terrible for the end of Day 3 for such an upstream wave through a relative data void that a non-NAM blend may work best weighted strongest to ECENS mean, then ECMWF/CMC/UKMET. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor