Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1117 PM EST Sun Jan 12 2020 Valid Jan 13/0000 UTC thru Jan 16/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Large Scale Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 36hrs then 18z GEFS and 12z ECMWF/ECENS mean Exception: Non-NAM blend for Pacific Northwest end of Day 3 Confidence: Average The well advertised large scale trof has finally taken shape with the cold Arctic anchoring over the BC/Albertan Rockies in the next day or so. Multiple fast moving low amplitude shortwave parade across the Northern US Rockies into the Plains and then the Great Lakes. The guidance has come into solid agreement with the first two, Monday into Great Lakes and second broader but less defined NW-SE trof through the Northern Plains into Great Lakes, though as this system lines through the Upper Lakes, the NAM is a bit greater amplified as it can typically get by this period in its cycle. The 00z GFS while just a bit north/stronger than the UKMET/CMC/ECMWF, it has some of the flavor of the NAM without going all in by 60hrs as it comes back to the ensemble suite across the Northeast. By this time, the 00z GFS has been continually persistent in weakening the closed low and shifting it east, this is generally a problem also noted with the subtropical high and return Gulf stream flow across the South and so the GFS is less favored after this time in favor of the GEFS solution which is much more in line with the ECMWF/ECENS solutions. So the third Pacific shortwave that crosses into the Lower Northern Plains by early Wed and eventually develops a weak surface wave through the Ohio Valley, the GFS is much to fast, though the CMC is much too fast too and strong which is uncharacteristic of that guidance, so a preference toward the ECMWF/ECENS/GEFS is preferred with lower confidence after 60hrs east of the Rockies and with the remaining Arctic closed low that starts shearing into the northern stream flow Wed. As the upper low loses influence, 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 is on the faster side of its own ensemble suite, given the downstream influences, prefer the ECENS mean solution greatest though the operational 00z GFS are further south/slower near the CMC and UKMET. 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 Gallina