Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 147 PM EST Thu Feb 07 2019 Valid Feb 07/1200 UTC thru Feb 11/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Eastern U.S... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average There is above average model agreement across the eastern U.S. with respect to the deep upper trough/closed low and cold front sweeping east across the Great Lakes, Ohio Valley, Tennessee Valley and Eastern Seaboard going through Friday. Cold high pressure will arrive in the wake of this system through the weekend. A general model blend will be preferred. ...Central/Western U.S... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS and 00Z ECMWF Confidence: Average A pair of closed mid/upper level lows will drop through the western U.S. during the forecast period. The first, currently near 44N/135W, will drop southeast toward the central California coast before weakening and opening up into a progressive shortwave trough across the Intermountain West going through Saturday. There is good agreement among the models with the evolution of this system through this period. However, by Sunday as the energy quickly ejects east across the central Plains and toward the OH Valley, the 12Z NAM ends up hanging on to a somewhat stronger shortwave impulse that is also a bit more progressive than the well-clustered global models. Stronger ensemble support per the GEFS and ECENS suites lies with the non-NAM camp of solutions. Meanwhile, a much stronger closed low is expected to form across British Columbia Friday night which then drops south across Vancouver Island and just offshore western WA early Saturday. Thereafter, the closed low should broaden a bit and shift southeastward and inland across the Pacific Northwest through Sunday as additional shortwave energy digs south down across British Columbia. The guidance has come into good agreement with the details of this closed low as it pivots inland, although the 12Z NAM tends to be a tad stronger than the multi-model consensus and is also a slower than all of the global models. By the end of the period though, the 12Z non-NCEP models per the UKMET, CMC and ECMWF have all trended and converged toward the idea of a third closed low feature evolving over southwest British Columbia and Vancouver Island as shortwave energy digs underneath a developing ridge axis over the Yukon and adjacent Northwest Territories of Canada. The 12Z NAM is completely out of phase by comparison and has any secondary height falls displaced well off to the northeast closer to Alberta. The 12Z GFS does have energy digging south across southwest British Columbia, but it is notably less amplified. The latest GEFS mean and ECENS mean do not support the more aggressive non-NCEP camp for the time being, and as such, the model preference will continue to be the 12Z GFS and 00Z ECMWF since the prior ECMWF run does have this better ensemble support. However, given the latest trends. confidence is somewhat reduced. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison