Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1149 PM EST Sun Nov 24 2019 Valid Nov 25/0000 UTC thru Nov 28/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Shortwave along Northern Tier with associated area of low pressure Mon-Tue... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average Current GOES WV imagery shows shortwave energy dropping into the northern U.S. Rockies late this evening. The latest model guidance continues to tighten with the evolution over the next 2-3 days as this wave skirts the U.S. border. An area of low pressure is forecast to race across northern MN and across Lake Superior Monday before shearing out into Quebec. Model guidance agreement is high enough across the board that a general model blend is reasonable with above average forecast confidence. ...Lead shortwave in developing global-scale trof in Four Corners by 00z Tuesday... ...Development of strong/broad surface low in Plains Tuesday and Great Lakes by Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non-CMC blend Confidence: Average Pattern changing shortwave/jet speed max over-topping the Central Pacific Ridge is expected to dive southeast into the Great Basin by 25.18z. In the weak, broad cyclonic flow, this wave starts to buckle through the Central Rockies and start to spin up a broad surface cyclone across the Central High Plains Monday into Tuesday. Overall in the last couple of model cycles, most of the deterministic guidance has come into better agreement with overall less spread seen for the day 2/3 forecast. The initial exception is the 12Z CMC which is considerably slower (and weaker) with the trough axis moving through the central Plains Tuesday/Tuesday night and its associated surface low too far to the south at it reaches the Upper Midwest. Otherwise, there is fairly good agreement with the ECMWF/GFS and their respective ensemble means. The UKMET is usable, but has some of a southward bias compared to the ECMWF/GFS/NAM. Overall, given the increased confidence, will lean on a non-CMC blend for this cycle. ...Strong secondary shortwave supporting with very deep surface low near N CA Tues, expanding across northern CA/N Great Basin by 00z Thurs... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average A stronger, secondary closed low approaches the northern CA / southern OR coast Tues-Wed and then slows/stalls, becoming a large, well-developed trough over the western U.S. by late in the week. A compact, strong low pressure will push into the coast with fairly good consensus of a sub-980 low reaching the coast. In the last 24 hours, the model guidance has tightened considerably, with a slight northward jog with the overall track of the system. There is now fairly good clustering with the most recent deterministic guidance and in the latest ensemble guidance. After landfall, the upper low, broadens and slides south. The greatest agreement exists with the 00z GFS/12z ECMWF but the 00z NAM and 12z UKMET are solid enough in the ensemble suite to have good agreement to incorporate into a preferred blend. While there is good alignment of the wave development to provide confidence, its current location/source and influences of the Ridge and northern stream still provide some reduced absolute certainty to this blend. So, while the confidence has improved substantially since yesterday, it is still average. A blend of the available deterministic guidance is preferred at this time. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor