Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 135 AM EST Thu Nov 07 2019 Valid Nov 07/0000 UTC thru Nov 10/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... ...00Z Model Evaluation with Final Preferences and Confidence... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Shortwaves cutting into the Pacific Northwest Ridge... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM/00Z ECMWF blend Confidence: Slightly below average ...07Z update... The models continue to make run to run changes regarding eastern Pacific shortwaves into the existing ridge off of the Northwest Coast. The 00Z GFS remains an outlier with its cold frontal progression through the Great Plains Sunday morning with a non-GFS blend preferred. Across the Northwest, the 00Z ECMWF backed off on the intensity/position of a shortwave valid 00Z/10, west of British Columbia, which impacts the orientation of low-mid level flow into the Pacific Northwest. The 00Z ECMWF now more closely matches the 00Z NAM while the 00Z CMC/UKMET remain a bit more aggressive with the shortwave feature. The 00Z ECMWF and 00Z NAM represent a fair middle ground and will be preferred. ...previous discussion follows... Significant differences show up with the timing of shortwaves currently over the Pacific Ocean, as they track downstream into an anomalous ridge located just west of the North American coastline. The 00Z NAM/GFS are slower with one of these shortwaves reaching the southern coast of British Columbia on Friday compared to the 12Z ECMWF/UKMET/CMC. Meanwhile, amplification of troughing will occur across western Canada as the feature drops south toward the northern U.S. Saturday into Sunday. The 00Z GFS is sharper with this next wave with a more amplified ridge just offshore of the Pacific Northwest. The GFS solution is a near outlier when looking at the 570 dam line at 500 mb compared to ensemble spaghetti plots. While differences remain with the non GFS guidance, a 00Z NAM/12Z ECMWF blend is an acceptable compromise at this point. ...Remainder of overall pattern across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average ...07Z update... No significant changes were noted in the 00Z ECMWF/UKMET/CMC compared to their previous 12Z cycles to warrant any changes to the preference. ...previous discussion follows... The start of the short range period shows broad troughing along the eastern 2/3 of the northern U.S., preceded upstream by anomalous ridging over the eastern Pacific into the Pacific Northwest. By Saturday/Sunday, the flow is expected to flatten a bit although another shortwave should send another arctic front into the northern U.S. There is good agreement outside of the Pacific Northwest and central U.S./Canadian border through Sunday morning with a general model blend sufficing. A large cold front will sweep through the East Coast with a surface low along the front deepening near Nova Scotia Thursday night into Friday. Across the Southwest, some minor differences show up with a closed upper level low offshore southern California/northern Baja California. The 00Z NAM/GFS are closer to the coast whereas the 12Z ECMWF/UKMET/CMC are displaced farther from the coast. At this point, through Sunday morning, a general model blend will work here as well. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto