Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 246 AM EDT Mon Jun 29 2020 Valid Jun 29/0000 UTC thru Jul 02/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Closed low anchored over New England ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average An upper-level low initially over southern Quebec is forecast to reach central New England by Monday and then become anchored in place through the middle of the week as it becomes cut off from the main northern stream flow. The 00Z NAM tends to drop more energy farther south compared to the global models which overall are fairly well clustered through the period. Will prefer a non-NAM blend as a result. Deep upper trough/closed low across the Intermountain West ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS/UKMET/ECMWF Confidence: Slightly above average A strong mid-upper level low currently over the Pacific Northwest is forecast to continue amplifying across the northern Rockies and Intermountain West through Tuesday morning as an upper-level ridge builds across the Midwest and Great Lakes region. Thereafter, the core of the upper low should be refocus farther north over southwest Canada going through Wednesday and Thursday. This will yield a quasi omega-block pattern across the north-central U.S. through the middle of the week. The 00Z NAM is overall a bit stronger than the global models which it has been tending to advertise over the last couple of days. The 00Z CMC though is again slower to lift the energy north out of the Intermountain West, and as it eventually does so, it ends up shifting stronger height falls farther east with greater impacts across the northern High Plains compared to the other models. Will again prefer the better agreement/clustering of the 00Z GFS, 00Z UKMET and 00Z ECMWF solutions with this system. MCV/Weak mid-level low over MN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS/UKMET/ECMWF Confidence: Average A strong MCV and associated weak mid-level low center currently over MN is expected to lift north through western Ontario over the next couple of days. Overall, the 00Z CMC appears to be too slow with the forward motion, and even the 00Z NAM lags the model consensus a tad by later Monday and Tuesday. A somewhat more progressive solution is expected based on the model trends over the last 12 to 24 hours and the latest satellite imagery. A blend of the 00Z GFS, 00Z UKMET and 00Z ECMWF will be preferred for the time being. Shortwave amplifying toward mid MS Valley by Monday night ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non_ECMWF blend...through 60 hours Blend of the 00Z GFS/UKMET...after 60 hours Confidence: Slightly below average The guidance supports a convectively enhanced shortwave or MCV lifting northeast across eastern TX and toward the mid MS Valley by Monday night. Overall, the 00Z ECMWF appears to be a bit too weak with the evolution of this system, but all of the models do support the energy crossing up through MO and IA going through Tuesday. However, there is significant model spread thereafter as the models disagree on whether the energy gets pulled north through the upper Midwest ahead of the deep upstream trough over the West, or if the system gets left behind and then potential drifts down to the southeast given the proximity of northwest flow around the west side of the trough over the East. The 00Z GFS and 00Z UKMET support the energy lifting north through the upper Midwest, but the 00Z NAM/CMC solutions suggest the energy gets left behind over IA and then begins to actually settle back down to the southeast while also gradually weakening. The 00Z ECMWF suggests the energy will tend to be ripped apart with some of the energy breaking away to the north and some of it dropping down to the southeast. A non-ECMWF blend will be preferred through about 60 hours, with a GFS/UKMET blend thereafter as the bulk of the 00Z GEFS and 12Z ECENS members favor the energy getting pulled northward by the upstream trough over the West. Confidence with this evolution though is certainly a bit limited. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison