Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 236 AM EDT Tue Jun 16 2020 Valid Jun 16/0000 UTC thru Jun 19/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Closed low lingering across the Southeast through Wednesday, lifting back into Central Appalachians by Thurs... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average 07Z update: The 00z UKMET and CMC both trended back toward the 00z GFS/NAM positions through the length of the short-term to support a high confidence general model blend. ---Prior Discussion--- Guidance continues to be well clustered with the evolution of the eastern US closed low. Obviously, smaller scale affects of convection and minor mass differences/strength of the ridge to the north play a larger role in the model spread by day 3. For example, the 12z UKMET drifts north a bit faster due to finding the greatest weakness/ridging relative to the closed low to the NW and the ridge to its north. It is minor and within the realm of possibilities but drifts out of best consensus and continuity, to perhaps weight a bit lower. Equally, the CMC is a bit weaker too. So from a blending/confidence perspective, a stronger/tighter blend of the 00z GFS/NAM and 12z ECWMF will provide higher prescience to the forecast, but a general model blend would be acceptable to account for the inherent uncertainty in any closed low. Given the overall smaller spread and continued solid verification of the system with the guidance, will support the higher precision in a 00z GFS/NAM and 12z ECMWF blend. Confidence is above average given smaller overall spread in the guidance suite including ensemble solutions. ...Closed low moving into the Northwest Tuesday into the Northern High Plains by Thurs... ...Northern Plains surface lows/N-S frontal zone... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend up to 60hrs (18.12z) 00z UKMET/ECMWF blend (incl GEFS/ECENS if desired) Confidence: Average to slightly above average 07Z update: The 00z CMC is a bit weaker through the base of the approaching trof which leads to later binary interaction with the northern portion of the larger scale circulation over S Canada. This leads to a slight west and south drift relative to the ensemble mean which continues to be best represented by the ECMWF/UKMET. As such will continue a general model blend ending around 18.12z shifting toward a 00z ECMWF/UKMET blend thereafter. Some inclusion of the 00z GEFS/12z ECENS may help to account for some uncertainty if desired. ---Prior Discussion--- Broad trof/closed low over the Pacific NW will continue to shift eastward, the leading shortwave/height-falls will expand eastward and allow the secondary/main inner core to the closed low to sharpens the trof as a whole through the Snake River Plain, before consolidating across the Southern Prairies of Canada. The evolution looks quite consistent and realistic through 60hrs (18.12z) but biases start to manifest and lead to increased spread. The 00z GFS shows a faster evolution, which pulls it outside of the ensemble suite, while the 00z NAM retains a more compact base to the trof, leading to a slower and stronger surface wave emerging into the Plains late Thursday into Friday; both typical of known negative biases. The 12z ECMWF appears to have a northward bias within the ensemble suite and remaining guidance but combined with the UKMET/CMC through the depth of the troposphere seems a prudent with mild to above average confidence in the resultant blend. Gallina Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml