Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 115 AM EDT Wed Jun 26 2019 Valid Jun 26/0000 UTC thru Jun 29/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z NAM/GFS Evaluation...with Preliminary Confidence and Preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Exception: 00Z GFS/12Z ECMWF blend across Northern Plains/Great Lakes Confidence: Below Average The upper flow at the start of the period features a large closed low just off of the Pacific Northwest coast with zonal flow downstream across the northern tier of the U.S. and an elongated closed low over northern Ontario. By Saturday morning, the slow moving closed low off of the Northwest U.S. does move inland while elongated northeast to southwest, building a ridge downstream across the central High Plains to the northern Plains. Meanwhile, the closed low over northern Ontario maintains its position, while a broad/weak upper trough expands from the lower Mississippi Valley into the western Gulf of Mexico. The only area of significant disagreement with this pattern is regarding a convectively enhanced area of mid-level vorticity that begins over the central to northern High Plains Wednesday evening and moves downstream toward the upper Mississippi Valley for Thursday afternoon. There are latitude differences with this feature, with the 00Z GFS breaking its previous continuity and joining the consistent northern camp of the 00Z NAM and 12Z UKMET. The 12Z ECMWF/CMC have also been consistent but track to the south. It appears the NAM/UKMET have gridscale feedback which may cause their mid-level vorticity maxima to track too far north. There is a consistent signal for convection north of the synoptic frontal boundary in easterly low level upslope flow and modest CAPE. Here, the ECMWF/CMC may be too weak, which is why a middle ground between the northern and southern camps is preferred at this time. That represents a blend of the 00Z GFS and 12Z ECMWF. Please reference the WPC Excessive Rainfall Outlook for further details regarding this area of the U.S. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Otto