Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1239 AM EDT Sat Jul 4 2020 Valid Jul 4/0000 UTC thru Jul 7/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Trough building over the Northeast U.S. this weekend ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through Sunday afternoon, then non-UKMET blend Confidence: Moderate-High A pair of shortwave troughs are expected to move through the Northeast over the next few days, with the first arriving by Saturday morning. A general model blend for mass field purposes is sufficient here. A second shortwave trough then arrives by late Sunday, and is expected to clip the northern areas of the Northeast and across New England. The CMC, GFS, and UKMET are more amplified with this trough as it crosses the region and then offshore, with the UKMET indicating the slowest solution. Trough over the Gulf Coast region ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: GFS/ECMWF blend Confidence: Moderate A slight weakness in the upper level ridge anchored over the central/southern Plains expands further during the course of the period as several convectively enhanced MCVs settle over the lower MS river valley and Gulf Coast region (while the ridge upstream retreats to the southwest U.S.). The synoptic pattern is largely agreeable though the UKMET is a little stronger with the upper ridge compared to the other guidance. The ECMWF and GFS are close enough to their respective means to merit a blend of those two models. Pair of troughs affecting the Northwestern U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: GFS/ECMWF blend Confidence: Moderate The flow pattern across the northwestern quadrant of the nation is expected to remain active as a large scale trough remains in place across the region. The first shortwave tracking across the Pacific Northwest on Saturday is expected to reach Manitoba by Monday morning, and this will support a cold front crossing the northern High Plains. The models are in decent agreement with this first system. A second shortwave reaches the Pacific Northwest by Monday afternoon as the overall pattern amplifies some. The GFS is slightly faster and the CMC is a bit slower, and a stronger solution with the UKMET by Tuesday morning. As a compromise and consensus, a blend of the GFS/NAM/ECMWF is preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hamrick