Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 243 PM EDT Thu Jun 21 2018 Valid Jun 21/1200 UTC thru Jun 25/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z initial model evaluation...including preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Upper low over the Midwest evolving into open trough over Northeast U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~ Preference: General model blend Confidence: Above average The 12Z NAM has trended close enough to the model consensus compared to last night and a blend of the deterministic guidance works well with this system. First trough over northern Rockies and Dakotas through Friday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in rather good agreement with the first trough that crosses the Northwest and then advances downstream across the Plains and Midwest through Saturday and Sunday, and therefore a general blend of the deterministic guidance suffices. Upper low developing over northwest U.S. this weekend ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12z GFS/00Z ECMWF Confidence: Average A second upper level trough will arrive across the Northwest by Saturday and amplify into a closed low which drops down across the Intermountain West by Sunday. By the end of the period, the 00Z CMC is likely a little slow with its closed low evolution, whereas the 12Z NAM slightly more amplified with its height falls spilling out across the Plains. The 12Z UKMET appears slightly slower with the arrival of the upper low over the northern Rockies. The 12Z GFS and 00Z ECMWF are reasonably well clustered and tend to reflect the model consensus, so a GFS/ECMWF blend will be preferred with the second trough. Upper level trough affecting New England by Sunday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/00Z ECMWF Confidence: Above average The next upper trough begins to arrive from Ontario and Quebec on Sunday across New England. The 12Z NAM is slightly faster than the model consensus whilst the 12Z UKMET is slightly more amplified. The GFS and ECMWF agree well with the ensemble means and are a prudent choice for this feature. Weakening low center/MCV over the lower Rio Grande Valley ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in very good agreement with the details of this weakening system. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml D. Hamrick