Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1231 PM EDT Sun Aug 19 2018 Valid Aug 19/1200 UTC thru Aug 23/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Height falls crossing the Lower Great Lakes/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average GOES-16 WV imagery shows multiple shortwave troughs crossing the upper OH Valley, lower Great Lakes and Northeast currently. The guidance gradually shifts the energy through the Northeast and offshore New England by late Monday. A general model blend will be preferred. ...Deep trough/surface low amplifying across the Plains/Midwest... ...Surface front pushing toward the Eastern Seaboard... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS, 00Z CMC and 00Z UKMET Confidence: Average An amplifying upper trough is seen over the central Plains currently along with a strengthening PV anomaly as noted in GOES-16 WV and Airmass RGB imagery. The models deepen this trough through tonight which will deepen low pressure initially over eastern KS through this evening before it then lifts up across far northwest MO and southwest IA through Monday morning. The 00Z ECMWF remains on the slow side of the model spread through early Monday, and is likely still too slow as it is now a little slower than its own ensemble mean. The guidance takes the upper trough and associated surface low northeast across the Midwest and Great Lakes region going through Monday and Tuesday with a trailing cold front that will cross the lower MS Valley. On Wednesday, the guidance agrees well in taking the front across the Eastern Seaboard as low pressure lifts up across southeast Canada. The 00Z ECMWF though tends to be occasionally slower and definitely south of the model consensus. The best model clustering with this system tends to lie with the 12Z GFS, 00Z CMC and 00Z UKMET for mass fields, and a blend of these solutions will be preferred. ...Trough digging across the Northwest through early next week... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through Tuesday Non-GFS blend...on Wednesday Confidence: Slightly above average A new upper trough and associated closed low digging across the Northwest will gradually cut off by Tuesday as ridging noses up north of it across southwest Canada. By Wednesday, the 12Z GFS tends to be lagging the model consensus as the system drifts toward the northern Rockies. A general model blend will be preferred through Tuesday, followed by a non-GFS blend thereafter. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison