Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1242 PM EDT Mon Jul 22 2019 Valid Jul 22/1200 UTC thru Jul 26/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation, Including Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Pacific Northwest/Far Northern Plains... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...though 60 hours Non-GFS blend...after 60 hours Confidence: Slightly above average The latest models take a portion of the upper trough offshore the Pacific Northwest off to the east over the next few days along with a cold front. The bulk of this energy will traverse southern Canada, but the southern end of the height falls will clip the far northern Plains and will allow a cold front to cross this region. The 12Z GFS is a tad faster than the remaining models and tracks its surface low a bit south of the model consensus. The ensemble means per the GEFS and ECENS suites tend to favor a a non-GFS blend after about 60 hours. Will prefer a general model blend through 60 hours as a result, and a non-GFS blend thereafter. ...Four Corners... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 06Z GEFS mean and 00Z ECENS mean Confidence: Above average The guidance is overall in very good agreement with the development and persistence of a rather strong mid-level ridge over the Four Corners region which will be instrumental in advecting monsoonal moisture northward through the period as the monsoon season begins to take shape. There is some spread with the strength of the ridge toward the end of the period as the 12Z GFS gradually becomes the weakest solution. On the flip side, the 12Z UKMET becomes the strongest, with the remaining guidance in between camps. Based on the latest GEFS mean and ECENS mean solutions which are very well clustered, the UKMET and GFS appear to be outliers. Will prefer a consensus of the ensemble means at this point. ...Remainder of the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The overall model spread is minimal through the period with both the temporal and spatial evolution of a cold front and related waves of low pressure advancing along it as the front moves into the East. This will all be in relation to an impressive longwave trough digging southeast that will envelope roughly the eastern third of the nation. The 12Z NAM is perhaps a tad too deep with the energy digging down across the interior of the southern Mid-Atlantic and Southeast, and periodically may be a bit too strong with its surface wave activity, but the guidance is generally in good agreement with the details of the front and the waves of low pressure. A general model blend will be preferred as a result. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Orrison