Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
102 PM EDT Tue Sep 18 2018

Valid Sep 18/1200 UTC thru Sep 22/0000 UTC

...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...

12Z Model Evaluation...with latest Preferences and Confidence
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...Overall preference for the entire CONUS...
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Preference: Blend of the 12Z GFS/00Z ECMWF...overall CONUS
            12Z GFS/06Z GEFS mean blend...Pacific Northwest
Confidence: Average

The biggest differences across the lower 48 through Friday
involves the track of a mid-upper level trough from the western
U.S. into the northern Plains by the end of the week. Out ahead of
this trough, low pressure will organize along a front and track
through the Great Lakes region and into Canada. A 12Z GFS/00Z
ECMWF blend is recommended given this blend is closest to the
ensemble mean positions and holds good continuity with the
previous WPC preference. By late in the period on Friday, the 12Z
NAM begins to get a little slower than the model consensus over
the Great Lakes region with the timing of the upper trough.
Meanwhile, there are some notable differences across the Pacific
Northwest with the next upper trough arriving. The 00Z CMC is the
fastest solution and rather deep, versus the 00Z ECMWF and 00Z
ECENS mean which are the slowest. The 12Z GFS and 06Z GEFS mean
are well clustered and close to the model consensus, so a blend of
these solutions will be preferred by Friday across this region.

Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

Orrison