Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1258 PM EDT Wed Sep 19 2018

Valid Sep 19/1200 UTC thru Sep 23/0000 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 and 00Z ECMWF
Confidence: Slightly above average

The biggest difference across the lower 48 through Saturday
involves the track of a mid-upper level trough from the western
U.S. into the north-central U.S. for Thursday and Friday. Out
ahead of this trough, low pressure will organize along a front and
track through the Great Lakes region and eventually into Ontario
for Friday morning. The 12Z NAM/GFS solutions are reasonably well
clustered with the 00Z CMC/ECMWF solutions with the evolution of
the energy aloft and the surface cold front. The 00Z UKMET though
leans toward the slower side of the model suite with the mid/upper
level trough and the surface low reflection as it crosses through
southern to southeast Canada. The UKMET is also the deepest model
solution with the surface low. Will suggest a blend of the better
clustered 12Z GFS and 00Z ECMWF.

Some modest timing differences remain with the next mid-upper
level trough arriving over the Pacific Northwest by Friday into
Saturday. Overall, a general model blend will be preferred here
with the best weighting toward a 12Z GFS/00Z ECMWF blend.

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

Orrison