Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
237 PM EDT Thu Aug 23 2018

Valid Aug 23/1200 UTC thru Aug 27/0000 UTC

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

12Z Model Evaluation...with Preferences and Confidence
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...Overall Synoptic Pattern across the CONUS...
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Preference: General model blend
Confidence: Average

For most of the larger scale systems, the 12z models have good
agreement through day 2, and even day 3 with the trough moving
from the Great Lakes across the northeast.
Consequently, any combination of the NAM, GFS, UKMet, ECMWF and
Canadian Global will suffice to mitigate minor differences. 

Further upstream, there are still some differences regarding the
timing of the trough moving across the Northwest, northern Rockies
towards the high northern Plains late Sat-Sunday.  By Sunday
morning, the NAM, ECMWF and UKMet are more progressive -- moving
energy eastward through the base of the trough into the northern
Rockies, whereas the GFS and Canadian are a few hours slower.  The
continuing spread lends support to a model compromise here until
better clustering develops.  However, the strong upstream high
shown by the models over the northeast Pacific may support a
slower and more amplified downstream trough -- suggesting the NAM,
ECMWF and UKMet may be too fast.

The 12z ECMWF formed a closed 700 mb low near the MT/ND border 00z
Mon, which is stronger than the 00z run/00z ECMWF ensemble mean
and stronger than the 12z Canadian global/GFS/UKMET/NAM, so
confidence is low whether the strengthening in the 12z ECMWF will
be correct.

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

Petersen