Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1234 AM EDT Fri Sep 28 2018

Valid Sep 28/0000 UTC thru Oct 1/1200 UTC

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

00Z Initial Model Evaluation...with Preferences and Forecast
Confidence
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...Overall Preference for the Entire CONUS...
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Preference: 00Z GFS/12Z ECMWF/12Z UKMET
Confidence: Slightly above average

A large scale upper level trough encompasses much of the northern
U.S. and Canada on Friday with a rex block over the eastern
Pacific and an upper ridge over the central Atlantic and the
Desert Southwest.  By Saturday evening, more of a quasi-zonal flow
pattern is expected to become established across the northern tier
states and the upper low making its way to northern California and
southern Oregon, and ridging over the Gulf of Mexico.  The western
U.S. upper low should become absorbed by the mid-latitude
westerlies by Sunday evening.  A large surface high will be
settling in across the central and eastern U.S. by this weekend
with a new surface low and frontal boundary developing over the
High Plains by Sunday and this front should extend towards the
Great Lakes.

The models and ensemble means are in very good agreement on the
mass fields through Saturday morning.  After this time, the CMC is
displaced to the south of the model consensus with the upper low
approaching the West Coast, and by Sunday the GFS is quicker with
the shortwave trough crossing Manitoba and Ontario, and the NAM on
the slower side of the model guidance with that same feature. 
Otherwise, the GFS is close to the model consensus and it can be
incorporated along with the ECMWF and UKMET.

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

D. Hamrick