Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1248 AM EDT Thu Oct 04 2018

Valid Oct 04/0000 UTC thru Oct 07/1200 UTC

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

00Z Model Evaluation...with latest Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of the 12Z ECMWF/12Z ECENS mean/18Z GEFS mean
Confidence: Slightly above average

A series of shortwave troughs will traverse the Western U.S. over
the next few days and then eject/shear out across the
central/northern Plains. This will include the initial southern
stream energy/close low over the Southwest which will de-amplify
early on Thursday across the Four Corners region. Meanwhile, at
least two northern stream shortwaves will cross the Pacific
Northwest with the latter piece of energy expected to amplify
Saturday and Sunday rather vigorously over the Intermountain West
and setting the stage for a deep longwave trough over the Western
U.S. which will include a closed low evolution by the end of the
period. Meanwhile, all of the models show development of a rather
strong subtropical ridge over much of the southeastern third of
the country going into the weekend.

Model spread is noted with the evolution of a surface low lifting
up toward the Great Lakes region by early Saturday as the 00Z NAM
is a little slower with this feature and the 12Z UKMET is faster.
The 00Z GFS, 12Z ECMWF/CMC solutions are clustered in between
camps. Elsewhere, by the end of the period, there are some detail
differences with respect to the depth of the trough over the
Western U.S. as the GFS tends to dig energy a bit farther south,
but is overall not quite as deep as the remaining guidance. The
NAM was seen as perhaps not digging enough energy down to the
south over the Great Basin. The 12Z ECMWF, 12Z ECENS mean and 18Z
GEFS mean actually tend to best approximate the model consensus,
so in essence a general model blend will be preferred, but led by
a blend of the ensemble means and the 12Z ECMWF at this time. This
preference will suffice for the CONUS.

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

Orrison