Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1258 PM EDT Wed Jul 03 2019

Valid Jul 03/1200 UTC thru Jul 07/0000 UTC

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

12Z Preliminary Model Evaluation...with Confidence and Preferences
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...Overall Pattern Across the CONUS...
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Preference: Blend of 12Z GFS, 12Z NAM, 06Z GEFS, 00Z ECMWF
Confidence: Slightly above average


Models are in generally very good agreement in the overall
synoptic evolution over the next three days. A closed low over
Saskatchewan/Alberta will fill and lift northeast, while a
secondary piece of energy drops into the Pacific Northwest and
closes off, reinforcing the positively tilted trough across the
west. Downstream of this feature, an expansive mid-level ridge
will dominate the eastern 2/3 of the CONUS.

While the guidance is in good agreement with this setup, the UKMET
is much too warm with its 500mb heights within the ridge,
averaging 4-6dm higher than the global mean. With its heights
across Canada roughly the same, it is funneling more moisture on
stronger geostrophic flow into the Plains, and creating QPF that
is significantly higher than any other member, and should be
excluded from the blend. The CMC is very quick with its series of
impulses lifting through the trough and into the Plains,
especially with a strong feature on the 5th. While the overall
placement is within the ensemble envelope, it is temporally
displaced east by quite a bit, and should be used with caution as
it is these mesoscale features that will drive most of the QPF
across the country. The 00Z ECMWF and 12Z GFS/NAM are in good
agreement despite intensity differences of shortwaves moving
through the flow, and are weighted heavily in the blend. Do note
that the GFS is on the low-end of QPF forecasts across the Plains
by day 3, so a GEFS mean is also incorporated to trend towards
some of the higher QPF potential late in the period.

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

Weiss