Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1225 AM EDT Fri Jul 27 2018

Valid Jul 27/0000 UTC thru Jul 30/1200 UTC

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

00Z model evaluation...with preferences and confidence
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...Overall Synoptic Pattern across the CONUS...
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Preference: Blend of the 00Z GFS and 12Z ECMWF
Confidence: Slightly above average

The upper pattern across the CONUS for the next 3 days will again
feature general troughing over essentially the eastern 2/3rds of
the nation with a nearly stationary ridge centered over the
Southwest. An upper trough and weak associated closed low is
expected to be focused just offshore the Pacific Northwest by the
end of the period. By this weekend, a cold front will progress
through the Great Lakes and gradually slow down as it approaches
the East Coast. The same boundary is expected meanwhile to be
draped back to the southwest down across the southern Plains where
it will be quasi-stationary. By Sunday, a wave of low pressure
will be developing along the front across the TX panhandle and
will begin to advance off to the east. Disturbances meanwhile in
northwest flow aloft on the north side of the ridge will advance
across the central Plains through the period and support multiple
convective complexes each day.

Differences with the guidance include the 12Z UKMET being a bit
too far north with its front across the southern Plains compared
to the 00Z NAM/GFS and the 12Z CMC/ECMWF solutions. The 00Z NAM
also appears to be a bit too deep with its troughing over the
Great Lakes and Midwest on Sunday and Monday. Overall, the better
model clustering and ensemble support still favors the GFS/ECMWF
camp, and so a blend of these solutions will be preferred for the
mass fields.

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

Orrison