Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
138 AM EDT Tue Jul 23 2019

Valid Jul 23/0000 UTC thru Jul 26/1200 UTC

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

00Z Preliminary Model Evaluation, Including Preference and
Confidence
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...Pacific Northwest/Far Northern Plains...
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Preference: Non-NAM blend
Confidence: Slightly above average

A closed low will shed shortwave energy onto the Pac NW coast
Wednesday morning, before lifting E/NE across southern Canada
through day 3. The guidance is in very good agreement in both
intensity and timing of this feature with the exception of the
NAM, which is further south, especially by day when it digs the
shortwave back down into the Northern Plains. This pushes the
height falls and associated surface front further southeast into
the CONUS, and is on the edge of the ensemble envelope. For this
reason a Non-NAM blend is preferred due to the agreement of the
other available guidance.


...Four Corners...
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Preference: Non 00Z/GFS or 12Z/UKMET
Confidence: Slightly Above average

A strong ridge blossoming across the Four Comers will spin nearly
in place as the longwave ridge amplifies into western Canada. This
ridge will foster the development of Monsoonal moisture lifting
into the Southwest. Although the guidance is in good agreement
with the overall positioning of this ridge, by the end of the
period the GFS is the weakest with this ridge while the UKMET is
considerably stronger than the consensus mean. For continuity and
to account for these differences, a non GFS/UKMET blend which
includes the ensemble means is preferred.


...Remainder of the CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

A general model blend remains sufficient as the global suite is in
very good agreement with the spatial and temporal evolution of a
cold front and longwave trough digging across the eastern CONUS.
Minor differences exist in where the front and any waves of low
pressure may lie across Florida d2/3, but these create minimal
sensible weather differences noted by similar QPF outputs.
Therefore, a general blend is preferred.


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

Weiss