Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
113 AM EDT Fri Aug 09 2019

Valid Aug 09/0000 UTC thru Aug 12/1200 UTC

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

00Z Preliminary Model Evaluation with Preliminary Preferences and
Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend, with less weight on 00Z NAM
Confidence: Average

Large ridge across the middle of the CONUS will be book-ended by
troughs across the Northeast and the Pacific NW. The global
consensus is generally well aligned with the primary trough axis
swinging through New England while the main upper low remains
displaced into Canada, with the second low diving into northern
California driving downstream ridge amplification across the
Plains. The NAM is several DM cooler with the ridge across the
Plains, and this seems unlikely due to lack of model support plus
the likelihood of ridging to enhance in response to the upstream
trough diving into California. Despite it being weaker with the
ridge, the overall pattern remains similar and has little impact
to QPF, so a minimalist weight approach seems best. Other than
that, a general model blend should suffice. The GFS is a bit
strong with shortwaves lifting into the Monsoon flow across the
SW, especially on day 3, so a GEFS solution to blend out some of
this amplitude may be best, but even then the overall spread is
minimal.

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

Weiss