Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
138 PM EDT Thu Aug 08 2019

Valid Aug 08/1200 UTC thru Aug 12/0000 UTC

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

12Z Initial Model Evaluation with Preliminary Preferences and
Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend, lesser weight given to the 12Z
GFS/UKMET
Confidence: Average

Models are in fairly good agreement in terms of the mass fields. A
trough will approach the west coast while ridging across the
Plains slides slowly east and flattens as mid-level impulses help
to lower heights across the northern Rockies.  The trough in the
east will deamplify as the ridge approaches and the energy shifts
farther north. A broad-based model blend is preferred for mass
fields across North America...with more focus on higher resolution
guidance for QPF.

Differences were noted across the Pacific Northwest associated
with the trough and energy moving around the northern tier of the
ridge axis Saturday into Sunday.  The 12Z GFS was slightly out of
tolerance compared to the model suite and ensembles in terms of
timing and intensity of the upper low and mid-level energy. Though
it is within the model clustering.  Also, the 12Z UKMET appears to
be more amplified with the mid-level trough axis off the east
coast during the weekend with a slightly flatter flow pattern
across the Great Lakes region.  These difference do not appear to
impact the resultant precipitation. 

Given this, preference was toward a general model blend CONUS
wide, with lesser weight on the 12Z GFS in the Pacific Northwest
and lesser weight toward the 12Z UKMET in the northeast. 

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

Weiss/Pagano