Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1250 AM EDT Sat Aug 11 2018

Valid Aug 11/0000 UTC thru Aug 14/1200 UTC

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

00Z NAM/GFS evaluation with preliminary preferences
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...Overall Synoptic Pattern across the CONUS...
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Preference: 00Z GFS, 12Z ECMWF and 12Z CMC blend
Confidence: Average

There are three main upper trough/closed low features to key in on
for the short range. An upper trough will develop over the upper
Ohio Valley by Sunday morning and slowly progress east through
Tuesday, while the second feature will manifest as an upper
trough/closed low over the southern High Plains which slowly
advances northeastward into the central Plains. The third feature
is a closed low currently advancing toward the Pacific Northwest
which is expected to open up into a positively tilted trough axis
to move across southern Canada and the north-central U.S. through
Tuesday morning.

Out east, the 00Z NAM is a bit faster late Saturday into Sunday to
advance an 850-700 mb low into the Northeast, with a good
consensus to be slower. The differences in the NAM fade into
Monday/Tuesday, but the 12Z UKMET becomes notably slower/flatter
with the 700-500 mb low approaching the Northeast. The 00Z GFS,
12Z ECMWF and 12Z CMC show similarly and match the ensemble means.

Across the Plains, there are minor differences in placement
between each model, but overall agreement is good enough to
support a general model blend. In the Northwest, only the 00Z NAM
stands out from the remaining guidance with less mid-level energy
hanging back across Washington/Oregon.

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

Otto