Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1242 AM EDT Sat Jul 27 2019

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

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

00Z NAM/GFS Evaluation along with Preliminary
Confidence/Preferences
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Northern Tier of the U.S...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 00Z NAM, 12Z ECMWF and 12Z CMC blend
Confidence: Slightly above average

Models show that two shortwaves should skirt across the CONUS
Northern Tier during the short range. The first wave is forecast
to move from the Upper Midwest/Great Lakes early this morning to
central Quebec Sunday afternoon with the trailing frontal boundary
lingering across the north central U.S. The second shortwave and
associated cold front are currently moving into western British
Columbia and should reach the Northern Plains/Upper Midwest by
Sunday and the Great Lakes late Monday.

There remain some minor differences with the second shortwave,
mainly from the 00Z GFS which affects its surface low
strength/placement across the northern Great Plains Sunday
morning. Better agreement exists with the non-00Z GFS guidance,
but the 12Z UKMET is slightly faster than the consensus for a time
on Sunday. A blend of the 00Z NAM, 12Z ECMWF and 12Z CMC agrees
best with the ensemble means.


...Remainder of the CONUS including the Southwest...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Slightly above average

No significant mass field differences were noted with the
southwestern ridge and the remainder of the U.S., with a general
model blend preferred to iron out smaller scale differences.

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

Otto