Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1250 PM EDT Fri Jun 29 2018

Valid Jun 29/1200 UTC thru Jul 03/0000 UTC

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

12Z NAM/GFS evaluation...including preliminary preferences
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...Longwave trough moving eastward from the western U.S. to the
northern Plains and Great Lakes this weekend with accompanying
cold front...
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Preference: General model blend
Confidence: Average

Overall with mass fields, there were no significant differences
noted.


...Weak mid-level low retrograding from the Southeast coast this
morning to the central Gulf Coast Monday morning...
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Preference: Non 00Z CMC blend
Confidence: Slightly below average

While the 12Z GFS is the weakest at 500 mb with this feature along
the Gulf coast, it is not out of line enough from the remaining
deterministic consensus to exclude it from part of a blend. Only
the 00Z CMC differs significantly with the CMC keeping the
mid-level vorticity center farther east by Monday across the
South, compared to the remaining deterministic and ensemble
guidance.

While the models all show reasonable agreement today, they all
showed reasonable agreement yesterday as well, but today's
guidance has largely shifted south valid Saturday and Sunday
evening. Future shifts are possible which lowers confidence
despite generally good agreement outside of the 00Z CMC between
the deterministic guidance and the ensemble means.


...Next upper level trough/low forecast to set up over the
Northwest U.S. by Monday evening...
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Preference: Non 12Z NAM blend
Confidence: Slightly above average

The 12Z NAM is quicker to bring mid-level height falls into the
Northwest compared to the remaining available guidance. It is not
atypical for the NAM to differ by 84 hours out into the forecast
in the Northwest and given it lies on the very fastest edge of
available GEFS/ECMWF/CMC ensemble members, will exclude the NAM
from the preference.


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

Otto