Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
240 PM EDT Wed Sep 19 2018

Valid Sep 19/1200 UTC thru Sep 23/0000 UTC

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

12Z Model Evaluation...with latest preferences and confidence
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...Overall preference for the entire CONUS...
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Preference: General model blend
Confidence: Slightly above average

The biggest difference across the lower 48 through Saturday
involves the track of a mid-upper level trough from the western
U.S. into the north-central U.S. for Thursday and Friday. Out
ahead of this trough, low pressure will organize along a front and
track through the Great Lakes region and eventually into Ontario
for Friday morning. The 12Z NAM/GFS solutions are reasonably well
clustered with the non-NCEP solutions of the 12Z CMC/UKMET and CMC
solutions with the evolution of the energy aloft and the surface
cold front. Although the NAM and a bit more so the GFS tend to be
a bit more progressive than the non-NCEP camp. Also, there is a
period around between 30 and 42 hours where the GFS exhibits some
convective feedback across areas of east-central MN to northern WI
and the U.P. of MI. Elsewhere, some modest timing differences
remain with the next mid-upper level trough arriving over the
Pacific Northwest by Friday into Saturday. Overall, a general
model blend will be preferred across the CONUS based on the latest
spread, trends and clustering of solutions.

...T.D. Nineteen-E...
...Energy cutting off over the Southern Plains...
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Preference: Blend of the 12Z GFS and 12Z ECMWF
Confidence: Slightly above average

T.D. Nineteen-E developed as of 15Z this morning and is centered
over the Gulf of CA. The system is forecast to lift north and then
north-northeast into mainland Mexico within the next 12 to 24
hours before dissipating. A mid level trough just west of the the
Baja Peninsula though will advance east and capture the mid level
energy of Nineteen-E and advance gradually northeast across
northern Mexico, southern New Mexico and then out into the
southern Plains through Thursday and Friday. By later Friday and
Saturday, the system will become cut off from the westerlies and
will be caught between a subtropical ridge developing over the
Four Corners region and a subtropical ridge over the Southeast
U.S. Meanwhile, the energy will be interacting with the tail end
of a front stalling out near or to the south of the Red River. On
the large scale, the models exhibit rather good model mass field
agreement. So, in this regard, a general model blend led by a
GFS/ECMWF consensus will be preferred. However, there are key
differences with QPF placement and amounts over portion of
especially OK/TX on Friday and Saturday. Please consult the latest
QPFERD for more details on the expected rainfall and flash
flooding hazards. In the short-term, please also consult the
latest NHC forecast advisories/discussions concerning T.D.
Nineteen-E.

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

Orrison