Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1235 PM EDT Tue Sep 24 2019

Valid Sep 24/1200 UTC thru Sep 28/0000 UTC

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

12Z Model Evaluation with Preferences and Forecast Confidence
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...Overall Pattern Across the CONUS...
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Preference: General Model Blend
Confidence: Above average

The synoptic pattern expected over the CONUS through the next 3
days will feature troughing confined to the northern and
northwestern US while ridging persists over the southeast. A
closed upper low over the southwest US will become absorbed into
the troughing and move into the central Plains by the end of Day
3.

Global deterministic model guidance is in above average agreement
through the next 3 days with the large scale features and
evolution. The closed low over the southwest US will stall through
Day 2, shedding vorticity impulses into the northern stream
energy. Eventually the whole system becomes absorbed by the end of
Day 3 as a stronger closed low drops into the Pacific NW. This
will amplify the pattern by the end of the forecast period.

One shortwave trough moving through the northern Plains on Day 3
will spawn a surface low that tracks into the Upper Midwest with
its associated cold front marching through the central Plains and
mid-MS River Valley. Here, there are some subtle model differences
in the low track position and speed. The 12Z GFS is a touch faster
than the non-NCEP guidance and the 12Z NAM is displaced further
north than the consensus. Guidance is in pretty good agreement on
the cold front position through Day 3.

With this in mind, a general model blend is preferred given the
above average agreement and run to run consistency the last
several cycles.


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

Taylor