Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1237 PM EDT Sun Sep 08 2019

Valid Sep 08/1200 UTC thru Sep 12/0000 UTC

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

12Z Model Evaluation with Preferences and Forecast Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall Pattern Across the CONUS...
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Preference: Non-GFS blend...Northern High Plains on Day 3
            General model blend...remainder of CONUS
Confidence: Average

The models are in good agreement with the large scale synoptic
evolution across the CONUS over the next few days. This will
involve the amplification of a deep trough across the western U.S.
on Tuesday and Wednesday, and a rather strong deep layer ridge
over much of the eastern U.S. with exception to parts of the
Northeast.

As the larger scale flow becomes more amplified with time, there
is little model spread noted with the shortwave energy currently
crossing the middle and upper MS Valley. This energy will dampen
out with time as it crosses the OH Valley and Mid-Atlantic region
through early Monday. There is also very little model spread with
the negatively tilted trough currently crossing the Intermountain
region which will cross the central and northern Plains on Monday
and dampen out as it encounters increasingly confluent
mid/upper-level flow downstream.

By later Tuesday and Wednesday, as the larger scale trough evolves
across the Intermountain West, the 12Z GFS again becomes more
progressive with its height falls, and especially at the end of
the period with its closed low over the northern High Plains. The
12Z NAM and 00Z non-NCEP model suite are all clustered well with a
slower solution which is also strongly supported by the latest
GEFS mean and ECENS mean.
 
Thus, the preference will be for a general model blend across the
CONUS, but with exception to the northern High Plains region on
day 3/Wednesday where the 12Z GFS will be dismissed, and a non-GFS
blend preferred.


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

Orrison