Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1252 AM EDT Sun Sep 23 2018

Valid Sep 23/0000 UTC thru Sep 26/1200 UTC

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

00Z Initial Model Evaluation...with Preferences and Forecast
Confidence
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...Overall preference for the entire CONUS...
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Preference: General model blend
Confidence: Slightly above average

The models and ensemble means are indicating a transition from a
quasi-zonal flow pattern across the northern tier of the nation to
more amplified by Tuesday night as the Pacific Northwest trough at
the beginning of the forecast period grows stronger as it tracks
eastward.  This in turn will fortify the upper ridge situated over
the western Atlantic and a closed upper high over the northeast
Pacific.  Shortwave perturbations around the base of the
large-scale central U.S. trough will be the main weather makers
through the first half of the work week.

The models show only modest timing and amplitude differences with
respect to the wave of low pressure that should lift up across the
Upper Midwest Sunday night and into Monday, with the NAM among the
faster solutions. The NAM and CMC are a little faster to bring the
front southeast across the middle MS Valley and southern Plains
compared to the other models.  A multi-model blend is preferred to
deal with placement differences, with greater weighting towards
the UKMET and ECMWF.  With respect to the lingering mid level low
currently over the southern Plains and lower MS Valley, this
system should gradually weaken and begin to dampen out over the
next couple of days.

Based on the latest model clustering, trends and ensemble
guidance, a general model blend will be preferred with all of
these features and the large scale pattern across the CONUS.


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

D. Hamrick