Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1236 AM EDT Mon Sep 24 2018

Valid Sep 24/0000 UTC thru Sep 27/1200 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: Blend of the 00Z GFS/12Z ECMWF
Confidence: Slightly above average

The models and ensemble means are indicating a transition to an
amplified flow pattern across Canada and the northern half of the
U.S. by the middle of the week as the northwestern U.S. upper
trough builds and becomes firmly established over the northern
plains and Upper Midwest.  This trough will be bounded by two
upper highs off both coasts of the U.S. as the synoptic scale
pattern becomes more blocked.  A few shortwave perturbations
traversing the base of the trough will support surface lows and
accompanying fronts during the short range forecast period.

Most model guidance is in good agreement synoptically, however the
12Z CMC is faster with the cold front crossing the Great Lakes and
central plains on Tuesday.  Regarding the disturbance approaching
the Carolinas by midweek, the 12Z UKMET and to an extent the 12Z
ECMWF are the stronger solutions compared to the model consensus
with the UKMET farthest left/west with the track and also slower. 
The UKMET is also faster with a surface low tracking southward
from central Canada on Wednesday.  The consensus of the guidance
besides the UKMET is that this energy should remain just off the
East Coast and begin to recurve by the end of the period out ahead
of the cold front approaching the East Coast by late Wednesday.

Based on the latest model clustering, ensemble guidance and
trends, the GFS and ECMWF are close to the model consensus and a
blend of these solutions will be preferred at this time.

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