Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1224 PM EDT Fri May 17 2019

Valid May 17/1200 UTC thru May 21/0000 UTC

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

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

...Overall Pattern across the CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 12z GFS, 00z ECMWF, 00z UKMET east of the Rockies
            General model blend (non-NAM) western US
Confidence: Slightly above average

A few large mid-level troughs will be the main driving factors for
sensible weather across the CONUS through the next 3 days. The
initial trough, currently over the interior West, will push into
the central Plains and lead to cyclogenesis later today. The next
trough advances into the western US Sunday followed quickly by
another trough on Monday or Tuesday.

For the first system, the latest model guidance shows very good
agreement with the surface low track from Nebraska into southwest
Minnesota through the next 24 hours. Bigger differences creep up
Saturday night into Sunday morning with a secondary area of low
pressure across the Mid and Upper MS River Valleys. The NAM is
quickest to eject out into the Upper Midwest, well ahead of the
rest of the guidance. This leads to a quicker progression of the
QPF distribution. The UKMET is also faster than the rest of the
model guidance. Looking at the GEFS and ECENS, the deterministic
runs lie within the ensemble means, and are also show very good
agreement to each other. The 00z CMC is also not too different and
some inclusion of it can be incorporated. Overall, the WPC
preference is for a non-NAM, non-UKMET solution (GFS/ECMWF/CMC
blend).

Out west for the second and third shortwave troughs through early
next week, there is fairly good agreement with the 500 mb heights
through Monday night. By the end of the period, low tracks and
positions vary, especially for the low moving into the Pacific
Northwest area. These mass field differences do not lead to
significant QPF differences, and for those areas, a general model
blend can be applied.

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

Taylor