Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
236 PM EDT Sat May 18 2019

Valid May 18/1200 UTC thru May 22/0000 UTC

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

12Z Model Evaluation with Final Preferences and Forecast Confidence
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...Overall Pattern across the CONUS...
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Preference: 12z GFS/ECMWF blend
Confidence: Slightly above average

19z update: No significant changes noted with the rest of the 12z
guidance now available. The previous blend preference remains the
same as before.

---previous discussion---
Active and unsettled weather pattern is expected to continue over
the next 3 days for the central and western US as a series of
mid-level troughs move through the flow. In general, the pattern
will feature troughing over the west with a persistent ridge over
the southeast US. The first trough, currently moving out of the
Rockies will lead to another surface low tracking into the Upper
Midwest through tomorrow. This feature is reasonably well handled
by the latest guidance, though the 12z NAM is well ahead of the
rest of the guidance in its speed with the surface low. In the
mid/upper levels, the guidance is in good agreement. A lot will be
driven by mesoscale convective boundaries that play out later
today across the central Plains.

The next trough will swing through the Four Corners into the
southern/central Plains Monday and Tuesday. A few model
differences to note include the 00z UKMET is considerably slower
with its mid/upper trough axis (over NM) compared to the rest of
the guidance which is tightly clustered over TX/CO/KS. Meanwhile,
at the surface, more differences are noted. The NAM develops its
surface low much further east compared to the GFS and CMC. The
ECMWF is a good compromise for being 2-3 days out at this point.

Finally, a third trough moves into the Pacific Northwest and
California coast Tuesday. This feature is at the end of the
current forecast period and for the most part, there is fairly
good agreement in the large scale synoptic setup.

All in all, a blend of the GFS/ECMWF is preferred for the CONUS
mass fields, though the NAM can be included in the first 24-36
hours, especially over the central US. Less weight is given to the
GFS on Day 3, with its much further west surface low compared to
the model consensus. 


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

Taylor