Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
120 AM EDT Fri May 17 2019

Valid May 17/0000 UTC thru May 20/1200 UTC

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

00Z NAM/GFS Evaluation with Preliminary Preferences and Forecast
Confidence
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...Overall Pattern across the CONUS...
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Preference: 00Z GFS, 12Z ECMWF, 12z UKMET blend
Confidence: Slightly above average

Two large mid-upper level troughs will dominate the pattern across
the CONUS through Sunday night with the first reaching the Central
and Southern Plains later today, invoking cyclogenesis across
Nebraska by evening. A second surface low is expected to form on
Saturday in Kansas as a shortwave in the base of the trough axis
moves out from the Rockies. It is with this second low that
differences develop. However, ensembles show better agreement
today compared to yesterday for a middle ground between the
somewhat slower/southern 00Z GFS and the similar 12Z ECMWF/UKMET
with the 12Z CMC in the middle through Sunday morning. Only the
00Z NAM differences significantly here until Sunday evening when
the 12Z CMC starts lagging the model consensus across the Upper
Midwest. A 00Z GFS, 12Z ECMWF, 12Z UKMET blend should work well
across the Great Plains to the Midwest.

Regarding the next trough set to reach the West Coast Saturday
night, there are only minor timing/amplitude differences on the
synoptic scale with smaller scale detail differences yet to be
resolved. Given the general agreement, at this time, a general
model blend will be preferred through Monday morning.

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

Otto