Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1250 AM EDT Mon Apr 29 2019

Valid Apr 29/0000 UTC thru May 02/1200 UTC

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

00Z Model Evaluation...with Preliminary Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: 0z UKMET/GFS and 12z ECMWF blend
Confidence: Slightly above average

Overall see pretty good agreement amongst the guidance on the
synoptic scale over the next three days. Would say that components
of the 0z NAM and 12z CMC stand out as outliers and less likely
outcomes. The NAM ends up stronger with embedded shortwave energy
within the Intermountain West on Tuesday, which ends up resulting
in it also being stronger with energy across the northern Plains
on Wednesday. These differences with the embedded shortwave energy
result in a slightly different evolution of the larger scale
trough and sensible weather impacts across the Rockies/Plains by
later Tuesday through Wednesday night. The NAM is on its own and
trends seem to be against it as well...thus while I would not call
the NAM an extreme outlier...it is different enough to be removed
form our preferences at this time.

The 12z CMC ends up slower with the progression of the longwave
trough into the Plains, and it also has little support from other
guidance or recent trends. Thus would consider it a less likely
solution.

While there are some differences amongst the 12z ECMWF and 0z
GFS/UKMET, they are generally minor and a look at the past several
runs of each shows a convergence of solutions. Thus from a large
scale standpoint, think a blend of these models should suffice at
this time...with most of the spread amongst these solutions the
result of less predictable convectively driven factors.


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

Chenard