Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
226 PM EDT Thu Apr 25 2019

Valid Apr 25/1200 UTC thru Apr 29/0000 UTC

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

12Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend (weighted toward the 12Z GFS/12Z
ECMWF)
Confidence: Slightly above average

There are three systems during this time with which the models
contend. Overall, there is generally good model agreement with the
mass fields of each, with instability playing a part in placement
of QPF.

The first system is the long wave trough tracking from the Lower
and Mid MS Valley as it takes on a negative tilt before exiting
New England before 29/00z. Both the 12Z NAM/GFS are close to the
consensus with this feature, and the surface low that spins up
ahead of it. Based on the clustering with this system, forecast
confidence is slightly above average.

The second system is the short wave energy tracking from British
Columbia at 26/12z to New England by 29/00z, as it elongates into
a long wave trough. Again, the 12Z NAM/GFS are close to the
consensus with the timing and evolution of the long wave trough.
There are some fairly minor timing issues with the surface low
associated with the mid level feature as it moves from the OH
Valley at 28/00z to a position of the central New England coast by
29/00z. The differences, however, are not enough to eliminate any
solution from the preference.

The final system is closed mid level low moving from the Gulf of
Alaska early on Day 1 to a position over western ND by the end of
the period. Once again, both the 12Z NAM/GFS are close to the
consensus with this feature, as well as it surface low over
western ND. Because of this, a general model blend is preferred,
with slightly above average confidence. 


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

Hayes