Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
230 AM EDT Fri Apr 13 2018

Valid Apr 13/0000 UTC thru Apr 16/1200 UTC

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

00Z Model Evaluation with Final Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Long wave trough over the Rockies early Fri, amplifying across
the Plains/OH Valley Sat/Sun...
...Deep surface low developing Fri over the Plains, tracking to
the OH Valley Sat/Sun...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 00z NAM/00z ECMWF/00z UKMET/12z ECMWF Mean blend
Confidence: Slightly Above Average

The 00z NAM was close to the model consensus tracking the long
wave through across the Rockies early this morning, as it closes
off over the Central Plains tonight into Sat, before taking on a
negative tilt Sun. The 00z NAM is very close to the consistent 00z
ECMWF/12z ECMWF ensemble mean positions, both at the surface and
in the mid levels. After being on the fast side with the surface
and mid level features, the 00z UKMET has come back to the
consensus with both through Sun, and has been added to the
preference.

The 00z GFS was closer to the consensus through Sat, then becomes
faster with the mid level and surface systems by Late Sat into
early Sun. The faster speed affects the precipitation pattern and
temperatures in the column, so despite it coming closer to the
consensus, it is not yet ready to be included in the preference
because of the timing differences Sat into Sun. The same is true
with the 00z CMC, which is faster than the consensus, and it has
been speeding up the  movement of the surface low across the OH
Valley on Sun over the past three runs.


...Long wave trough slowly dropping into the Pacific Northwest Sat
into Sun...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General Model Blend
Confidence: Above average

Both the 00z NAM and 00z GFS were close to the consensus (though
the 00z NAM is a bit slower by the late Sun) with the evolution of
the mid level trough as it deepens and reaches the Pacific
Northwest late Sat into Sun. The 00z non-NCEP guidance was also
close to the consensus, so a general model blend was preferred.

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

Hayes