Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1257 AM EDT Sat Apr 14 2018

Valid Apr 14/0000 UTC thru Apr 17/1200 UTC

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

00z NAM/GFS Evaluation with Initial Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Long wave trough over the Central Plains early today, becoming
negatively tilted into eastern CONUS Mon...
...Deep surface low over the Plains early today, occluding and
tracking into the Ohio Valley and Great Lakes into Mon...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 00z NAM/12z ECMWF/12z ECMWF Ensemble mean/12z UKMET
blend
Confidence: Slightly Above average

The 00z NAM remains close to the consensus as the closed low over
the Central Plains early today tracks into the Mid and Upper MS
Valley later today into tonight. The closed low takes on a
negative tilt across the OH Valley and the Great Lakes late Sun
into Mon. It is tightly clustered with the 12z ECMWF/12z ECMWF
mean and 12z UKMET. This cluster was also similar with the double
surface low structure over Quebec and northern New England Mon.

The 00z GFS remains faster with the mid level system, especially
during Sun into Mon, which results in issues with low level
temperatures and the western extent of precipitation. In addition,
the 00z GFS does not depict a closed surface low over NH/ME, as
the consensus does. Because of this, the 00z GFS, while coming
closer to the consensus, cannot be included in the preference
quite yet. Likewise, the 12z CMC remains faster than the
consensus. and for that reason was left out of the preferred
blend.


...Long wave trough slowly dropping into the Pacific Northwest
this weekend...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General Model Blend
Confidence: Slightly above average

Both the 00z NAM and 00z GFS were close to each other and the
consensus with the evolution and speed of the mid level trough
crossing the West Coast Sun, before reaching the Rockies Mon.
There were some minor detail differences across the Northern
Rockies, where some solutions closed off a mid level low (00z NAM,
12z UKMET) and other did not (00z GFS/12z ECMWF). However, the
differences were small enough to favor a general model blend with
this feature.


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

Hayes