Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1231 AM EDT Mon Apr 16 2018

Valid Apr 16/0000 UTC thru Apr 19/1200 UTC

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

00Z NAM/GFS model evaluation and initial preferences
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...Deep occluded cyclone tracking into Ontario/Quebec Mon/Tue,
becoming
centered over New England Wed...
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Preference: General model blend
Confidence: Slightly Above Average

Both the 00Z NAM/GFS are close to each other and the consensus
with the initial surface low tracking into southeast Ontario and
southwest Quebec Mon into Tue, as well as tracking a secondary low
into northern New England Wed. because of this, a general model
blend remains preferred, with slightly above average confidence.


...Long wave trough crossing the Northern Rockies Mon, reaching
the Plains and OH Valley Tue/Wed...
...Surface low tracking from KS into the Ohio Valley/Great Lakes
through late Wed...
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Preference: 00z NAM/12Z ECMWF/UKMET
Confidence: Average

The 00z NAM remains near the consensus with the long wave trough
crossing the Northern Rockies Mon and Mon night, with a closed mid
level low forming at the base of the trough as it takes on a
negative tilt Tue. The 00Z GFS continues that models tendency to
be too fast and too far north with the mid level and surface
system over the Central Plains and the Oh Valley Tue into Wed.

After that time, the evolution of the mid level system becomes
murkier, as short wave energy from eastern Canada drops into the
closed low/long wave trough over the eastern OH Valley during Wed.
The 12z ECMWF/ECMWF Ensemble mean seem slower than the consensus,
but this could be temporary as the mid level system evolves going
into Thu. For this reason, the 12z ECWMF remains in the
preference.


...Next Pacific trough reaching the West Coast Tue and Great Basin
Wed...
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Preference: Non 12Z CMC blend
Confidence: Average

Both the 00z NAM/GFS were close with the timing and evolution of
the long wave trough crosses CA and the Great Basin late Wed into
early Thu. In fact, only the 12z CMC is not tightly clustered with
placement of the closed mid level low over NV by 19/12z.


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

Hayes