Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1119 PM EST Thu Jan 17 2019

Valid Jan 18/0000 UTC thru Jan 21/1200 UTC

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

00Z Model Evaluation...with Preliminary Preferences
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A major winter storm will affect the central and eastern United
States as low pressure tracks from Colorado Friday morning to the
New England coast by Sunday. Frigid cold will develop after the
storm in the central and east, while weather in the West remains
active.

...Central and Eastern CONUS...
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Preference: Blend of the 00Z GFS / 12Z ECMWF

Energetic southern and northern stream troughs will eventually
phase, yielding a full latitude trough along the east coast by
Sunday. A well defined surface low will track from Colorado early
Friday to the New England coast by 12Z Sunday. The NAM, GFS, and
ECMWF are generally preferred as the 12Z Canadian becomes fast in
the northern stream over New England and the 12Z UKMET goes
severely out of phase from consensus upstream in the
Rockies/Plains. Of the preferred guidance, the GFS/ECMWF are a
little more preferred, whereas the NAM leans to the fast side of
the envelope both aloft and at the surface on Day 3, Sunday into
Monday.

Aloft there is some systematic difference between the GFS/GEFS and
the ECMWF/EC Ensemble, with the European being slower and more
closed off across New England on Day 3. There would seem to be
enough cold air to support the slower and more closed solution,
but given this is an ECMWF bias, and the GFS is not too far off
from this solution - especially at the surface - we recommend
blending the two models.

...Western CONUS...
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Preference: Blend of the 00Z GFS / 12Z ECMWF

The pattern over the West is a little more straight-forward, with
the gradual progression of an open, medium wavelength Pacific
trough into the West during Days 1-3. Such a system is usually
modeled fairly well, but the flow is energetic, and still with
some semblance of northern and southern stream components to
complicate matters. The 12Z UKMET was wildly out of phase with the
ensemble majority, and the 12Z Canadian as well as 00Z NAM
appeared too flat given the wavelength spacing and ensemble
consensus. Thus, the best options remaining appear to be the GFS
and ECMWF as they share a good deal of ensemble support.

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

Burke