Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1145 AM EST Thu Jan 03 2019

Valid Jan 03/1200 UTC thru Jan 07/0000 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...across the Eastern U.S.
            00Z ECMWF/ECENS mean blend...Central/Western U.S.
Confidence: Above average...across the Eastern U.S.
            Below average...across the Central/Western U.S.

Distinct northern and southern stream energy will be progressive
across the CONUS through the forecast period. One system in the
southern stream will be a closed low which is currently moving
across Texas along with an associated surface low. The system will
track across the Southeast U.S. and then lift through the
Mid-Atlantic region before going offshore. The guidance is in good
agreement with this system through 48 hours, but thereafter the
00Z UKMET begins to outrun the model consensus, with the 00Z ECMWF
lagging it just a tad. The 12Z NAM/GFS solutions are very close to
the model consensus.

Across the Western U.S., there will be a combination of northern
and southern stream energy impacting the region. Initially, an
atmospheric river will push into western and northern WA through
tonight and early Friday, and will bring locally heavy
precipitation to the favored upslope regions. The latest guidance
is in very good agreement with this system. On the heels of this
system though will be another large scale trough and deep low
center that will approach the West Coast by Saturday with an
emphasis on northern CA. This energy will then lift across the
Intermountain West on Sunday. The GFS remains faster compared to
the NAM and also the non-NCEP solutions. However, the NAM takes
its surface low farthest north along the West Coast, with the CMC
farthest south and also the slowest. The ECMWF and UKMET are
closest to the model consensus with this system. Then finally,
there will be another shortwave and potential low center
approaching western Oregon by late Sunday, which only the GFS and
CMC seem to strongly emphasize. The remaining guidance is notably
flatter with the energy and there tends to be more ensemble
support for the flatter solution at this point.

So for this cycle, the WPC preference will be for a general model
blend for the Eastern U.S. through the period. Across the
Central/Western U.S., a solution toward a blend of the ECMWF and
ECENS mean will be preferred.

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

Orrison