Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1142 PM EST Thu Jan 10 2019

Valid Jan 11/0000 UTC thru Jan 14/1200 UTC

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

00Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend
            -- Least weight on the 00Z GFS, 12Z CMC       
Confidence: Slightly above average

We are in the midst of a pattern amplification as the North
Pacific Jet undergoes an eastward extension. Models show a rex
block quickly forming in the next couple days over the West, with
greatest model uncertainties existing downstream from that (how
the wave consolidates and ejects east with associated
precipitation) and with the next trough approaching the West Coast
(how quickly the block is eroded).

Despite some continued model differences, there has been a general
convergence in QPF over the past couple model cycles. Over the
central and eastern US this is likely due to reduced model spread,
and along the West Coast this is likely due to good agreement on
the overall approach trajectory of the trough and terrain
enhancements dictating precipitation patterns. Therefore, the
preference is to lean toward a general model blend in the short
term portion of the forecast, and this corresponds well with the
preference in the medium range also.

Less weight was placed on the 00Z GFS. It still seems to be
ejecting the wave into the East faster than the other
deterministic models, and its only ensemble support is from some
of the GEFS members. It also continues to show a faster approach
for the trough on Sunday along the West Coast. Given the evolution
to a blocking pattern in the CONUS, the preference is for a slower
progression to synoptic features overall. The 12Z CMC also
received less weight, but for different reasons. It shows much
more trough amplification lagging the initial East Coast cyclone,
all the way back into the south-central US. It is near the outer
extent of model spread with its height pattern aloft, and is also
slower than all the other deterministic models with the approach
of the upper level low along the West Coast. These slower trends
can't be totally discounted given the aforementioned blocking
pattern, but given a lack of ensemble support it is receiving less
weight at this time.
 

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

Lamers