Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1055 AM EST Tue Jan 22 2019

Valid Jan 22/1200 UTC thru Jan 26/0000 UTC

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

12Z Model Evaluation Including Preferences and Forecast Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Developing Broad Cyclonic Flow Rockies and Eastward...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Slightly Above Average

Shortwave trough currently over the Four Corners region will
promote the development of a surface low in the central Plains
later today then track northeast toward the Upper Midwest and
lower Great Lakes. Moisture return ahead of it and strong dynamics
will lead to widespread precipitation both on the warm side and
cold side. Model agreement with the low track and timing is above
average with very good clustering in the deterministic and
ensemble guidance. The only deviation, which is relatively minor,
is the 00z CMC which takes the low further northwest and is also a
bit slower. A general model blend across the central/eastern US
will suffice through 36-48 hours.

Beyond 48 hours, a quick moving shortwave will drop through the
central US in the broad cyclonic flow Thursday night into Friday.
There are the usual timing/spatial differences seen in the
deterministic models this far out in time. By the end of the
forecast period, very broad/large scale troughing will encompass
much of the central/eastern US.


...Pacific Northwest...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of 12Z NAM/GFS
Confidence: Slightly Below Average

Several shortwave troughs will round the top of the upper level
ridge positioned just off the western US coast. The first in the
series will arrive Tuesday night across the Pacific NW followed by
another Friday. Overall model agreement is fair to slightly above
average with rather good clustering with the NCEP models. So for
now the WPC preference is for a general blend of the GFS and NAM.

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

Taylor