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

Valid Jan 22/0000 UTC thru Jan 25/1200 UTC

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

Final 00Z Model Evaluation
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...Developing Broad Cyclonic Flow Rockies and Eastward...
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Preference: Blend of 00Z GFS/EMCWF/UKMET
Confidence: Slightly Above Average

A cold front and pronounced shortwave trough will push out of the
Rockies and toward the East Coast through Thursday, followed by a
northern stream arctic intrusion that will carve out a deep and
broad scale cyclonic flow regime by Friday morning. Models have
been struggling from run to run in depicting the amplitude of a
frontal wave and brief mid level closed low over the central
Plains beginning Tuesday. This led us to trust the shorter term
trends seen in the 00Z NAM/GFS with the system now fully in the
upper air network. These trends were backed up by a shift in the
other global guidance as well, so this bolsters confidence as the
full 00Z global model suite strongly converged on a solution. The
NAM looks a little squirrelly, with suddenly very cold heights
over the southern High Plains early Day 1, and then an odd
eastward shove on the surface low over eastern Canada by Days 2/3
- so we will not have the NAM in our preference, but it could be
useful in some areas. Likewise, we omit the Canadian model whose
surface progression is a little slower than consensus, but the
trend between the 12Z and 00Z runs was consistent with other
guidance - particularly the Day 1 period and development of the
sharper wave in the central Plains.


...Pacific Northwest...
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Preference: Blend of 00Z NAM/GFS
Confidence: Slightly Below Average

Numerous low amplitude shortwave troughs are set to cut across the
top of a mean ridge position off the West Coast, and move into the
Pacific Northwest the next few days. The shortwave details carry a
good deal of uncertainty, but model and ensemble clustering as
well as run to run continuity have generally favored the NCEP
guidance relative to the ECMWF the past few cycles.

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

Burke