Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
159 AM EST Wed Nov 21 2018

Valid Nov 21/0000 UTC thru Nov 24/1200 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
Confidence: Slightly above average

07z update: No significant differences noted with the rest of the
00z guidance coming in (ECMWF/CMC/UKMET). Will continue with
general model blend preference.

---previous discussion---
The current synoptic pattern across the CONUS features troughing
over the eastern US with ridging along the Intermountain West
while a couple of shortwave troughs approach the West Coast. At
the surface, a weak area of low pressure was located near Lake
Superior while another low was exiting the New England coast. High
pressure and benign weather extended for much of the rest of the
CONUS.

Through the forecast period, ridging aloft will move east toward
the central US while the Northeast US sees another digging
shortwave. The western trough will advance east as well, bringing
widespread precipitation to parts of California and the Pacific
Northwest.

In general, through 60 hours, the forecast guidance is in good
agreement with the large scale synoptic pattern. Across the West,
the guidance is in excellent agreement depicting the deep layer
ridge breaking down and the offshore trough advancing east and
well inland through Thanksgiving. This will set the stage for a
well-defined atmospheric river event to impact the Pacific
Northwest and especially northern CA.

Some differences are noted by Friday as a shortwave trough kicks
out into the southern Plains. The 00z NAM is considerably
stronger/deeper with the trough axis compared to the rest of the
guidance and becomes more negatively tilted by Friday night over
the mid-MS River Valley. At 250 mb, it's showing a 150+ kt jet
over Texas compared to the rest of the deterministic guidance
keeping the jet around 130 kt. Across the Pacific Northwest, the
12z UKMET is much stronger with shortwave energy moving in
Friday-Friday night as well.

With this in mind, the model preference across the CONUS was
leaned toward the 00z GFS, 12z ECMWF with some inclusion of the
00z NAM through 60 hours.


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

Taylor