Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1247 PM EDT Tue Oct 30 2018

Valid Oct 30/1200 UTC thru Nov 03/0000 UTC

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

12Z NAM/GFS Model Evaluation...with Preliminary Preferences and
Confidence
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...Overall Pattern Across the CONUS...
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Preference: Non-NAM blend weighted toward 12Z GFS/00Z UKMET
Confidence: Average

A positively tilted trough over the western CONUS will swing east
through the next three days, becoming negatively tilted by 03/00Z.
 Model spread begins to increase after 01/00Z (Wednesday) as the
wave digs and takes on a neutral tilt over the Great Plains. The
00Z ECMWF deterministic and ensemble mean continue to be deeper
and stronger with the wave which results in slow QPF fields across
the southern US Wednesday night through Thursday. The best
agreement is with the 12Z GFS/00Z UKMET

In the West, model spread develops in the mass fields Thursday
night with the 00Z UKMET the most amplified with the approaching
trough.  However, from a precip perspective, there is good
consistency with a slug of moisture reaching Vancouver Island
Thursday before shifting south to western WA Friday. This QPF
consistency warrants general model blend is preference for the
Northwest.

Another digging wave on the back of the amplified trough should
lead to a clipper-like low track from the Canadian Prairies into
the Upper Midwest Friday. The 12Z NAM remains much stronger with
the wave aloft, and places the QPF farther northeast as compared
to the other deterministic models. The rest of the models are in
good consistency in mass fields and QPF, so a Non-NAM preference
is given to the Day 3 in the Upper Midwest.

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

Jackson