Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1212 AM EDT Thu Oct 31 2019

Valid Oct 31/0000 UTC thru Nov 03/1200 UTC

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

00Z Model Evaluation with Preferences and Confidence
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Central to Eastern U.S. storm through Friday
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Preference: 12z GFS and 00z UKMET/ECMWF blend
Confidence: Slightly above average

The environmental pieces are coming together toward the fairly
rapid development of a strong surface cyclone in the Ohio Valley
sliding into the St. Lawrence Valley toward Fri with a strong,
progressive cold front pressing across the Eastern US.  The
overall guidance, while there are some small internal differences
particularly after 36hrs (CMC is north, and the 12z NAM is
slower), the agreement in the 12z GFS and 00z ECMWF/UKMET with
prior runs provides above average confidence in a GFS/ECMWF and
UKMET blend.

Next upper shortwave, press of cold air behind front over the
Plains/Midwest by this weekend
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Preference: 12z GFS and 00z ECWMF/CMC blend
Confidence: Above average

A northwest flow regime sets up across Canada, allowing for
another shot of cold air to press into the Northern
Plains/Boundary Waters region, supporting a surface wave and
frontal boundary clipping the Great Lakes by late Sat into Sunday.
 The 12z NAM, likely being a bit colder with its known bias, digs
a bit further south and is a bit stronger/deeper south with the
trof through the Ohio and Tennessee Valley by Sunday.  Similarly
the UKMET is deep in the upper TN valley/S Appalachians, though
this is better mass agreement with the GFS/ECMWF/CMC than the NAM;
this is a bit outside of the ensemble suite but could potentially
be added at lower weighting in a blend, if so desired.  However,
will favor a 12z GFS and 00z CMC/ECMWF blend at above average
confidence.

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

Gallina