Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1149 PM EST Sat Nov 24 2018

Valid Nov 25/0000 UTC thru Nov 28/1200 UTC

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

00Z NAM/GFS Evaluation...with Preliminary Preferences and
Confidence
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...Overall pattern across the CONUS...
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Preference: 00Z GFS/00Z NAM/12Z ECMWF blend
Confidence: Slightly above average

The upper pattern starts off with two potent shortwaves, one
exiting negatively tilted shortwave near New England and the other
amplifying into the central Plains. The Plains shortwave will
track to the Northeast on Monday as a large closed low develops
over the Great Lakes region through Tuesday morning. Meanwhile out
West, upper level ridging along the West Coast will translate east
as broad longwave troughing moves into the western U.S. through
mid-week.

Regarding a developing coastal low near New England early Sunday
morning, only the 12Z UKMET stands out with a position closer to
the coast while the remaining deterministic/ensemble guidance is
in good agreement.

Across the Plains/Midwest, there is a relatively small but
significant difference between the 00Z NAM/GFS and the 12Z
ECMWF/UKMET/CMC with the 00Z NAM/GFS showing a closed low slightly
west of the more open 12Z ECMWF/UKMET/CMC. Given the short term
forecast (Day 1), and ensemble support, there should be more
weight toward the newly initialized NAM/GFS idea through early
Monday. A secondary low forms near the New England coast with
relatively good agreement between the 00Z NAM/GFS and 12Z
ECMWF...in line with tight ensemble clustering.

Across the West, some timing differences exist with a cold front
moving down the CA coast on Tuesday/Tuesday night. Trends are
inconclusive as to faster or slower but the GEFS/ECMWF means
support a middle ground approach for now.


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

Otto