Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
228 PM EST Sun Feb 03 2019

Valid Feb 03/1200 UTC thru Feb 07/0000 UTC

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

12Z Model Evaluation...with Final Preferences and Confidence
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...Low pressure off the Carolina Coast...
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Preference: Non-CMC 12Z Blend
Confidence: Slightly Above Average

A southern stream shortwave under the northern stream ridge shifts
east over the southeast CONUS, closing off after 04/00Z over
eastern NC.  The 12Z NAM/GFS are now similar with both the
mid-level low center and the surface low approaching the NC coast
overnight. The 12Z ECMWF shifted south a bit which brings it much
closer to the consensus of Non CMC 12Z guidance. The 12Z CMC has a
weaker surface ridge over the Mid-Atlantic and allows precip to
extend much farther northeast than consensus. Precipitation is
quite similar in two camps; the 12Z NAM/GFS and 12Z ECMWF/UKMET.
They are not that far apart, so a preference is given to these
four.


...Short wave and surface low Northern Rockies across the Upper
Great Lakes...
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Preference: 12Z GFS/UKMET
Confidence: Average

Minor disagreements persist with Day 1 timing and meridional
placement of the shortwave trough crossing the northern Plains
tonight into Monday with implications for wintry precipitation
forecasts. The 12Z ECMWF sped a little, but remains the slowest to
progress the mid-level trough axis while the 12Z GFS and CMC are
the most progressive and the 12Z NAM and CMC are the most
amplified. The 12Z UKMET is a good compromise among the global
guidance. The western extent of precipitation over northern ND is
in question with the slower ECMWF and stronger NAM having the
quarter inch QPF across northern ND, much farther west than other
guidance. The 12Z UKMET is a good compromise here with a nod to
the western flank while also being similar across the Great Lakes
to the global consensus. Will prefer the UKMET with the GFS as the
combination of most common attributes for this system.


...Closed mid-level low over CA/Opening over Great Basin...
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Preference: 12Z ECMWF/UKMET/GFS blend
Confidence: Average

The low shifting south from Vancouver Island this afternoon is
phasing with a shortwave low to its south which will draw the
phased low along the WA/OR coast Monday and shift into northern CA
Monday night. There is good agreement through 05/12Z except for
the 12Z CMC which is farther inland with the mid-level low center
and starts an early ejection which makes the CMC an outlier for
Days 2/3. Timing of the opening of this low and progression of the
positively tilted trough east over the western CONUS is decent
among the 12Z ECMWF/UKMET/GFS with the GFS the most progressive of
the three. Since the 12Z ECMWF is more progressive than the 00Z
run, the 12Z NAM is now a slow outlier. Good enough agreement with
the 12Z ECMWF/UKMET/GFS warrants having all three in the
preference.

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

Jackson