Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1038 AM EST Mon Jan 21 2019

Valid Jan 21/1200 UTC thru Jan 25/0000 UTC

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

12z Model Evaluation Including Preferences and Forecast Confidence
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...Central US into Upper Midwest / Great Lakes Through Wednesday...
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Preference: Blend of the 12z NAM, 06z GFS, 00z UKMET, 00z ECENS
Mean
Confidence: Slightly Below Average

Current troughing digging through the interior West will shift
through the Four Corners region and into the Central US over the
next 24 hours. A surface low developing in the lee of the Rockies
Tuesday morning is expected to track toward the Upper Midwest and
Great Lakes region, bringing widespread precipitation including
mixed winter precipitation. Model agreement remains slightly below
average for this time frame, as there continues to be temporal
(and some spatial) differences in the deterministic solutions with
respect to the surface low track. The 12z NAM and 06z GFS remain
faster compared to most of the other guidance. The big outlier
with this system is the considerably slower ECMWF, which has the
surface low in southern Iowa (compared to northeast Wisconsin in
the NAM/UKMET, and southeast Wisconsin in the GFS). The past 3
cycles of the ECMWF have been slow, and all are slow than the
latest ECENS mean. The ECENS mean is in fact in line with the GFS
(and its mean) as well as to some degree the NAM/UKMET. For this
reason, the operational ECMWF is not preferred, but its ensemble
mean may not be a bad inclusion with the GFS/NAM/UKMET. The CMC,
while not spatially off, exhibits some of the temporal problems
the ECMWF has, but also is considerably stronger with its forcing
and thus its QPF solution across IA/MN/WI is an outlier. As such,
the WPC preference is for a blend of the GFS (GEFS mean), UKMET,
NAM, and ECENS mean.


...Pacific Northwest Tuesday Night into Wednesday...
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Preference: General model blend
Confidence: Average

Quick shortwave trough will drop through B.C. into the Pacific
Northwest Tuesday night into Wednesday on what will eventually
become a broad, longwave trough over the central/eastern US for
mid-week. Relatively good model agreement in the day 2-3 time
frame with this feature, especially at 500 mb. Minor spatial
differences are seen at the surface low, where the GFS/NAM are
further north as the low pushes into B.C. while the non-NCEP
models (UKMET/ECMWF) are south. All of the models then drop the
low southeast into the Pacific Northwest where it eventually
washes out.


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

Taylor