Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1147 PM EST Tue Feb 05 2019

Valid Feb 06/0000 UTC thru Feb 09/1200 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, 12Z ECMWF, 12Z UKMET blend
Confidence: Average

The overall 500 mb pattern across the lower 48 will feature mean
ridging over the Gulf of Mexico to offshore Florida and mean
troughing over the western U.S. Two surface lows will impact
locations east of the Rockies over the next couple of days, the
first being relatively weak near the Ohio Valley today and the
second, much stronger low, to affect the Great Lakes region on
Thursday with the ejection of a large upper trough currently
located over the West. Across the West coast, two closed lows are
expected to impact the region from Thursday to Saturday morning.

Both the 00Z NAM and 12Z CMC are a bit faster and north of the
better deterministic and ensemble clustering regarding both
surface lows east of the Rockies. The first low is expected to
track through the Ohio Valley today and reach the southern New
England coast around mid-day Thursday. A 00Z GFS, 12Z ECMWF, 12Z
UKMET blend is preferred for this first low. For the second and
stronger surface low to impact the Great Lakes region, the 00Z
GFS, 12Z ECMWF and 12Z UKMET again show good agreement but the 12Z
ECMWF is the slowest of the three. The 12Z ECMWF mean is a hair
faster than the 12Z deterministic ECMWF while ensemble low
clustering supports the middle ground of the 00Z GFS, 12Z ECMWF
and 12Z UKMET.

Across the West Coast, a closed low is forecast to drop southward
just offshore Thursday and Friday before entering California and
becoming an open wave. The 00Z NAM is in the minority of
ECMWF/CMC/GEFS ensemble members with a slower and more offshore
track. A non 00Z NAM blend looks best for this system.

Another closed low is forecast to near the Pacific Northwest by
Saturday morning, with all of the latest deterministic models,
except for the faster and farther westward tracking 12Z CMC. A non
12Z CMC blend is recommended for the Pacific Northwest closed low
system.

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

Otto