Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
239 AM EDT Thu Mar 28 2019

Valid Mar 28/0000 UTC thru Mar 31/1200 UTC

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

00Z Model Evaluation With Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: Non-NAM blend...Central/Eastern U.S.
            Non-CMC blend...Western U.S.
Confidence: Slightly above average

The models are in good agreement in gradually weakening a deep
layer closed low offshore the West Coast over the next couple of
days. A portion of this closed low will separate off to the east
and inland across the northern Great Basin and northern Rockies by
Friday. This energy will then eject southeast across the central
Plains Friday night and get caught up into the base of an
amplifying northern stream trough over the Midwest through
Saturday. Although some trailing energy/troughing related to the
closed low is expected get left behind back toward the central
Rockies underneath a deep layer closed high center that drops
southeast from southwest Canada.

Overall, the 00Z NAM gets to be a bit deeper than the global
models with the northern stream trough evolution which ends up
supporting a bit stronger wave development along an attendant
frontal zone moving through the OH Valley by late Saturday and
toward the East Coast on Sunday. Will prefer a consensus of the
slightly less amplified global models which will include the
details of the surface wave and frontal timing.

By early Sunday, all of the guidance generally agrees with a weak
trough or closed low feature setting up over the Four Corners
region. The 00Z NAM/GFS/ECMWF solutions are a bit better defined
with the closed low, versus a somewhat weaker 00Z CMC. The 00Z
UKMET actually has trended a bit stronger and is closer to the
NAM/GFS/ECMWF camp. The latest GEFS and ECENS suites also tend to
favor a modestly stronger closed low feature over the region by
the end of the period, so will prefer a non-CMC blend with the
evolution of this feature. Additionally, a non-CMC blend will be
preferred with respect to a weak shortwave trough entering the
Pacific Northwest by Sunday. The CMC is notably slower than all of
the remaining guidance with this energy, and thus a multi-model
blend away from the CMC is recommended. This will also help to
resolve some of the modest spread seen with the depth of the
trough.


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

Orrison