Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
331 PM EDT Thu Mar 28 2019

Valid Mar 28/1200 UTC thru Apr 01/0000 UTC

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

12Z NAM/GFS Model Evaluation With Initial Preferences and
Confidence
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...Overall Pattern Across the CONUS...
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Preference: General Model blend...Days 1/2
            Non-GFS/NAM blend...Day 3 Northeastern U.S.
            Non-ECMWF blend...Day 3 Southwestern U.S.
Confidence: Slightly above average

The models are in good agreement in gradually weakening a deep
layer closed low offshore the West Coast into Friday. A portion of
this closed low will continue to shift east from California across
the northern Great Basin and northern Rockies to the Midwest
through Friday night and get caught up into the base of an
amplifying northern stream trough over the Midwest through
Saturday. A secondary shortwave from the closed low will stall
over the central Rockies underneath a deep layer closed high
center that drops southeast from southwest Canada Saturday night
and Sunday.

The main issue among global guidance is the 12Z GFS/06Z GEFS which
remain too progressive despite slowing from the 06Z run. This
affects the precip pattern over the eastern, and particularly
northeastern CONUS from Day 2 to Day 3. While the precipitation
coverage pattern is similar with the 12Z NAM, the northern stream
trough remains deeper than the global models 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. This results in a colder/snowier
solution which is an outlier. Will prefer a consensus of the
slightly less amplified/progressive global models which is the 00Z
ECMWF/UKMET/CMC. Will note that changes are likely with the 12Z
run of these models.

By early Sunday, guidance generally agrees with a weak trough or
closed low feature setting up over the Four Corners region. The
00Z ECMWF operational is the farthest south of the global models
and feature more precip for NM than CO on Day 3 while the ECENS
mean has more precip over the San Juan Mountains of CO. Therefore,
a non-operational 00Z ECMWF solution is recommended.


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

Jackson