Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
104 PM EDT Fri Mar 29 2019

Valid Mar 29/1200 UTC thru Apr 02/0000 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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...Central Plains...Midwest...to Northeast...
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Preference: Non-GFS/NAM blend
Confidence: Slightly above average

A southern stream shortwave ejecting east across the Intermountain
West today will cross the Central Plains tonight and begin to
interact with a northern stream trough that will cross the Great
Lakes, OH Valley and Northeast tonight through Sunday night.
 
Overall, the models show rather good agreement with the large
scale evolution of the northern stream trough evolution, but the
12Z NAM remains the most amplified/coldest and the 12Z GFS remains
the most progressive with the surface low moving up the St.
Lawrence Valley Saturday night. More ensemble support remains for
a more progressive solution than the deeper NAM and less
progressive than the GFS, so will prefer a non-GFS/NAM consensus
with the larger scale trough, front, surface wave, and resultant
QPF.

...Four Corners to Texas...
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Preference: Non CMC/ECWMF blend...Western U.S.
Confidence: Average

A secondary shortwave moving east from the West Coast behind the
initial will stall over the Four Corners area into Sunday
underneath a deep layer closed high center that drops southeast
from southwest Canada. This trough then ejects southeast to TX
through Monday.

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 CMC solution is a bit stronger with this cycle,
but is still overall the weakest and fastest solution. Every other
model including the 12Z NAM/GFS solutions and the 00Z UKMET/ECMWF
solutions support a relatively deeper trough and possibly a weak
closed low dropping south with time across the Four Corners
region. However, the 00Z ECMWF/ECENS remains farther south than
the rest of the guidance and should be limited in its inclusion.
The slower/more closed 00Z ECMWF then allows more Day 3 precip
over TX which is an outlier. Therefore the preference is for the
similar 12Z NAM/GFS/00Z UKMET.

...Pacific Northwest...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 06Z GEFS/00Z ECENS blend
Confidence: Average

Deterministic runs are varied for the Day 3 trough/low approaching
the CA/OR coast Monday. However, the mean troughs in the 06Z GEFS
and 00Z ECENS are similar enough to warrant a preference for areal
coverage of QPF.


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

Jackson