Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
327 PM EDT Fri May 24 2019

Valid May 24/1200 UTC thru May 28/0000 UTC

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

12Z Final Model Evaluation Including Preferences and Forecast
Confidence...
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...Overall CONUS Overview...
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Preference: General model blend
Confidence: Slightly above average

19Z Update: 12Z/24 Non-NCEP guidance remained generally in
alignment with the previous blend and NCEP suite through the
Memorial Day weekend. The only noticeable difference is in
northern stream jet energy across Southern Canada late in the
forecast period, as the ECMWF and UKMET both feature a more
intense jet maximum. However, at this time it produces little
difference in the overall synoptic regime or sensible weather, and
the significant differences remain tied to mesoscale features. The
preferred blend remains, but can now include the 12Z CMC which has
come into better agreement with timing of the shortwave across the
Southwest early Monday.

Previous Discussion:
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Mean synoptic pattern across the CONUS will generally remain
stagnant with an anomalously strong longwave trough across the
west supporting downstream ridging across the east. This pattern
will be one in which timing differences of mesoscale features
determine any small scale flow discrepancies.

With the deep trough becoming more amplified and closing off
across Southern California by day 2/3, pieces of shortwave energy
shedding eastward through the middle of the CONUS will create the
most robust convective potential and QPF placement variances, but
these are too small to be resolved on synoptic spatial and
temporal scales. This suggests that other than the 00Z/24 Canadian
which is anomalously fast with a potent shortwave lifting across
Baja and into the Southwest Sunday into Monday, the previous model
preferences are reasonable as the 12Z NCEP guidance remained in
good agreement with the 00Z Suite. The only noticeable change with
the 12Z NCEP models was an amplification in the GFS of the western
CONUS closed low Monday, but this puts it into better alignment
with the rest of the guidance. Minimal spread even into day 3 of
the spatial envelope of large scale features produces an above
average confidence in the model blend.


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

Weiss