Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
334 PM EDT Tue Aug 20 2019

Valid Aug 20/1200 UTC thru Aug 24/0000 UTC

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

12Z Model Evaluation...Including Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: General deterministic model blend
Confidence: Average

...19Z Update...
The 12Z ECMWF is now the most amplified with the trough in the
eastern U.S. on Friday/Day 3. This pushes precip farther south and
a bit away from the 12Z consensus. However, given the
uncertainties associated with the movement of the cold front over
the central/eastern U.S., a general model blend is still
recommended.

...Previous Discussion...
Guidance is in generally good agreement on the main synoptic
features through Thursday which are the low over northern Ontario
swinging across Quebec and the progressive trough from a low
moving into southeast Alaska tonight that shifts across the
Canadian Prairies and northwest U.S. as flow becomes zonal over
the Pacific Northwest and southwest Canada to end the work week.
Timing and magnitude differences grow large on Day 3 with the
orientation of the trough over the Canadian Prairies into the
northern Great Plains and the low approaching Labrador and
associated trough crossing the northeastern U.S.

Shortwave activity along the cold front over the central and
eastern U.S. has understandable variability though precipitation
from deterministic guidance is in good agreement outside of the
12Z NAM on Day 3 which is much more robust over northern MO.
Therefore a general model blend is recommended with a caution of
the 12Z NAM on Day 3.

A trough of tropical origins shifts north across the western Gulf
of Mexico with potentially heavy precip on the northern end of the
trough reaching the Louisiana coast on Friday. A general model
blend is suggested with this feature.

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

Jackson