Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
243 PM EDT Wed Oct 17 2018

Valid Oct 17/1200 UTC thru Oct 21/0000 UTC

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

12Z Model Evaluation...with latest preferences and confidence

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...Overall Pattern Across the CONUS
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Preference: General model blend
Confidence: Above average

19z Update: The 12z ECMWF did not deviate significantly from
previous runs and compared to the 12z GFS with respect to the 500
mb heights. The 12z CMC/UKMET were reasonably similar through day
2, but begin to show some differences in timing by day 3,
particularly with the strong shortwave trough moving through the
Great Lakes region. With the closed low expected to form by day 3
off the coast of California, the models are fairly similar with
its placement.

---Previous Discussion---
A longwave trough will continue across the central/eastern US
through the weekend. A closed low currently over the Four Corners
region will open up, lift northeast, and become absorbed in
northern stream energy carving out a reinforcing trough. The
Intermountain West will remain under the influence of a ridge
while troughing continues across the east. At the surface, a
couple of fronts will pass through the central/eastern US,
bringing reinforcing shots of cooler air followed by sprawling
high pressure.

The 12z GFS and NAM were largely in good agreement with the
remaining deterministic and ensemble guidance through Friday. The
12z GFS trended slower with the shortwave trough coming across the
northern US and Great Lakes region Friday/Saturday and is now
slightly slower than the 06z GEFS mean. This appears to have
little difference at the surface with the frontal passage however.
Otherwise, the NAM is aligned well through Day 2 but has some
subtle timing/placement differences for Day 3 (Saturday).

Given the good agreement and little variability through Day 3, a
general model blend will be preferred for this period.

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

Taylor