Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
113 AM EDT Tue Jun 18 2019

Valid Jun 18/0000 UTC thru Jun 21/1200 UTC

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

00Z Preliminary Model Evaluation...with Confidence and Preferences
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...Eastern and Central CONUS...
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Preference: Non-NAM Blend
Confidence: Slightly Above Average

Broad cyclonic flow will persist across the eastern 2/3 of the
CONUS through Wednesday before pattern amplification occurs in
response to troughing out west. Through day 2, the global suite is
in good agreement of the overall synoptic pattern, with
discrepancies only occurring with respect to shortwaves ejecting
through the flow. The CMC remains a bit fast with its translation
of these features, but not so much as previous runs, and within
the ensemble cluster at this time. Through day 2 a general model
blend should suffice.

However, by Thursday, the NAM rapidly deepens a shortwave lifting
through the Ohio Valley into a closed/negatively tilted trough.
This is not agreed upon by any other available guidance, and
continues the recent NAM trends of amplifying these shortwaves too
quickly and too strongly. For now, feel a non-NAM blend is the
best course beyond day 2 as other variations in small scale
features all fall within a reasonable spatial and temporal
envelope.


...Western CONUS...
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Preference: General Model Blend
Confidence: Average

Biggest challenge involves a closed low which will dig into the
PacNW Wed-Thu before stalling and shedding pieces of shortwave
energy around its base reinforcing a longwave trough in the West.
Overall model spread is minimal in thickness patterns and temporal
variation, although the exact evolution of the closed low varies
from model to model. A general model blend should be sufficient
for now, although timing and intensity differences of shortwaves
will affect heights and the QPF pattern across the West, so a
heavy weight of the ensemble means should limit this spread later
in the forecast period.


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

Weiss