Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1255 PM EDT Thu Mar 12 2020
Valid Mar 12/1200 UTC thru Mar 16/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
12Z NAM/GFS Evaluation with Preliminary Preferences and Confidence
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...Northern stream trough tracking from the Upper Midwest toward
the Northeast through Friday...
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Preference: General model blend
Confidence: Slightly above average
The models show similarly with this system.
...Closed Low developing over Pacific NW Friday/Saturday...
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Preference: Non 12Z NAM blend
Confidence: Slightly above average
The 12Z NAM remains a bit of an outlier with respect to its closed
low dropping south across the Northwest U.S. The NAM is slightly
deeper at 700 mb offshore and less defined with a low level
convergence axis over west-central MT Saturday morning. The
differences in strength even out into Saturday night and Sunday
off of the West Coast, but the timing of the NAM lags the
remaining model consensus with only weak ensemble support. The
remaining non-12Z NAM guidance looks similar with the closed low
from 850-300 mb on Saturday and Sunday.
...Closed low tracking through the Southwest and weakening across
the Great Plains through Saturday...
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Preference: General model blend
Confidence: Slightly above average
Some relatively minor differences as the closed low ejects
eastward and weakens through the Great Plains. The 00Z CMC was
noted to be slower and a bit deeper with the remnant shortwave
trough axis, while the 12Z NAM was slightly faster. Overall, model
spread is small enough to allow for a general model blend.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Otto