Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1255 PM EDT Sat Jun 30 2018

Valid Jun 30/1200 UTC thru Jul 04/0000 UTC

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

12Z NAM/GFS evaluation...including preliminary preferences
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...Mean upper trough advancing from Montana/Wyoming to the Great
Lakes/accompanying cold front...
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Preference: 12Z GFS / 00Z ECMWF blend
Confidence: Average

Differences are greatest early in the forecast with the 00Z
UKMET/CMC faster and out of step with the agreeable 12Z NAM/GFS,
00Z ECMWF and ensemble means regarding a surface low forecast to
track through the upper Mississippi Valley on Sunday. However, the
effective cold front is quicker in the 12Z NAM through Sunday
evening but the models get into better alignment as the surface
front returns north as a warm front across the Mississippi Valley
into Tuesday. The 12Z GFS and 00Z ECMWF appear to align best
through Tuesday with this system.


...Westward moving mid/upper low/trough along the eastern/central
Gulf Coast...
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Preference: General model blend
Confidence: Average

The models show similarly with this system.


...Pronounced upper low/trough taking shape over the Pacific
Northwest by early next week...
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Preference: 12Z GFS, 00Z ECMWF, 00Z UKMET blend
Confidence: Slightly above average

The 12Z NAM remains fastest with the upper trough, related cold
front and surface low reaching South Dakota Tuesday morning. A 12Z
GFS, 00Z ECMWF and 00Z UKMET blend agrees well with the middle
road of the deterministic/ensemble guidance while also considering
minor trends to be faster compared to yesterday.


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

Otto