Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1221 AM EDT Thu Aug 02 2018

Valid Aug 02/0000 UTC thru Aug 05/1200 UTC

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

00Z Model Evaluation Including Preference and Forecast Confidence
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...Overall Synoptic Pattern across the CONUS...
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Preference: Non-NAM (less 00z GFS in Northeast)
Confidence: Slightly above average.

The narrow deep latitude trof across the eastern third of the
CONUS phases with a strong shortwave rotating around the southern
and western side of subtropical ridge before lifting up along the
Northeast coast into Sat.  The 00z NAM and GFS both are a bit
stronger in the mean synoptic trof and so deepen the surface wave
into SE Canada late Sat, outpacing the mean ensemble suite
(including the GEFS), so would favor a slower solution in mass,
toward the ECMWF/UKMET/CMC but a weaker GFS solution is still
tenable at lower weighting if desired.

A shortwave rounds the Southwestern ridge today into
tomorrow,before ejecting into the central Rockies Fri,  here the
00z GFS and NAM both slowed a bit to become better timed with the
12z UKMET/CMC while the 12z ECMWF lags a bit.  The wave will lift
north through MN, in advance of a positive tilt trof crossing the
Canadian Rockies into the Central Canada Fri/Sat.  The combination
of the two waves, will over-amplify with the 00z NAM, which
actually outpaces the remaining guidance; and while this trend was
noted with the 00z GFS (toward a deeper/compact solution), the 00z
GFS trended favorably slower toward the UKMET/CMC.  Here a Non-NAM
solution would be preferred. 

Off the Northwest coast, a large closed/stacked low will drop out
of the Gulf of AK by Sunday morning.  Here a general model blend
can be supported at above average confidence.

Overall, will favor a Non-NAM blend at slightly above average, but
would favor removal hedge away from the GFS in the
Northeast...with a bit more uncertainty/confidence in that area.

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

Gallina