Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
232 AM EDT Sat Jul 21 2018

Valid Jul 21/0000 UTC thru Jul 24/1200 UTC

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

00Z GFS/NAM Evaluation with Preliminary Model Preferences
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The guidance shows good agreement with with system moving eastward
along the US/Canadian border and is within reason with the
amplified upper trough near the 85th meridian and its associated
surface lows.  A compromise of the available guidance (12z
Canadian, 12z ECMWF, 12z UKMET, 00z GFS, and 00z NAM) should work
out fine in most areas with above average confidence. 

With the low moving up the East coast into the Northeast, the
preferred solution would be closest to a compromise of the 00z NAM
and 12z ECMWF.  Confidence is no better than average here due to
remaining dispersion in the guidance and uncertainty of how much
latent heat would help deepen the potentially convective frontal
wave prior to its passing the NC/VA border (pulling away from the
Gulf Stream/warm Atlantic waters) prior to Saturday early
afternoon.

Roth