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The Weather Prediction Center

Model Diagnostic Discussion

[Abbreviations and acronyms used in this product]
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Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1214 PM EDT Thu Jul 19 2018

Valid Jul 19/1200 UTC thru Jul 23/0000 UTC

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

12Z model preferences and confidence intervals
Preference: UKMET/ECMWF/GFS/Canadian blend
Confidence: Above average

Low in Midwest/Ohio Valley...Shortwave/sfc low lifting along the
East Coast front...
Preference: 12z GFS and 00z ECMWF/UKMET blend
Confidence: Slightly above average

Run to run ensemble trends show a consolidation of solutions with
the closed low over the Midwest into Ohio valley, though toward
midday Sunday the 00z CMC remains deeper and concentric while the
remaining guidance is filling a bit.  The majority of spread
remains with the shortwave and associated surface wave lifting out
of the Southeast on Fri along the coast and hooking back west into
New England by Sunday morning, with the CMC out of is
also west of the clustering.  However, here the 12z NAM is also
very strong but most progressive.  The 12z GFS shifted a bit
slower and deeper, and while a still a bit west and weaker than
the remaining guidance, it appears fairly solid to the overall
best clustering.  The 00z UKMET may be a bit deep with this system
too, but if blended with the 12z GFS and ECMWF this will work out
well overall in a slightly above average confidence blend.

System skirting north of US/Canadian border
Preference: 12z GFS and 00z ECMWF/CMC blend
Confidence: Slightly above average

Closed low drops into Southern BC late Fri and elongates in a
positive tilt into the Pacific NW with fairly good agreement. 
Spread increases as the wave lifts Northeast into central Canada
with a surface wave and trailing frontal zone through the northern
tier of the US into Sun.  Here the 12z NAM winds up/consolidates a
bit south, along with the 00z UKMET and become progressive late
Sun with a further southeast surface reflection and faster front
in MT/Dakotas.  This is away from the trends/ensemble suite, so
would favor a 12z GFS and 00z ECMWF/CMC blend for this system at
slightly above average confidence.

Model trends at
500 mb forecasts at


Last Updated: 1214 PM EDT Thu Jul 19 2018