Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1243 AM EDT Tue Apr 10 2018

Valid Apr 10/0000 UTC thru Apr 13/1200 UTC

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

00Z NAM/GFS evaluation with preliminary model preferences
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS initialization errors do not seem to degrade their short
range forecasts.


System carving out in the Rockies/Intermountain West Thu
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: ECMWF/UKMET blend; confidence average

The 12z Canadian is slower with the ridge/trough couplet moving
into the eastern Pacific/West Thursday night -- its usual bias. 
Meanwhile, the 00z GFS/00z NAM are quicker/broader with the
mid-level cyclone emerging into the Plains, which is notable in
their surface low latitude/progression.  As the flow pattern in
which the system is embedded is amplifying, a somewhat sharper and
slower position would normally be preferred -- this rules out the
NAM/GFS as too quick.  The 12z ECMWF/12z UKMET are closest to the
12z ECMWF/18z GEFS means so they appear reasonable -- a compromise
of the two is preferred with average confidence.


Northern Plains/Great Lakes/Northeast Low Wed/Thu
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-ECMWF blend; confidence average

The 12z ECMWF pumps up the ridge moving through the West/Plains
Wednesday and Thursday a bit more than the remainder of the
guidance -- an issue sometimes seen with the ECMWF.  Despite the
parent shortwave to the surface low being somewhat weaker on the
ECMWF than the other guidance, its surface low is farther north
instead of more southerly because of this amped ridge.  The
deterministic guidance fits nicely within the 12z global ensemble
guidance with the surface low position.  The 12z ECMWF appears to
have a convective/gridscale feedback bull's eye which eventually
gets the strength of the upper level system more on par with the
remainder of the guidance, but this appears to be at the cost of
its QPF pattern across MN.  Overall, believe a compromise of the
12z Canadian, 12z UKMET, 00z NAM, and 00z GFS appears best with
average confidence.  For more QPF details, see the WPC QPF
discussion.


Front moving through Michigan Wednesday
New England shortwave into Tuesday
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The guidance is in good agreement with these systems.  A
compromise of the 12z ECMWF, 12z Canadian, 12z UKMET, 00z GFS, and
00z NAM is preferred with above average confidence.


Shortwave moving through the Southeast Tuesday/early Wed
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM blend; confidence slightly above ave

The 00z NAM remains a deep outlier with this system.  Since it is
embedded within a flow pattern with broad wavelength, a broader
shortwave representation makes more sense.  A compromise of the
12z ECMWF, 12z Canadian, 12z UKMET, and 00z GFS is preferred with
above average confidence.


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

Roth