Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1227 PM EDT Mon Apr 29 2019

Valid Apr 29/1200 UTC thru May 03/0000 UTC

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

12Z Model Evaluation w/Preferences & Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS initialization issues appear small and do not seem to
degrade their short range forecasts.

...Frontal System crossing the mid Ms Valley to the Great Lakes
and Ohio Valley mid week...
Preference: Non-NAM blend (blend ECMWF/UKMET/GFS)
Confidence: Slightly above average

The 12z NAM was most assertive in developing a wave along the
front in MI 12z Wed and then lowering heights/surface pressure
along the trailing cold front into the Ohio Valley on Thu.
The GFS/ECMWF/UKMET/Canadian have less in the way of
height/pressure falls Wed-Thu.  With the strong anticyclone off
the southeast coast set to act as a block to eastward frontal
progression...prefer the slower UKMET/ECMWF/GFS/Canadian in the
Great Lakes/Ohio Valley/mid-lower MS Valley.


...Northern Plains/Upper MS Valley/Upper Great Lakes...
Preference: Blend of ECMWF/UKMET/09z SREF Mean
Confidence: Slightly above average

The 06-12z GFS are slower in moving the 700 mb wave out of the
northern Plains and MN into southern Canada with the
ECMWF/UKMET/Canadian/NAM all faster.  The faster solutions looks
more likely with the developing western US trough likely to act as
a kicker to eject the northern Plains/upper MS Valley system.

...Frontal system crossing the Great Basin and central to southern
Rockies/southern Plains...
Preference: Blend of NAM/ECMWF/GFS/UKMET
Confidence: Slightly above average

The models have converged with the forecast with considerable
overlap of the wavy frontal system crossing NV/UT/CO/southern
Plains tonight through Tuesday.  This overlap lends itself to
using a model consensus to resolve detail differences among the
model solutions.

...Frontal system developing and crossing Northern Rockies Wed
night and high northern Plains Thu...
Preference: Blend of NAM/ECMWF/GFS/UKMET
Confidence: Slightly above average

The models agree on developing a 700-500 mb trough in southwest
Canada into the northwest US Wed night and Thu, which drives a
cold front from the northern Rockies across the northern Plains. 
Development of low pressure north of MT is possible, with slight
timing/location differences typical of a day 3 forecast.  With a
loose clustering of solutions, a blend of the models is
recommended until clustering increases.

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

Petersen