Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
147 PM EST Mon Feb 05 2018

Valid Feb 05/1200 UTC through Feb 09/0000 UTC


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

12Z Model Preferences with Confidence Intervals
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Initialization errors in the NAM/GFS do not seem to degrade their
short range forecasts.


Upper trough weakening as it moves out of the Southwest
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM compromise; Confidence above average

The 12z NAM is a little more amplified aloft with the upper trough
in the Southwest which allows it to drag eastward into Texas as a
stronger feature on Wednesday.  Overall, a broad trough exists
over North American with a strong mid-level reflection of the
Polar Vortex across northwest Quebec.  This should force the
system to eject out relatively flat, eliminating the NAM from
consideration.  This is important in the model instability fields
across TX as well as QPF pattern across the southern Plains, lower
MS valley, and Mid-South.  See the QPF discussion for more details
on the precipitation forecast.  A compromise of the 12z Canadian,
12z ECMWF, 12z GFS and 12z UKMET is advised with above average
confidence.


Shortwave moving towards the Northwest Thursday
Boundary in the central Plains/Midwest Thursday
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-ECMWF compromise; Confidence slightly above average

The 12z ECMWF became a bit slower with this energy rounding the
top of the eastern Pacific ridge, which combined with a slightly
slower shortwave moving down through southern Canada leads to
small differences in the surface boundary stretching from the
central Plains into the Midwest Thursday.  Normally, shortwaves
speed up when they go through the supergeostrophic flow over the
top of the ridge, so believe the ECMWF is too slow with that
system.  Considering the northerly flow through central Canada, it
could be too slow with the northern stream shortwave as well.  A
compromise of the 12z Canadian, 12z UKMET, 12z GFS and 12z NAM is
preferred with slightly above average confidence.


Shortwave moving across New England Tuesday
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The guidance is within reason with this system.  A compromise of
the 12z Canadian, 12z ECMWF, 12z UKMET, 12z NAM, and 12z GFS
should work out well with above average confidence.


Roth

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