Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1249 PM EDT Thu Apr 04 2019

Valid Apr 04/1200 UTC thru Apr 08/0000 UTC

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

12Z Model Evaluation with Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Shortwave/surface low crossing the Ohio Valley Friday...
...Potential surface low developing along the Southeast coast Fri
night...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Average

Model solutions are reasonably well-clustered with respect to this
system through Fri as the shortwave and weak surface low move into
the Ohio Valley. Solutions have come more toward the idea shown
yesterday by a number of ECENS/CMCE members that another surface
low should develop along the Southeast/southern Mid-Atlantic coast
by Fri night/early Sat, with the NAM/GFS now also showing a weak
wave of low pressure moving northeast off the Mid-Atlantic coast
through Sat.


...Active Pacific upper-level jet reaching the West Coast with
series of embedded shortwaves...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Average

Model consensus has improved with respect to a number of
shortwaves/surface frontal systems expected to reach the West
Coast as part of a broad/strong Pacific upper-level jet
approaching the coast. The NAM/GFS have trended more amplified
compared to this time yesterday with a shortwave reaching the
Northwest early Sat. At this time, no significant outliers are
noted and a general model blend should smooth out any minor
timing/amplitude differences among solutions.


...Southern stream shortwave crossing the Southwest Fri and
reaching the central U.S. Sat/Sun...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: GFS/00Z ECMWF/00Z CMC blend
Confidence: Slightly below average

The NAM lowers heights a bit more quickly than the consensus of
other guidance across the central U.S. by Sat. Models also
continue to vary as to whether the system maintains a more open
wave type structure by Sun or closes off a compact upper low
across the Southern Plains. Models/ensemble members suggest the
potential for a couple surface lows across the central U.S. by
Sat-Sun, one crossing the Northern Plains/Upper Midwest and
another crossing the Southern Plains. At this time, a blend of the
GFS along with the 00Z ECMWF/CMC should depict a solution fairly
close to an ensemble-based consensus. Increasing spread on the
structure of the upper wave and the development/track of the
surface lows results in slightly below average confidence by the
end of the period.


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

Ryan