Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
232 AM EDT Fri Aug 16 2019

Valid Aug 16/0000 UTC thru Aug 19/1200 UTC

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

00Z Model Evaluation...Including Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of the 00Z GFS/ECMWF
Confidence: Slightly above average

The upper-level pattern starts off with modest ridging across the
Southwest and broad northwesterly flow to its north and downstream
across the northern Plains and Midwest, leading to broad troughing
across the eastern half of the nation. The ridge over the
Southwest will continue to weekend on Friday and Saturday as
stronger northern stream troughing digs south through southwest to
south-central Canada and across the northern Rockies and northern
Plains region. On Sunday, the troughing will pivot across the
Midwest and Great Lakes region, but will begin to retreat a bit
farther north which will allow an elongated subtropical ridge to
be focuses across the central and southern U.S. and rather strong
zonal flow from the Northwest to the Northeast associated with the
westerlies up across the northern tier of the nation.

Anomalous moisture will remain in place ahead of a slow moving
front which will extend from the Mid-Atlantic region to the Gulf
Coast, while impulses in northwest flow aloft keep the central
Plains to the Midwest active with multiple rounds of organized
convection. There is broad agreement among the global models with
the synoptic scale features across these areas, but the 00Z NAM in
general appears to be a tad too amplified with its convectively
enhanced vort energy crossing areas of the lower MO and middle MS
Valleys through Friday and Saturday.

Across the Southeast and eastern Gulf Coast region, the guidance
continues to hint at a weak area of low 
pressure developing along the aforementioned front, and the
guidance agrees in lifting a weak area of low pressure up along
the front and across the southern Mid-Atlantic through Friday
night and then offshore the East Coast on Saturday. A second area
of low pressure is also being forecast by the guidance to evolve
near the coastal plain of the Carolinas Sunday night and Monday.
The 00Z UKMET is a stronger outlier with this system which also
corresponds to a much wetter solution over southeast NC.
 
The height fall evolution across southwest to south-central Canada
is better resolved it would appear as compared to 24 hours, but
the 00Z NAM appears to be a tad too strong with both of its closed
lows with one impacting Saskatchewan and Manitoba, and one digging
south across British Columbia. There is notably better support
from the GEFS mean and ECENS mean for the non-NAM deterministic
suite of guidance and particularly the 00Z GFS/ECMWF solutions.
Given the concerns with the NAM and UKMET locally across the CONUS
and over central and southern areas of Canada, a blend of the GFS
and ECMWF will be preferred at this point.


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

Orrison