Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
105 PM EDT Sun Jul 28 2019

Valid Jul 28/1200 UTC thru Aug 01/0000 UTC

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

12Z Model Evaluation including the NAM/GFS and preliminary
preferences
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Central and Eastern U.S...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Slightly above average

Models continue to show generally good consensus for all systems
across the CONUS during the short range period, and the 12Z NAM
and GFS solutions were in line with this consensus. With respect
to shortwave energy crossing the Upper Midwest/Great Lakes tonight
into Mon, models showed only minor timing/amplitude differences. A
deepening surface low associated with this system is expected to
move from south central Minnesota this evening to Lake Superior
and into Ontario by Monday. Model solutions were all very
well-clustered with respect to the track and timing of this
surface low. Solutions agree that this upper-level energy should
eventually close off into an upper low in the vicinity of James
Bay by Tue. A lingering area of upper-level energy across the
Southeast should eventually merge with additional energy from the
northern stream system, with all guidance showing an elongated
upper trough extending from the Great Lakes to the Southeast by
Tue-Wed. Models also handle these features similarly with only
minor differences. Farther west, models vary with respect to the
intensity of the upper ridge expected to remain anchored across
the Four Corners region, but a compromise or middle of the road
approach is preferred here. Given the overall good consensus, a
general model blend is recommended at this time.


...Pacific Northwest...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM blend
Confidence: Above average

An upper-level low is forecast by all guidance to dive southward
off the coast of British Columbia Mon-Wed. Solutions show some
variability on the timing and amplitude of this feature, with the
NAM being the one solution seeming to stray a bit from consensus,
bringing the upper low a bit farther east toward British Columbia,
and bringing lower heights a bit farther inland by Thu. Thus, will
recommend a non-NAM blend for this system.


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

Ryan