Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
321 PM EDT Fri Mar 29 2019

Valid Mar 29/1200 UTC thru Apr 02/0000 UTC

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

12Z Model Evaluation With Preferences and Confidence
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...Central Plains...Midwest...Northeast interacting troughs
Tonight through Sunday night...
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Preference: Non-GFS/NAM blend
Confidence: Slightly above average

A southern stream shortwave ejecting east across the Intermountain
West today will cross the Central Plains tonight and begin to
interact with a northern stream trough that will cross the Great
Lakes tonight through Sunday and the Northeast Sunday through
Sunday night.
 
Overall, the models show rather good agreement with the large
scale evolution of the northern stream trough, but the 12Z NAM
remains the most amplified/coldest and the 12Z GFS remains the
most progressive with the surface low moving up the St. Lawrence
Valley Saturday night. More ensemble support remains for a more
progressive solution than the deeper NAM and less progressive than
the GFS, so will prefer a non-GFS/NAM consensus with the larger
scale trough, front, surface wave, and resultant QPF.

...Four Corners to Texas wave Saturday night through Monday...
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Preference: Non CMC blend
Confidence: Average

A secondary shortwave moving east from the West Coast behind the
initial wave will stall over the Four Corners area into Sunday
underneath a closed high center that drops southeast from
southwest Canada. This trough then ejects southeast to TX through
Monday.

By early Sunday, all of the guidance generally agrees with a weak
trough or closed low feature setting up over the Four Corners
region. The 12Z CMC solution remains farther north and open,
making it the weakest and fastest solution. The 12Z
NAM/GFS/ECMWF/UKMET solutions support a weak closed low dropping
southeast across UT/CO. Timing with the 12Z ECMWF is fast
enough/farther north enough to be included in the blend.

...Trough/Low approaching Pacific Northwest Monday...
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Preference: 12Z GEFS/00Z ECENS blend
Confidence: Average

Deterministic 12Z runs became less varied for the Day 3 trough/low
approaching the CA/OR coast Monday. The UKMET is notably deeper
and farther north than the consensus. However, the mean troughs in
the 12Z GEFS and 00Z ECENS are similar enough to warrant a
preference for QPF area with QPF magnitude from a non-UKMET blend.


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

Jackson