Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
324 AM EDT Fri Apr 26 2019

Valid Apr 26/0000 UTC thru Apr 29/1200 UTC

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

00Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend weighted toward GFS/NAM/UKMET
Confidence: Slightly above average

07z update: With the rest of the 00z guidance now available, model
mass fields are in relatively good agreement through the period.
No significant changes noted and the original preference for a
general model blend with more weight toward the GFS/NAM/UKMET
remains.

---previous discussion---
Fairly active northern stream energy will be found through the
next 3 days with a parade of shortwaves moving through the flow.
The first, currently a shortwave trough moving through the Ohio
Valley, will phase with additional energy and take on a negative
tilt over the Northeast US Friday night and Saturday. A faster
progression of this system is favored, given the upstream energy
quickly moving in its wake. This setup favors the faster
GFS/NAM/UKMET solutions, while the ECMWF has been slower to
evolve.

The next system is a very compact shortwave trough moving through
the central Plains and Upper Midwest on Saturday. A tight low
pressure system with strong frontogenetic forcing will bring a
swath of QPF to the Upper Midwest. Here, model consensus is fairly
good with the surface low position and strength as it skirts
across the region. The GFS looks to be a touch on the fast side
while the UKMET and ECMWF is on the slower end of the model
envelope, but for the most part the large scale mass fields are in
good agreement and a general model blend is preferred. The speed
differences noted in the deterministic guidance does affect the
QPF distribution, but with a general model blend some of that
should be minimized.

Finally, another stronger shortwave trough pushes onshore the
Pacific Northwest and moves into the northern Rockies by the end
of Day 3. The UKMET/NAM are the stronger solutions, closing off
the shortwave over North Dakota by the end of Day 3. Meanwhile,
the CMC and to some degree the ECMWF are slower and flatter,
though not too different from the GFS solution. All of the models
indicate another strong low pressure developing in Montana toward
the end of the period as well.


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

Taylor