Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
124 AM EDT Wed Mar 28 2018

Valid Mar 28/0000 UTC thru Mar 31/1200 UTC

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

00Z NAM/GFS evaluation...including preliminary preferences
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...Southern stream trough over the New Mexico advancing east...
...Surface low tracking from the lower Mississippi valley Thursday
morning to the Northeast Friday morning...
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Preference: Blend of the 12Z UKMET, 12Z ECMWF and 00Z GFS
Confidence: Slightly below average

The 00Z NAM is still on the faster side of the model spread with
the ejecting shortwave through the Ohio valley on Thursday. The
ECMWF trended slower with this feature and is nearer to the GFS
compared to yesterday, but the 00Z GFS remains a slower than the
12Z ECMWF with the ensembles (GEFS and ECENS) reflecting their
parent models. The ensemble scatter low surface plots support a
broad blend of the 00Z GFS, 12Z ECMWF and 12Z UKMET with future
wobbles expected.


...Shortwave digging across the north-central U.S. today...
...Surface low tracking through Ontario today with trailing cold
front across the Great Lakes...
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Preference: General model blend
Confidence: Above average

The models show similarly with this system.


...Shortwave moving over the Northwest by Friday...
...Surface low dropping down across Montana and nearing the upper
Mississippi Valley Saturday morning...
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Preference: near the 00Z NAM
Confidence: Average

The models bring a shortwave in across the Northwest by Friday and
drop a surface low down across Montana. The 12Z UKMET is the
slowest solution, with the 00Z NAM, 00Z GFS, 12Z CMC and 12Z ECMWF
all faster. There has been a flip in model timing, where the
slower models from yesterday are now faster and vice versa. The
ensemble spaghetti height plots at 500 mb show modest spread in
timing and a low amplitude shortwave. Ensemble scatter low plots
split the difference between the farther south 00Z GFS surface low
track and the farther north 12Z ECMWF. The 00Z NAM currently
splits this difference and lies in the middle of the deterministic
and ensemble spread.

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

Otto