Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
240 PM EDT Wed Mar 28 2018

Valid Mar 28/1200 UTC thru Apr 01/0000 UTC

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

12Z model evaluation...including model preferences and confidence
***NOTE: The 12Z ECMWF was not available for this issuance***
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...Southern stream trough over the southern Plains today...
...Surface low tracking from the lower Mississippi valley Thursday
morning to the Northeast Friday morning...
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Preference: Non-UKMET blend
Confidence: Slightly above average

A shortwave trough ejecting out across the southern Plains today
will continue to weaken as it moves east around the base of
stronger northern troughing/height falls focused over the northern
Plains and upper Mississippi Valley. The weakening remnant of this
energy will slingshot northeast up across the Ohio Valley and the
Northeast through early Friday along with a well-defined wave of
low pressure. The models are in good agreement with their mass
field details although the 12Z UKMET was a bit of a stronger
outlier and also tracks its low center a bit to the left of the
remaining model consensus. A non-UKMET blend will be preferred.


...Shortwave crossing the upper Mississippi Valley by Friday...
...Associated cold front crossing the region...
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Preference: General model blend
Confidence: Above average

The 12Z GFS is overall a little faster than the model consensus
with this feature, and the 12Z NAM just a tad slower. The non-NCEP
models all split the difference in between. Will recommend a
general model blend to resolve to he modest timing differences
seen with this.


...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: 12Z GFS
Confidence: Slightly above average

The models bring a shortwave in across the Northwest by Friday and
drop a surface low down across Montana. This energy will then
advance across the northern Plains and upper Mississippi Valley
late Friday and early Saturday. The 12Z NAM again is a bit of a
progressive outlier as the energy crosses the northern Plains. The
12Z UKMET is again the slowest solution as it has been for
multiple model cycles. The 00Z ECMWF tracks its low a bit north of
the 12Z GFS, but is also a bit north of the 12Z GEFS mean and the
00Z ECENS mean. The GFS has the best ensemble support and is
supported by the 12Z CMC, and thus the GFS will be preferred with
this system.


...Shortwave crossing the lower/middle Mississippi Valley Friday...
...Crossing the Ohio/Tennessee Valleys through Saturday...
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Preference: Non-CMC blend
Confidence: Slightly above average

The models are in good agreement with this progressive shortwave
until Saturday when the 12Z CMC edges a bit slower than the
otherwise well clustered model suite. Will prefer a non-CMC blend
at this time.


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

Orrison