Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1252 PM EDT Tue May 15 2018

Valid May 15/1200 UTC thru May 19/0000 UTC

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

12Z NAM/GFS preferences and confidence intervals
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GFS/NAM initialization errors do not seem to degrade their short
range forecasts.


...Pair of closed lows impacting the West through Friday...
...Eventual cold front reaching the northern Plains Friday morning
with accompanying surface low/trough...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Model blend
Confidence: Slightly above average

A closed low currently over Nevada is expected to weaken toward
the north through Wednesday and Thursday while a second closed low
enters central California from the west. The 00Z CMC stands out
from the rest of the models, which are reasonably well clustered,
with the initial closed low being westward displaced across
Montana. The result at the surface into the northern Plains is a
more westward displaced trough axis/surface low as well.


...Broad upper level trough over the Great Lakes/Northeast...
...Pair of fronts affecting the Ohio
valley/Mid-Atlantic/Northeast...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Slightly above average

The models show similarly with this feature and broad agreement
with the frontal boundary(s) across the
Northeast/Mid-Atlantic/Ohio valley.


Closed low over the eastern Gulf of Mexico, slowly lifting north
while weakening through the end of the week...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non 00Z CMC blend
Confidence: Average

The 00Z CMC stands out with its mid-level low center displaced
south of the remaining consensus. While this placement is not an
outlier with respect the ensemble guidance, the lack of agreement
from the deterministic models is a concern. Given a less than
favorable track record for similar closed lows in the vicinity of
the Gulf Coast with the CMC, it will be discounted for the
preference. Detail differences remain with the non 0Z CMC models,
but they are in broad agreement on the larger scale details.


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

Otto