Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1239 PM EDT Fri Jun 08 2018

Valid Jun 08/1200 UTC thru Jun 12/0000 UTC

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

12Z Model Evaluation...with Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Upper trough crossing the Northeast today...
...Broader trough digging in by Saturday/Sunday...

Preference: General model blend
Confidence: Above average

The models agree in having one shortwave cross the Northeast
through today which will be amplifying a bit as it lifts northeast
across the Canadian maritimes on Saturday. However, there will be
additional shortwave energy dropping southeast from Quebec on
Sunday which will sharpen over especially northern New England.
The latest models are in good agreement with the evolution of
these systems, and thus a general model blend will be preferred.


...Vorts crossing the Northern Plains/Midwest today...
...Crossing the OH Valley and Mid-Atlantic this weekend...
...Frontal zone from the Midwest to the Mid-Atlantic...

Preference: Blend of the 12Z GFS and 00Z ECMWF
Confidence: Average

The guidance again takes a series of shortwave impulse across the
Northern Plains today and then off to the southeast including the
OH Valley and Mid-Atlantic region this weekend with some degree of
larger scale trough amplification expected. The 12Z NAM and 00Z
UKMET are both the most developed with the overall ejection of
shortwave energy out of the Midwest and across the OH Valley and
Mid-Atlantic region going through the weekend and early next week
which corresponds to a bit stronger surface low reflection along a
frontal zone draped across the region. The NAM and UKMET are
farther north with their respective low tracks, versus the 12Z
GFS, 00Z ECMWF and 00Z CMC which are all farther south and
relatively weaker with their wave activity. The CMC though is the
most progressive solution with its evolving upper trough. There is
better ensemble clustering/support is toward the GFS/ECMWF camp,
and a blend of these solutions will be preferred.


...Deep upper trough coming into the Northwest this weekend...
...Cold front sweeping out across the Plains by Monday...

Preference: Blend of the 12Z GFS, 00Z UKMET and 00Z ECMWF
Confidence: Slightly above average

The latest guidance strongly agrees in bringing a rather anomalous
trough in across the Northwest U.S. this weekend with pronounced
height falls and a strong cold front traversing the Great Basin
before then ejecting out across the Plains by Monday. There is
rather good agreement with the details of the height falls and
timing features involving the front as well, but the 12Z NAM does
appear a little too strong with its height falls across the
northern Rockies and adjacent areas of southwest Canada. The 00Z
CMC also appears perhaps a little slow with its trough evolution
by the end of the period. Overall, the best model clustering
resides with the 12Z GFS, 00Z UKMET and 00Z ECMWF, and so a blend
of these solutions will be preferred.


...Upper low/trough over the Southeast...

Preference: General model blend
Confidence: Above average

The models maintain a large scale weakness over the Southeast
through the weekend. Will prefer a general model blend once again.


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

Orrison