Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
244 PM EDT Mon Mar 26 2018

Valid Mar 26/1200 UTC thru Mar 30/0000 UTC

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

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

***Due to ongoing NCEP data issues model data in NAWIPS were
unavailable. 12Z guidance were evaluated in AWIPS2. The UKMET is
only available through 36 hours.***

...Southern stream portion of trough in the West, moving to the
Plains by Wednesday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 12Z GFS/NAM/ECMWF blend
Confidence: Above Average

Generally good agreement for the upper low/positively tilted
trough over the desert SW as it fills crossing the four corners
region through Tuesday then as it becomes neutrally tilted and in
line with the northern stream down the center of the CONUS on
Wednesday. A 12Z GFS/NAM/UKMET/ECMWF blend works for the southern
stream portion of the upper trough over the West. The 12Z CMC is
less slow with movement of this trough compared to the 00Z run,
but is still slow enough to warrant its dismissal. Progression of
this feature in the 12Z ECMWF/GFS is very similar and is
considered the basis for comparison. The 12Z NAM is a bit slower
than the ECMWF/GFS consensus, but much closer than the 12Z CMC. A
blend of the reasonably similar 12Z GFS/ECMWF/NAM is suggested.


...Northern stream portion of the trough in the West, kicking east
into the Great Lakes Tuesday and Wednesday...

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non CMC blend
Confidence: Average

Only minor placement and strength differences exist with a weak
surface low near the Great Lakes Tuesday. Aloft, the 00Z CMC 
remains slightly slower than the remaining deterministic guidance.
Better trough progression agreement is seen in the 12Z NAM/GFS and
12Z UKMET through 36 hours as well as the 12Z ECMWF.


...Slow moving closed low setting up in the western Atlantic,
south-southeast of Nova Scotia today into Tuesday...
...Accelerated development of a surface low in the vicinity of
Bermuda...
...Associated strong surface high settling into New England...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 12Z GFS/NAM/UKMET/ECMWF
Confidence: Average

The Atlantic low pressure system and northeast CONUS surface ridge
are handled quite similarly through 36 hours in all but the 00Z
CMC. Differences are minor until Wednesday morning at which point
some latitude and strength differences develop with the closed
low.


...Shortwave digging into the Northern Rockies Tuesday and the
northern Great Plains Wednesday...
...Surface low developing over Alberta and Saskatchewan Tuesday
with trailing cold front reaching the north-central U.S. Tuesday
Night and Great Lakes Thursday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General 12Z Model Blend
Confidence: Average

Decent agreement among 12Z guidance on the upper trough moving
into the northern Rockies Tuesday and the surface low tracking
just north of the US/Canada border Tuesday night through
Wednesday. The 12Z GFS is slightly more progressive aloft, but is
right in line with consensus with the surface low and 850mb temps.
A general model blend should suffice.


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

Jackson