Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
233 AM EDT Wed Oct 30 2019

Valid Oct 30/0000 UTC thru Nov 02/1200 UTC

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

00Z Model Evaluation with Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Powerful closed low over the central Rockies Wed...
...Energy crossing the the Plains/Midwest/OH Valley Thurs...
...Cold front/surface wave impacting the eastern U.S...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM blend...weighted toward the 00Z GFS/ECMWF
Confidence: Slightly above average

Vigorous shortwave energy currently dropping down through the
Intermountain West will reach the central Rockies on Wednesday and
foster a very strong mid-level closed low which will cross the
central Plains and portions of the Midwest and OH Valley through
Thursday. As the energy crosses the OH Valley, it is expected to
become negatively tilted and is forecast to then rapidly lift
northeast across the lower Great Lakes and Northeast Thursday
night and Friday morning. Multiple waves of low pressure
developing along an attendant cold front will initially evolve
over portions of the TN/OH Valleys by late Wednesday, but these
lows will consolidate into one dominant wave of low pressure which
will deepen over the upper OH Valley on Thursday before lifting up
through the lower Great Lakes and Northeast. A strong cold front
trailing south from the surface low will cross the eastern U.S.
and reach the East Coast by later Thursday night.

The model guidance has finally come into better agreement with the
system, and in particular with the GFS siding with the more
consistent ECMWF with the 00Z cycle. The NAM from 48 hours onward
takes the closed low north of the global model consensus, and also
appears to be too deep as the energy crosses the Great Lakes and
adjacent areas of southeast Canada. The UKMET and CMC are
relatively close to the GFS/ECMWF camp with timing and depth now.
A non-NAM blend will be preferred with a weighting toward the
GFS/ECMWF camp.


...Next upper trough/front over the Plains/Midwest by Fri/Sat...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend...through 60 hours
            Non-NAM blend...after 60 hours
Confidence: Above average

Another strong shortwave trough and associated cold front will
quickly drop southeast across the Plains and Midwest Friday and
Saturday. Model spread is minimal among the global models, but the
NAM is seen as being a tad more out of tolerance toward the end of
the period as it becomes a little slower/deeper with the mid-level
trough over the upper Midwest, and is also a little farther south
with its surface low over the upper Great Lakes. A general model
blend should suffice through 60 hours, but a non-NAM blend will be
preferred thereafter.


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

Orrison