Prognostic Meteorological Discussion
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FXUS10 KWNH 231657

Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1156 AM EST Fri Feb 23 2018

Valid Feb 23/1200 UTC thru Feb 27/0000 UTC

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

12Z model evaluation...with latest model preferences and confidence

...Surface wave crossing the Great Lakes/northern New England...
Preference: General model blend
Confidence: Above average

The models are in good agreement with the ejecting the surface
wave currently crossing the Great Lakes region that will clip
portions of northern New England tonight. A general model
orientation of the surface front across the South this period, and
also with the details of the surface wave lifting up across upper
Mississippi Valley and Great Lakes. A general model blend will be

...Strong shortwave over the Four Corners region today...
...Cyclogenesis over the Plains and lifting to the Midwest...
Preference: Blend of the 12Z GFS, 00Z UKMET and 00Z ECMWF
Confidence: Slight above average

The models take a strong shortwave trough digging down across the
Four Corners region today and eject it out across the Plains on
Saturday where well-defined cyclogenesis will occur. An upper
trough will then lift northeast across the upper Midwest by
Saturday night and take on a negative tilt which will help to
deepen surface low pressure as it lifts across the upper Great
Lakes region by early Sunday. The 12Z NAM ends up again stronger
aloft with its energy traversing the upper Midwest and places its
surface low northwest of the model consensus as it nears the upper
Midwest and upper Great Lakes. The 00Z CMC also is a bit deeper
aloft like the NAM. However, the 12Z GFS, 00Z UKMET and 00Z ECMWF
are not as strong with the height falls, but nevertheless show an
energetic and negatively tilting upper trough with a rather strong
surface low. The GFS, UKMET and ECMWF show good model clustering
and ensemble support, and so a blend of these solutions will be

...Shortwave arriving over the Pacific Northwest on Saturday...
...Crossing the Four Corners/High Plains on Sunday...
...Ejecting east across the Mississippi/Ohio Valleys on Monday...
Preference: Blend of the 12Z GFS and 00Z ECMWF
Confidence: Average

The next in a series of shortwaves to drop southeast down across
western North America and into the Pacific Northwest will arrive
on Saturday and then rapidly drop down into the Four Corners
region on Sunday before rapidly ejecting east toward the mid
Mississippi Valley and Ohio Valley on Monday. The models are in
good agreement with their mass field details of this system until
Sunday when the 00Z UKMET begins to lag the model consensus, and
the 12Z GFS begins to outrun it just slightly. The 00Z CMC and 00Z
ECMWF tend to favor the slower UKMET, with the 12Z NAM close to
the GFS. The 06Z GEFS mean is close to the operational GFS, with
the 00Z ECENS mean close to the operational ECMWF. The UKMET is
slower than any of the model ensemble means though and will be
discounted by Sunday and Monday. Accounting for the slower and
faster camps, the preference will be to compromise by favoring a
GFS and ECMWF blend.

...Shortwave arriving over the Pacific Northwest on Sunday...
...Larger scale trough evolution over the West by Monday...
Preference: Blend of the 12Z GFS and 12Z ECMWF
Confidence: Average

The guidance brings another shortwave into the Pacific Northwest
on Sunday along with a progressive cold front. The guidance is in
good agreement with the arrival of the shortwave energy and the
evolution of the height falls digging down across California and
the Great Basin on Monday which will lead to a larger scale trough
evolution aiming for the Southwest. Given the good larger scale
agreement among the guidance with this energy at this point, a
general model blend will be preferred.

Model trends at
500 mb forecasts at

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