Prognostic Meteorological Discussion
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FXUS10 KWNH 240635

Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
235 AM EDT Sat Mar 24 2018

Valid Mar 24/0000 UTC thru Mar 27/1200 UTC

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

00Z model evaluation...including final preferences

...Deep trough/closed low offshore the Northwest early this
morning, opening up into a pair of shortwaves moving into the
Intermountain West this weekend...
...Shortwave currently near the Aleutians digging down the West
Coast Sunday and leading to trough amplification and renewed
Plains lee cyclogenesis by Monday...
Preference: 00Z ECMWF/00Z UKMET blend
Confidence: Average

The differences out West are minor until Monday morning when
energy diving down the western U.S. coastline results in a large
southern stream trough/closed low forecast to anchor over the Four
Corners region early in the week. The GEFS and GFS has been
trending faster with the leading edge of the southern stream
trough, but the 00Z GFS did back off a little ending 12Z/27. The
00Z NAM is faster as well with a weak surface low moving across
the central Plains on Monday compared to the remaining available
guidance. The amplified nature of the upper pattern over the
eastern Pacific into the western U.S. supports an evolution near
the consistent ECMWF mean...which lies nearest to the 00Z ECMWF,
00Z CMC and 00Z UKMET. The 00Z CMC, however, is slightly slower
with the initial surface low moving through the central Plains
Monday night. Prefer to stay toward the consistent ECMWF mean.

...Shortwave traversing the Midwest this morning and becoming
sheared out as it pushes through the Ohio Valley and Carolinas...
...Accompanying surface low cross the the middle Mississippi
valley today, weakening into the southern Appalachians Sunday
morning in favor of a surface low developing offshore of the
Preference: non 00Z NAM blend
Confidence: Slightly above average

The 00Z NAM remains slightly north of the deterministic/ensemble
consensus concerning a surface low moving through the TN valley.
The difference is small, but the ensemble scatter low plots
continue to support a non 00Z NAM/21Z SREF consensus with the 21Z
SREF north like the 00Z NAM.

Concerning the secondary surface low, the models have come into
better agreement until the surface low moves well offshore into
the Atlantic.

No significant differences were noted with the 00Z ECMWF/UKMET/CMC
compared to their previous 12Z cycles.

...Arctic shortwave digging sharply south through Quebec on
Saturday with closed low developing off the Northeast by Sunday...
...Associated strong surface high settling into New England...
Preference: 00Z NAM/ECMWF/UKMET blend
Confidence: Average

Despite trending slightly slower, the 00Z GFS continues to take
the 500 mb low more quickly into the Atlantic compared to the
remaining consensus. Ensemble spaghetti plots continue to support
a slower solution. The 00Z CMC is also slower, but it is weaker
with the upper trough/closed low through 12Z/27 in the western
Atlantic. The 00Z NAM, 00Z ECMWF and 00Z UKMET are similar and
agree well with the ensemble guidance outside of the GEFS, which
matches the GFS. No significant differences were noted with the
00Z ECMWF/UKMET/CMC compared to their previous 12Z cycles.

Model trends at
500 mb forecasts at


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