Prognostic Meteorological Discussion
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000
FXUS10 KWNH 041849
PMDHMD

Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
248 PM EDT Sat Apr 04 2020

Valid Apr 04/1200 UTC thru Apr 08/0000 UTC

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

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

...Overall Pattern Across the CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
 Exception: Less GFS blend after 07.00Z for western U.S.
Confidence: Slightly above average

19Z update: With the rest of the 12Z guidance now available, there
is not a large or significant difference with the system over the
western U.S. to deviate from the previous blend preference. The
GFS remains an eastern/faster solution where less of it should be
used for day 3. Otherwise, a general model blend should suffice.

---previous discussion---
Shortwave energy moving through the northern Rockies will lift
into southern Canada over the next 12-24 hours and with the large
closed low dropping down the western U.S. coast, quasi-zonal flow
is forecast to set up across the central/eastern U.S. through the
next 3 days. A couple features of interest for the CONUS include
the aforementioned western U.S. closed low. Through 07.00Z, the
most recent model guidance shows favorable agreement as the low
drops south off the California coast. After 07.00Z, some timing
issues remain where the 12Z GFS remains a faster solution and is
also centered further east, closer to the coast. The 12Z run did
shift more favorably to the rest of the guidance such that more of
its QPF (and mass fields) could be used in a blend (compared to
its earlier runs which were considerably further inland and an
outlier). Another feature is a northern stream shortwave that
moves from British Columbia through the northern Rockies Monday
into Tuesday. Despite some marginal timing issues (UKMET a bit
fast, GFS/NAM slow), a general model blend should suffice for this
area. Elsewhere across the CONUS, model differences are not
significant enough to stray from a general model blend

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

Taylor


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