Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1243 PM EDT Thu Jul 18 2019

Valid Jul 18/1200 UTC thru Jul 22/0000 UTC

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

12Z Model Evaluation Including Preference and Forecast Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend 00Z ECMWF/UKMET and 06Z GEFS (Northwest and
Northern Plains)
            General model blend (rest of the CONUS)
Confidence: Average (Northwest and Northern Plains)
            Above average (rest of the CONUS)


The focus for the short term forecast period across the CONUS is
largely on the Northwest US and northern Plains where most of the
synoptic forcing and storm tracks will reside. The southern US
will be dominated by a building ridge and increasing heights as a
summer time heat wave locks in through the weekend.

Quasi-zonal flow across the northern tier of the US initially will
gradually transition to a more amplified pattern by Day 3. A
closed low over Vancouver Island will become positively titled and
sheared out through Day 2 with impulses of energy ejecting out
into the central northern Plains. Timing differences are noted
between the latest deterministic guidance, with the CMC/ECMWF
being a bit flatter/more progressive compared to the more
amplified NAM/GFS. The NAM/GFS are perhaps too strong with the
ridging building in its wake across the Northwest US and up the
Canadian Rockies and will favor a solution more like the ECMWF at
this time. By the end of the forecast period, more troughing is
expected to develop over the Great Lakes. This will push a cold
front through the Great Lakes, Northeast and Mid-Atlantic,
shunting the oppressive heat southward.

At the surface, a couple waves of low pressure will move through
the central Plains and Great Lakes early in the forecast period
where there's reasonable model agreement and minimal spread.
Eventually as the troughing takes hold over the east, Canadian
high pressure builds in the wake of the frontal passage.

For this cycle, the model blend preference was for a general model
blend outside of the northwest US and northern Plains. There, a
blend of the 00Z ECMWF/UKMET and 06Z GEFS was preferred, with more
emphasis/weight on the ECMWF.


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

Taylor