Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1236 PM EDT Tue Jun 16 2020
Valid Jun 16/1200 UTC thru Jun 20/0000 UTC
...See NOUS42 KWNO (ADMSDM) for the status of the upper air
ingest...
12Z Model Evaluation Including Initial Preferences and Forecast
Confidence
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Southeast U.S. closed low and coastal front
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Preference: General model blend
Confidence: High
The cut-off upper low that is currently parked over South Carolina
is expected to remain nearly stationary through Wednesday evening
before gradually lifting north and eventually becoming absorbed by
the westerlies by the weekend. This is supporting a surface low
near eastern North Carolina that is fueling convection and heavy
rain for portions of the Southeast and Mid-Atlantic region. The
models are indicating very good synoptic scale agreement on the
progress of the upper level system. At the surface, the 12Z NAM
is slightly weaker with the low, but still within the realm of
possibilities. Therefore, a general model blend with high
confidence can be recommended.
Closed low moving into the Northwest Tuesday into the Northern
High Plains by Thursday
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Preference: General model blend through 00Z Friday, then 12Z
NAM/00Z UKMET/00Z ECMWF blend
Confidence: Moderate
The upper level low over Washington and Oregon Tuesday morning is
forecast to cross the northern Rockies and become absorbed by a
second evolving upper low over south-central Canada by Thursday.
This will sustain an occluded surface low and a slow moving cold
front across the Dakotas through the middle of the week. The two
main differences noted in the guidance is a stronger system with
the 12Z GFS across Saskatchewan and Manitoba, and the CMC becomes
displaced to the south by 00Z Friday, and therefore its surface
low is farther south near the U.S./Canadian border compared to the
other guidance. Therefore a blend of the 12Z NAM/00Z ECMWF/UKMET
should suffice as a starting point in the forecast process.
Hamrick
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml