Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 205 PM EST Wed Jan 08 2020 Valid Jan 08/1200 UTC thru Jan 12/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Initial shortwave crossing the Pacific Northwest... ...Energy advancing east across the northern Plains/Midwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show similarly with this system with only minor differences remaining in the latest model guidance. No significant differences were noted with the 12Z ECMWF/UKMET/CMC compared to their previous 00Z cycles. ...Shortwave amplifying across the Four Corners/High Plains... ...Deepening surface low over the Lower MS Valley Fri/Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z NAM/12Z ECMWF/12Z UKMET Confidence: Average A shortwave trough is expected to cross the West Coast early Thursday morning and amplify across the Southwest through Thursday night. A northern stream component will track east through the north-central U.S. before lifting into Canada by Saturday afternoon. There is good agreement with the northern portion but timing differences show up with the southern, more powerful shortwave which should eject out into the Southern Plains Friday night. With a +1 to +2 standardized anomaly 500 mb ridge slowly spreading north from the Caribbean into the western Atlantic off of the East Coast through Saturday, the faster 12Z GFS seems to be a lower probability scenario. However, an upstream shortwave trough will act as a kicker, preventing too much in the way of a slow down across the Southern Plains. Currently, the only trend observed in the ensemble cycles is for more amplification versus a faster or slower trend. The ensemble distribution shows the 12Z GFS on the fast end with the 12Z CMC on the slow end of the latest guidance. The 00Z ECMWF mean is slightly ahead of the 00Z and 12Z ECMWF, so a blend between the 12Z ECMWF, 12Z UKMET and faster 12Z NAM is preferred at this time, attempting to represent a middle ground solution. A subtle slower trend in the 12Z ECMWF, faster trend in the 12Z UKMET and a more notable slower trend in the 12Z CMC was noted relative to their previous 00Z cycles. ...Next upper trough over the Northwest by Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The deterministic and ensemble guidance shows reasonable agreement with this system. Minor amplitude differences show up by Saturday with the 12Z ECMWF/UKMET trended slightly weaker out West compared to their previous 00Z cycles. Given differences are minor through the end of the short range (00Z/12), a general model blend will be preferred at this time. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto