Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1210 AM EST Wed Jan 08 2020 Valid Jan 08/0000 UTC thru Jan 11/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Northern stream trough crossing the Northeast on Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models advance a northern stream upper trough and attendant cold front across the Northeast on Wednesday. Very good model agreement continues, and so a general model blend will again be preferred. ...Initial shortwave crossing the Pacific Northwest... ...Energy advancing east across the northern Plains/Midwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 36 hours Non-NAM blend...after 36 hours Confidence: Above average The models are in good agreement with the current shortwave that is moving across the Pacific Northwest. This energy rapidly ejects out across the Plains and Upper Midwest going through Thursday. The 00Z NAM though eventually appears to be a tad too far north with its downstream low track near the Upper Midwest, Upper Great Lakes and portions of Ontario. A general model blend will be preferred through about 36 hours, but thereafter, a non-NAM blend will be preferred. ...Shortwave amplifying across the Four Corners/High Plains... ...Deepening surface low over the Lower MS Valley Fri/Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z UKMET/CMC/ECMWF Confidence: Average A second shortwave trough crossing the Pacific Northwest early Thursday is expected to dive southeast and become detached from the westerlies as it crosses the Four Corners region. This energy then will amplify sharply out across the southern Plains on Friday, before then beginning to lift northeastward through the lower/mid MS Valley by Saturday. A very strong frontal zone will be setting up across this region for the weekend, and low pressure will be developing along it and riding northeastward. The 00Z NAM/GFS solutions are more progressive than the 12Z non-NCEP models as the energy ejects across the southern Plains and lower/mid MS Valley. The NAM also ends up being a bit stronger with its height falls compared to the global model suite. The latest GEFS and ECENS suites support a somewhat slower trough evolution like the collective non-NCEP camp, and as a result, the more progressive NAM/GFS solutions will, not be preferred at this time. Another consideration is the anomalously strong downstream ridge developing over the southwest Atlantic which should tend to foster at least a less progressive southern stream flow pattern. So, for now, a blend of the 12Z UKMET/CMC/ECMWF solutions will be preferred. ...Next upper trough over the Northwest by Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average Yet another shortwave trough will cross into the Northwest by Saturday. The 00Z NAM appears to be a tad too deep and slow with this system. The global models are rather well clustered though, and thus a non-NAM blend will be preferred with this system. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison