Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1144 PM EST Sun Dec 09 2018 Valid Dec 10/0000 UTC thru Dec 13/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...North, Great Lakes and Northeast Tues/Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average 19z update: The 12z CMC trended a bit slower at least initially through the Great Lakes and matches the ECMWF, though does accelerate through New England like the 12z GFS by Wed. The UKMET shifted a bit deeper to match the ECMWF, and given the slight timing difference seen in New England with the GFS and CMC, will support a slight adjustment to support a 12z ECMWF/NAM/UKMET blend at slightly above average confidence. Along the southwest periphery of the larger scale global trough in northeast Canada, a shortwave trough will swing through the Great Lakes region into the Northeast US Tuesday into Wednesday. Overall, the ECMWF continues to be on the stronger side of the guidance envelope as it digs over the northern Great Lakes. But overall, a general consensus of the available guidance should suffice for this area of the CONUS during the Tuesday-Wednesday time frame. ...Pair of troughs through the West shifting into the Plains by late Tues/Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non-GFS, non-CMC blend Confidence: Below average A couple of shortwave troughs pushing onshore in the Pacific Northwest during the forecast period will cross through the Rockies into the central/northern Plains by Tuesday into Wednesday. Forecast confidence remains below to slightly below average with respect to the large scale synoptic pattern. For the first shortwave, most of the guidance does agree that it will take on a negative tilt by Wednesday as it moves into the Upper Midwest, lower Great Lakes region. The ECMWF is considerably further south with its axis, more so over Missouri compared to the rest of the guidance which agrees more on a Illinois/Iowa placement. By Thursday, some of the guidance (GFS) wants to lift it into the Great Lakes while some others (NAM/UKMET/CMC) push it further east into OH/PA. Finally, the ECMWF weakens the feature somewhat, opens it up as it lifts into WV. Behind it, an elongated secondary trough axis is forecast to spill out into the Plains region. The GFS is too deep with the southern feature, digging it well into Texas while the NAM/ECMWF/UKMET are more open and further to the north. The CMC seems to be an outlier, closing off the low further west into New Mexico. Beyond the current forecast period, there are considerable differences on how this feature will evolve as it moves east toward the Southeast US and Mid-Atlantic. See the PMDEPD for the medium-range uncertainty on this feature. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor