Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 250 PM EST Thu Jan 09 2020 Valid Jan 09/1200 UTC thru Jan 13/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Shortwave entering OR/CA tonight, amplifying across the Four Corners/High Plains Fri and through MS Valley into Great Lakes late Sat into Sun... ...Deepening surface low over the Lower MS Valley Fri/Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/ECMWF blend Confidence: Above average 19Z update: No significant updates noted with the rest of the 12Z guidance. The CMC remains a slow outlier while some components of the UKMET appear usable. The GFS/ECMWF compromise appear to be a good approach with the relatively good agreement in the mass fields through 3 days. Digging shortwave trough over southern California and the southwest U.S. will eject out into the southern/south-central Plains by this weekend, taking on a negative tilt over the Lower to Mid-MS River Valley. Aloft, there are still some differences noted where the 00Z CMC is slower than the rest of the deterministic guidance and the available ensemble means. The UKMET is in line with the GFS/ECMWF as far as timing initially but then tracks faster and further east by Day 3 as the system lifts into the Great Lakes. Overall, the GFS/ECMWF have been the most consistent over the last several model cycles and appear to be locking in on similar solutions. At the surface, there remains some latitudinal differences in the low track but a consensus approach leans toward a GFS/ECMWF blend while the UKMET/CMC offer the most different solutions. Though overall the differences in QPF appear fairly minimal and more on the mesoscale level. The overall differences are very small but with overall good agreement and within tightening ensemble suite, will support a 12Z GFS, 00Z ECMWF blend at slightly above average confidence, but still increasing. ...Next upper trough over the Northwest by Sat shearing into longer wave trof over Intermountain West Sun... ...Phasing/sharpening third shortwave along BC coast into Pac NW late Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 11.00Z; then non-NAM blend Confidence: Above average 19Z update: Typical biases remain in place across the Northwest (GFS fast; ECMWF slow) though the 12Z CMC did trend faster and now is closer to the ECMWF timing with the first system Friday/Friday night. The NAM still appears to be an outlier enough to not include beyond 11.00Z, so no real change to the model blend preference. Longwave troughing will generally be locked in place across the western/interior west through the forecast period as a series of systems work through the Pacific Northwest. Upper level energy bottled up across interior Canada slowly remains in place through the period, while a couple stronger, compact shortwaves move into the Pacific Northwest. The first, arriving late Friday into Saturday is now well represented and agreed upon by the latest model guidance where a general model blend can be applied (through 48 hours 11.00Z). Beyond that period, the NAM is too fast with the next shortwave and low pressure moving onshore and should be discarded beyond 60 hours. The GFS/ECMWF are in fairly good agreement though the GFS is a tad faster than the ECMWF. The CMC is on the slower side of the model spread, but could probably be incorporated as well. So outside of the very fast NAM for Day 2/3, the rest of the available models appear usable in the forecast period. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor