Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 226 PM EST Wed Jan 29 2020 Valid Jan 29/1200 UTC thru Feb 02/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall synopsis... An active pattern over Southeast and Pacific Northwest through Saturday. ...Primary Mid-level trough over the Four Corners now, crossing south Texas Thursday and the Southeast Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 29/12Z ECMWF/UKMET with some GFS/CMC Confidence: Average This leading shortwave trough off a ridge over the interior Pacific Northwest swings across northern Mexico tonight and Thursday then south Texas Thursday night. A secondary trough digs in behind Thursday night, weakening the mid-level energy as it crosses the Southeast Friday. The 12Z GFS remains farther north with Day 2 QPF along the western/central Gulf Coast compared to the 12Z ECMWF/UKMET which both trended south a bit. The 12Z NAM continues to diverge from consensus Thursday night with the interaction of the primary and secondary shortwave troughs over the southern Plains, so it is not preferred. The 12Z CMC has sped up a bit and is now reasonable enough to be included in the blend. ...Southern part of secondary Mid-level trough digging down the Rockies from Canada to Mexico tonight through Thursday night... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 29/12Z ECMWF/UKMET with some 12Z GFS/CMC Confidence: Average The southern end of this shortwave trough crossing the interior Pacific Northwest Ridge is in decent agreement among the 12Z suite. The 12Z ECMWF shifted east and is much more inline with the 12Z GFS/UKMET which favor the immediate lee side of the Rockies through Thursday night. This southern end feature then splits off into Mexico Friday with a trough over southern Texas. The 12Z NAM favors a northern stream low over the central/southern Plains and is an outlier. The 12Z CMC is more like consensus with the track and can be included now. ...Northern portion secondary Mid-level trough crossing the central Plains Thursday night/Friday and pushing off the Southeast coast Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 29/12Z ECMWF/UKMET with some 12Z GFS/CMC Confidence: Below Average Complex interaction of the northern stream portion of a secondary shortwave crossing the interior Pac NW ridge that breaks off late Thursday over the northern Plains and interacts with a trough over the Great Lakes Friday into Saturday. However, there is decent agreement that the resulting trough pushes off the southeast coast and stays offshore as it lifts north Saturday night/Sunday. The 12Z NAM is farther south than the preferred consensus of the EC/GFS/UKMET. There is still decent run-to-run variability of this feature and how the parts interact and the thermal differences so this remains a wait and see for a solid solution to be borne out. The 12Z CMC is more in line with consensus, so a solution may be coming together. One note about the 12Z ECMWF is it maintains a flatter trough over Florida which produces heavier Day 3 precip than consensus which limits is usage over that region. ...Longwave trough approaching the west coast of Canada Friday night/Saturday and downstream atmospheric river into the Pacific Northwest late Thursday into Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 29/12Z ECMWF/UKMET and 00Z ECENS blend with some 29/12Z NAM Confidence: Average The passage of a shortwave and accompanying cold front into British Columbia Thursday will bring initially zonal flow into western Canada that amplifies as ridging increases ahead of an upstream shortwave Friday. Ensemble means and the remaining deterministic consensus continue to indicate that the 29/12Z GFS/CMC are too far north... so a blend of the 29/00Z ECENS and 29/12Z ECMWF/UKMET/NAM remains is relative agreement for the trough position and the downstream atmospheric river moving into the Pacific Northwest. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Jackson