Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1151 AM 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 Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall synopsis... An active pattern over Southeast and Pacific Northwest through Saturday. ...Primary Mid-level trough over the Four Corners, crossing south Texas Thursday and the Southeast Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 29/00Z ECMWF/UKMET and 29/12Z GFS Confidence: Average This leading shortwave trough off a ridge over the interior Pacific Northwest swings across northern Mexico tonight and Thursday before 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 2QPF along the western/central Gulf Coast compared to the 00Z ECMWF/UKMET. The 12Z NAM continues to diverge from consensus Thursday night with the interaction of the primary and secondary shortwave troughs over the southern Plains and the 00Z CMC is still slower than the consensus with the trough crossing south Texas, so neither solution is preferred. ...Southern part of secondary Mid-level trough digging down the Rockies from Canada to Mexico tonight through Thursday night... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 29/00Z ECENS/ECMWF/UKMET and some 29/12Z GFS Confidence: Average The southern end of this shortwave trough crossing the interior Pacific Northwest Ridge is in better agreement so far today. The 00Z ECMWF is now farther west than the 12Z GFS and 00Z 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 which is similar to the 00Z CMC solution of much less forcing into Mexico. ...Northern portion secondary Mid-level trough crossing the central Plains Thursday night/Friday and pushing off the Southeast coast Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 29/00Z ECENS/ECMWF/UKMET and some 29/12Z GFS 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. Earlier notes about the 12Z NAM and CMC hold that they are much 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. ...Longwave trough approaching the west coast of Canada Friday night/Saturday and downstream atmospheric river into the Pacific Northwest late Thursday into Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 29/00Z ECENS/ECMWF/UKMET blend Confidence: Average The passage of a shortwave and accompanying cold front into British Columbia Thursday will initially bring zonal flow into western Canada that amplifies as ridging increases ahead of an upstream shortwave Friday. Ensemble means and the remaining deterministic consensus suggest that the 29/12Z GFS and 29/00Z CMC remain too quick with the shortwave...so a blend of the 29/00Z ECENS/ECMWF/UKMET 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