Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1200 AM EST Thu Jan 30 2020 Valid Jan 30/0000 UTC thru Feb 02/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...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 29/12Z CMC and 30/00Z GFS Confidence: Average A leading shortwave trough off a ridge over the interior Pacific Northwest early this evening will swing across northern Mexico through Thursday then south Texas on Thursday night. A secondary trough digs in behind Thursday night, weakening the mid-level energy as it crosses the Southeast Friday. The 30/00Z NAM had decent run to run consistency, but that left the NAM on the slower side of the envelope of solutions. ...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 30/00Z NAM Confidence: Below Average Complex interaction of several streams lead to a below average confidence forecast from Thursday night through Saturday. One 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 latest runs show a split between the NCEP models and the non NCEP models with regards to the formation (or not) of a closed low that drops into the southeastern U.S. as shown by the NCEP camp or a broad, deep and fairly unified flow pattern by the non-NCEP. Initially, thought the 30/00Z GFS deepened the low too much and brought it well too far south by Saturday morning to be usable...but the 30/00Z NAM made a movement towards the GFS idea. For the moment, will give the nod to the 30/00Z NAM due to its somewhat weaker idea and less interaction with shortwave energy coming in from the Ohio/Tennessee Valley by Saturday afternoon. Overall, think that the NCEP guidance showing some southern stream mid level vort/low makes sense given the presence of a 120 to 140 kt upper level jet across the Gulf...but the using some combination of the 29/12Z ECMWF and the 30/00Z NAM could yield a reasonable compromise solution. ...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/ECENS blend with some 30/00Z NAM Confidence: Average The passage of a shortwave and accompanying cold front into British Columbia on Thursday will bring initially zonal flow into western Canada that amplifies as ridging increases ahead of an upstream shortwave Friday. Given reasonably good run-to-run consistency in the 30/00Z NCEP guidance, deterministic consensus and ensembles continue to favor a 29/12Z ECMWF/UKMET and 30/00Z NAM 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 Bann