Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 129 PM EST Thu Feb 13 2020 Valid Feb 13/1200 UTC thru Feb 17/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with preferences & confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Overall Pattern Across the CONUS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Exception: 12z GFS/NAM/UKMET blend for late Sat/Sunday in Pacific NW Confidence: Above Average but slightly below average for exception 19z update for the Pacific Northwest day 3: The 12z Non-NCEP suite trended toward the GFS/NAM, though the ECMWF/CMC slowed, they are both much weaker and still appears to be out of tolerance relative to the initial preference to have included but have some increase in overall confidence. The UKMET slowed as well but also showed greater amplification, and while a tad slower than the initial preference, there better congruence for inclusion in the blend. So a GFS/NAM/UKMET blend is preferred but still at slightly below average confidence. ---Prior Discussion--- A very quiet large scale pattern across the CONUS is initially dominated by a large Arctic high pressure area across the Plains today that is pressing a lingering warm conveyor/frontal zone across the East Coast today into early tomorrow (Fri). Guidance as been quite agreeable with both the exiting system and the High as it dominates the eastern half of the CONUS through Sunday. The active area will be the Pacific northwest, where a few shortwaves will cross the area through the short-term forecast period. The first, currently impacting Vancouver Island will press through Washington into the northern Rockies through today and tomorrow. As it slides eastward, the main energy and QPF will remain along/just north of the US/Canadian boarder with some increase of Great Lakes QPF by Sunday. While there is some spread, a general model blend will suffice given the timing/shape is good across the CONUS. A weak shortwave will progress through BC into Saturday, continuing to direct moisture/onshore jet across the Pacific NW, affecting mainly orographic QPF, but general disturbed weather, with very little large scale model spread to get too picky about. ~~~ Pacific Northwest Day 3 ~~~ However, by late Saturday, the next more amplified shortwave will cross through the Southeast Gulf of AK, directing toward southern BC/WA, with sizable timing differences. Uncharacteristically, the ECMWF, CMC are slightly greater amplified with the leading edge of height-falls. The 12z NAM/GFS continue to favor slightly stronger (increasing diffluence) jet energy approaching the wave and amplifying it later on Sunday and closer to the coast compared to the ECMWF, which is already ashore. The UKMET typically a bell-weather on which direction to favor, is in between but has a very strong upper level/flat jet to not really side with either camp. The difference in the evolution/timing does not afford a general model blend/compromise in this scenario; and traditional known negative biases are also opposite (example: the NAM is too amplified on day 3, and it is generally weaker overall with this run). So there is very low confidence in this system's timing, but overall evolution, UL jet enhancement evolution and longer term trends suggest The GFS/NAM may have a slightly better handle on the situation, with the UKMET tipping slightly toward this camp over the faster ECMWF/CMC pair. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina