Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 159 PM EST Sun Jan 19 2020 Valid Jan 19/1200 UTC thru Jan 23/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with latest Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ ...Shortwave/front clipping the Pacific Northwest by Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: General model blend Confidence: Above average The guidance is generally in good agreement with the progressive, low-amplitude nature of this system brushing by the Pacific Northwest on Monday. Given the very modest model mass field spread, a general model blend will be preferred. ...Amplifying shortwave crossing the Midwest through Monday... ...Closed low evolution over the Southeast by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: Non-NAM blend Confidence: Above average A progressive, but vigorous, northern stream shortwave will dig southeast from Canada and cross the Upper Midwest tonight before then swinging down through the OH/TN Valleys on Monday. By Tuesday, the system will deepen into a closed low over the Southeast before going out to sea. Model spread with this has decreased compared to yesterday, but after seeing the latest 12Z cycle of guidance, the 12Z NAM has come in again as being a tad stronger than the global model consensus as the energy crosses the Southeast and then moves offshore. A non-NAM blend will be preferred now as a result. ...Southern stream shortwave crossing California by Monday... ...Energy crossing the Southwest/Plains Tuesday and Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: Non-GFS blend Confidence: Slightly above average Southern stream shortwave energy will be crossing southern areas of California on Monday ahead of a deep upper trough/closed low offshore of the Pacific Northwest. This energy will then eject quickly down across the Southwest on Tuesday and eject east across the Plains on Wednesday. The 12Z GFS has at least trended a tad deeper and slower with this system, and toward the already relatively deeper/slower 12Z NAM and non-NCEP suite of guidance. The 12Z ECMWF though came in slower compared to its previous run, and is now overall the slowest solution. The NAM by the end of the period may be just a tad too deep with its trough over the southern Plains, but it is definitely not outside the broader ensemble envelope, especially relative to the ECENS suite. On the flip side, the GFS overall may still be a tad too progressive at the end of the period, and there are concerns with its height falls evolution upstream over the Pacific Northwest and the northern High Plains. Despite the favorable GFS mass field trends across the southern tier, the preference will still be to limit the GFS incorporation into the model preference. So, based on these latest trends and clustering, a non-GFS blend will be preferred which will also help to resolve the relatively slow ECMWF. ...Upper trough/closed low over the Pacific Northwest by Tuesday... ...Energy ejecting out across the northern Plains Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: Blend of the 12Z NAM/CMC/ECMWF Confidence: Slightly above average A deep upper trough and associated closed low will arrive across the Pacific Northwest on Tuesday, with the energy then quickly advancing east across the northern Plains on Wednesday. The 12Z GFS is out of tolerance with the 12Z NAM, and the entire non-NCEP suite of guidance. It generally becomes a slower and relatively deeper outlier as it crosses Pacific Northwest, and down toward the High Plains. There is some modest support from the GEFS ensemble suite for the GFS, but the ECENS/CMCE camps are in favor of the non-NCEP consensus minus the UKMET. The UKMET trended more progressive and is likely a progressive outlier by the end of the period. Based on the latest trends/spread, a blend of the NAM, CMC and ECMWF will now be preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison