Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 244 PM EDT Sat May 11 2019 Valid May 11/1200 UTC thru May 15/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Final Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ An amplified upper level pattern will remain over the lower 48 through Tuesday with northern stream troughing approaching the West Coast for Monday, with downstream ridging over the western half of the nation and troughing over the eastern half of the nation. In addition, a southern stream closed low, currently offshore of the northern Baja Peninsula, will track into Texas for Monday night. There are three main systems to speak of which will have the greatest impacts on the lower 48 through Tuesday evening. ...Closed low moving through the Ohio Valley... ...Surface low development off of the East Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z NAM/UKMET/CMC blend Confidence: Slightly above average ...19Z update... Slight adjustments were made with the 12Z ECMWF/CMC toward the previous preference. Differences are not as large now with a slightly weaker trend in the 12Z ECMWF, but prefer to keep out its stronger solution at this time. ...previous discussion follows... An initial sfc-850 mb low will track through the upper Ohio Valley, with the 00Z ECMWF noted as a stronger outlier. While the ECMWF has been consistent with this feature, it has little support outside of its ensembles. The 00Z ECMWF position appears reasonable however. The 12Z GFS is slightly weaker than the consensus, so overall, a 12Z NAM/UKMET blend should reduce the strength of the 00Z ECMWF while increasing the 12Z GFS strength to a favorable compromise. ...Closed low approaching West Texas on Monday, weakening to an open wave by Tuesday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average ...19Z update... The preference was changed to a general model blend given the 12Z guidance is in fairly good agreement now with mass fields, however convective precipitation details are not so good. Please reference the WPC QPFERD for further details on this system and QPF preferences. ...previous discussion follows... Overall, model agreement with this feature is good except for the 00Z CMC which is a bit weaker with the mid-level low by Monday evening. Differences develop due to convective handling in the models, but for the purposes of this discussion focusing on mass fields, a 00Z ECMWF/12Z GFS blend matches well with the latest ensemble means. ...Upper trough/cold front approaching the Pacific Northwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average ...19Z update... Small changes in timing continue with the 12Z ECMWF/CMC, adjusting timing slightly faster. A general model blend still looks appropriate across the Pacific Northwest with this system. ...previous discussion follows... There are mainly timing differences with this system, the 12Z GFS/UKMET are faster while the 12Z NAM/00Z ECMWF/00Z CMC are a bit slower. The 12Z UKMET differs perhaps the most with the 500 mb pattern nearing the Pacific Northwest, but impacts to the coast do not appear that significant with a general model blend resulting in a solution close to the ensemble means which edge slightly to the slower side of the latest deterministic spread. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Otto