Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1145 PM EST Fri Mar 08 2019 Valid Mar 09/0000 UTC thru Mar 12/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z NAM/GFS Evaluation Including Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Positively tilted shortwave trough moving east into Manitoba and Ontario this weekend... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z CMC blend Confidence: Slightly above average The 12Z CMC stands out from the remaining guidance with a stronger and somewhat slower trough axis moving through Manitoba on Sunday. The CMC has been trending toward the consensus but it doesn't appear to be there just yet. Will favor a non 12Z CMC blend for this system. ...Surface low tracking across the Upper Midwest/Great Lakes through Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z CMC blend Confidence: Slightly above average Fairly good agreement in the deterministic and ensemble guidance with this system, but the 12Z CMC is displaced west of the consensus with its 500 mb low by Sunday morning over the Great lakes region. This affects the 850-700 mb low placement in the 12Z CMC through Sunday/Sunday night with a westward deviation from the remaining consensus. A non 12Z CMC blend shows good agreement and is recommended here. ...Closed low over Washington this morning, interacting with the next Pacific trough/surface low nearing California later today, developing into a large closed low over or just offshore of California Monday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z CMC blend Confidence: Slightly above average The ECMWF ensemble mean has shown excellent continuity with the timing of the eventual large closed low forecast to develop near the California coast through Sunday night. Meanwhile, the past 4 12/00Z cycles of the GEFS has trended slower to match the ECMWF members. Only the 12Z CMC and a couple of ECMWF ensemble members remain fast through Tuesday morning. Decent agreement is in place with a non-12Z CMC blend. ...Progressive upper trough approaching the Pacific Northwest Tuesday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM, 00Z GFS, 12Z ECMWF blend Confidence: Average Model agreement is not as good with this system compared with the ones above. The ensemble means differ on the timing of the next shortwave trough to affect the Pacific Northwest Monday night into Tuesday. The 12Z ECMWF mean is faster than the 12/18Z GEFS with the 21Z SREF slowest. The latest deterministic guidance is within the relatively tight packing of ensemble members through 12Z/12 except for the faster 12Z CMC. A blend on the non 12Z CMC models is recommended. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto