Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1203 AM EST Sun Jan 05 2020 Valid Jan 05/0000 UTC thru Jan 08/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Shortwave trough/low impacting the Pacific Northwest... ...Energy ejecting out across the Plains/Midwest thru Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend Confidence: Above average The models are in good agreement with the shortwave tracking toward the Great Lakes region by Sunday night, and clipping the Northeast on Monday. The 12Z UKMET becomes a bit slower and deeper than the remaining suite of guidance as it edges toward northern New England by Monday. Will suggest a non-UKMET blend at this point. ...Split-flow trough near the Pacific Northwest by Sun... ...Energy reaching the Great Lakes/Northeast Tues/Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/12Z ECMWF/12Z ECENS/18Z GEFS blend Confidence: Average The models are in good agreement with the mid-level trough axis reaching the Pacific Northwest on Sunday. This energy will rapidly advance downstream with a weak low center clipping the northern Plains and reaching the Great Lakes by Tuesday. There will be some gradually amplification of the system as it crosses the Great Lakes and more so as it approaches the Northeast. The 12Z UKMET/CMC solutions appear a bit too slow in time with the system. The UKMET is also perhaps a little farther north with its upper trough/surface low evolution. As the system approaches the Northeast by Wednesday, the 00Z NAM becomes a bit of a deeper outlier, with the 12Z CMC also on the deep side of the guidance. The 00Z GFS and 12Z ECMWF are closest to the model consensus and have reasonably good agreement from the latest GEFS/ECENS means, and so a blend of these solutions will be preferred. ...Southern stream trough/low near the TN Valley by Tues... ...Surface low impacting the Mid-Atlantic/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM/GFS and 12Z ECMWF Confidence: Average The models take a shortwave trough in the southern stream and advance it across the lower MS and TN Valleys through Monday and Tuesday along with a wave of low pressure. This system will then cross the Mid-Atlantic by late Tuesday and deepen offshore southern New England by early Wednesday. The 12Z CMC is a deeper and slower outlier with this system, and gradually the 12Z UKMET appears too progressive. The better model clustering and ensemble agreement resides with the 00Z NAM/GFS and 12Z ECMWF, so a blend of these solutions will be preferred. ...Shortwave/fronts approaching the Pacific Northwest Mon... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM/GFS and 12Z ECMWF Confidence: Average Yet another in a series of shortwave troughs will arrive across the Pacific Northwest late Monday into Tuesday. Initially a warm front will cross the region ahead of this energy, and the guidance handles that relatively well, but the 12Z CMC is a tad slower than the model consensus with this feature. Then as the main shortwave and associated cold front arrives on Tuesday, the models are in good agreement with exception to the 12Z UKMET which is a tad out of phase with the other guidance. Will prefer a blend of the 00Z NAM/GFS and 12Z ECMWF for now which collectively show good clustering. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison