Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 138 AM EST Mon Jan 06 2020 Valid Jan 06/0000 UTC thru Jan 09/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Shortwave trough crossing the Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in good agreement with the shortwave advancing through the Northeast through Monday and Tuesday, and thus a general model blend will be preferred. ...Energy reaching the Great Lakes/Northeast Tues/Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models advance the progressive shortwave trough over the Pacific Northwest rapidly downstream over the next 24 to 36 hours with a weak low center clipping the northern Plains and reaching the Great Lakes by Tuesday. There will be some gradual amplification of the system as it crosses the Great Lakes and more so as it approaches the Northeast by Wednesday. The latest guidance is now in sufficiently good agreement with timing and depth that a general model blend can be preferred. ...Southern stream trough/low near the TN Valley by Tues... ...Surface low impacting the Mid-Atlantic/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z ARW/ARW2/GEMregional blend...through 48 hrs Non-GFS blend...after 48 hrs Confidence: Slightly above 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 gradually deepening wave of low pressure. This system will cross the Mid-Atlantic by late Tuesday and deepen further offshore southern New England by early Wednesday. The guidance overall has trended a tad stronger with this system, and have come into better timing/depth agreement with the 00Z cycle. One notable exception is the 00Z GFS which is generally a progressive and deeper outlier after 24 hours. The 00Z ARW/ARW2/GEM regional solutions of the hires suite tend to favor the non-GFS consensus at least through 48 hours. The 00Z NMMB however appears to be a tad too suppressed with its low track. So, a blend of the 00Z ARW/ARW2/GEM regional solutions will be preferred through 48 hours, with a non-GFS blend after the 48 hour time frame. A non-GFS blend may also be used in conjunction with the aforementioned hires model suite for the early part of the period. ...Shortwave/fronts approaching the Pacific Northwest Mon... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Slightly above average Yet another in a series of shortwave troughs and associated fronts will arrive across the Pacific Northwest late Monday into Tuesday. By Wednesday, this system will be traversing the Intermountain West and there will be lee-side cyclogenesis east of the Rockies and over the High Plains. The 00Z NAM is just a tad slower than the model consensus as the system advances inland and traverses the West. A non-NAM blend will be preferred given good agreement seen out of the global models. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison