Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1145 PM EST Sun Jan 05 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: Blend of the 00Z NAM/GFS and 12Z ECMWF Confidence: 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 gradually amplification of the system as it crosses the Great Lakes and more so as it approaches the Northeast by Wednesday. The 12Z UKMET is on the faster side of the guidance with the system as it arrives across the Great Lakes and Northeast. Conversely, the 12Z CMC is on the slow side of the guidance with this energy. A blend of the 00Z NAM/GFS and 12Z ECMWF will be preferred at this time with this system. ...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 00Z NAM/12Z UKMET/12Z ECMWF blend...after 48 hrs 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 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, but the 12Z CMC currently appears to be too far north with its low track. The 00Z GFS for its part is likely too progressive and especially as the system approaches and then moves away from southern New England. The better model clustering resides with the 00Z NAM/12Z UKMET and 12Z ECMWF. The 00Z ARW/ARW2/GEM regional solutions of the hires suite tend to favor this consensus as well 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 the 00Z NAM/12Z UKMET and 12Z ECMWF after the 48 hour time frame. The latter model camp may also be used in conjunction with the aforementioned hires suite for the early part of the period. ...Shortwave/fronts approaching the Pacific Northwest Mon... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS/12Z CMC and 12Z ECMWF 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. The 00Z NAM is just a tad slower than the model consensus, with the 12Z UKMET somewhat on the faster side of the model suite. As this energy advances into the Intermountain West, a notable broadening and deepening of the upper trough is expected. The NAM remains on the slower side of the guidance with the UKMET faster through the period. So at this point, a blend of the 00Z GFS/12Z CMC and 12Z ECMWF will 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