Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 154 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 exiting the Northwest... ...Energy ejecting east across the northern tier states... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average The models are in good agreement with the shortwave exiting the Northwest and crossing the northern Plains/Upper Midwest through Sunday. By Sunday night and Monday, this energy will cross the Great Lakes and New England. The global models are now in good agreement with this energy, but the 00Z NAM is seen as being a little stronger and somewhat out of tolerance with the global models as the system crosses the Great Lakes, southern Quebec and northern New England. A non-NAM blend will be preferred. ...Split-flow trough near the Pacific Northwest on Sun... ...Energy reaching the Great Lakes/Northeast Tues/Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS/UKMET/ECMWF 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 by Wednesday. The 00Z CMC gradually appears to be a tad too slow with this system, and the 00Z NAM is an outright deep outlier. The 00Z GFS/UKMET/ECMWF solutions are now well clustered and have good ensemble support 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 weak 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 00Z CMC has overall trended toward the multi-model consensus, but may be a tad too slow still, and especially as the system advances offshore the East Coast. The 00Z ECMWF for its part is reasonably close to the NAM/GFS camp, but in the last 12 hours (forecast hour 72 to 84) of the short range period, the ECMWF becomes the strongest solution with a deeper low/mid-level low track and more direct impact in across southeast New England. The trend of the ECMWF and even to a modest extent the 00Z UKMET are suggestive of there being more influence/interaction with the northern stream energy crossing the Great Lakes and interior of the Northeast in the Tuesday/Wednesday time frame. For now, the prior preference of blending the 00Z NAM/GFS and yesterday's 12Z ECMWF will be maintained. ...Shortwave/fronts approaching the Pacific Northwest Mon... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above 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, with the main trough crossing by late Tuesday. There is some modest timing spread, but overall the agreement appears good enough that a general model blend can 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