Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1152 AM EST Fri Jan 17 2020 Valid Jan 17/1200 UTC thru Jan 21/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Progressive central to eastern U.S. storm system... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS and 00Z ECMWF Confidence: Slightly above average A progressive upper trough crossing the Intermountain West along with a lead mid-level trough/closed low feature over the central Plains will generally consolidate later today and tonight over the Upper Midwest with a deepening area of surface low pressure. By Saturday, the guidance agrees in depicting a deep closed low crossing the Great Lakes that then opens up into a broad trough across the Northeast before exiting through southeast Canada by Sunday. The 12Z NAM and 00Z UKMET are a tad north of the multi-model suite of guidance with the low center as it crosses the Great Lakes, and the UKMET is more distinct northerly outlier relative to the track across the Northeast. The 12Z NAM and 00Z CMC both gradually end up a tad more progressive than the model consensus as the system crosses and exits the Northeast. Overall, the 12Z GFS and 00Z ECMWF both have good agreement with their mass fields and more closely represent the model consensus, and given good ensemble support, a blend of the GFS and ECMWF will be preferred. ...Amplifying shortwave crossing the Midwest Sunday/Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Slightly above average A progressive, but vigorous, northern stream shortwave will dig southeast from Canada and cross the Upper Midwest Sunday night before then swinging down through the OH/TN Valleys on Monday. The 12Z NAM ultimately ends up a tad slow with this system, but generally the model differences with this feature are minimal otherwise. A non-NAM blend will be preferred for the mass fields of this system. ...Shortwave/front clipping the Pacific Northwest by Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The guidance supports a progressive Pacific shortwave trough clipping the Pacific Northwest by early Monday. The 00Z CMC/UKMET are a tad deeper with the system compared to the 12Z NAM/GFS and 00Z ECMWF and suggest a somewhat better defined low center lifting near the northern end of Vancouver Island as a trailing cold front clips the coastal ranges of western WA. Will prefer a general model blend to resolve the model spread at this point, as there is at least some modest ensemble support for the CMC/UKMET solutions. ...Southern stream shortwave crossing California by Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z NAM/GFS and 00Z ECMWF Confidence: Average Southern stream shortwave energy will be crossing especially central/southern areas of California on Monday ahead of a deep upper trough/closed low farther offshore of the West Coast. The 00Z UKMET appears to be a bit too slow with this system, with the 00Z CMC probably too progressive. The model consensus is generally better represented by a blend of the 12Z NAM/GFS and 00Z ECMWF, and has good ensemble support, so a blend of these solutions will be preferred. ...Deep upper trough offshore the West Coast on Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z NAM/GFS and 00Z UKMET Confidence: Below average The guidance depicts a progressive and deep upper trough/closed low offshore the West Coast by Monday. The timing details of the system are generally well agreed upon, but the 12Z NAM/GFS and 00Z UKMET all take the closed low a tad south of the 00Z CMC and especially the 00Z ECMWF. The ensembles means are split as well, with the GEFS mean supporting the southerly camp, and the ECENS mean in favor of the ECMWF albeit perhaps a tad slower. The farther north ECMWF/ECENS mean consensus appears to be related to somewhat stronger energy these solutions have over the Gulf of AK. The preference for now will be toward the more southerly consensus, but with limited confidence. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison