Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 129 PM EST Tue Jan 07 2020 Valid Jan 07/1200 UTC thru Jan 11/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Surface low impacting the Mid-Atlantic/Northeast Today... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average 1830Z update: No significant changes noted with the rest of the 12Z guidance and will still lean on a general model blend preference. A compact, progressive shortwave trough currently advancing toward the Mid-Atlantic will move offshore later tonight. A weak area of low pressure currently analyzed over western NC is well agreed upon by the latest guidance. The low track clusters are tightly packed and any differences lie in the mesoscale, boundary layer and a general model blend is preferred. ...Northern stream trough crossing the Northeast by Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average 1830Z update: No significant changes noted with the rest of the 12Z guidance and will still lean on a general model blend preference. The models advance a northern stream upper trough and attendant cold front across the Great Lakes today, and then through the Northeast on Wednesday. Very good model agreement continues to be seen in the early 12Z guidance and older 00Z such that a general model blend remains the preference. ...Parade of shortwaves crossing the Pacific Northwest... ...Energy advancing east across the Plains/Midwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM, non-CMC blend Confidence: Average 1830Z update: The NAM remains on the slower end of the model spread and the GFS now is clearly on the faster side of the solutions with the rest of the 12Z guidance now available with the shortwave trough entering the Pacific NW and CA coast Thursday. As this wave quickly dives toward the Southwest US the differences seem to resolve themselves with just some typical timing biases. With the second system moving into the region late Friday into the weekend, overall model guidance is fairly good for Day 3, with the UKMET surface low track a bit behind the rest of the guidance. A series of shortwaves and impulses are forecast to impact the Pacific Northwest over the next 3 days as generally a trough west, ridge east pattern remains in place. The CMC is the initial outlier with its slower timing as well further south. The 12Z GFS is usable, though at 500 mb, its shortwave a bit more amplified than what the NAM or other guidance shows. The 12Z GFS is also faster than a lot of guidance and is way ahead of its ensemble mean. So while the preference is for a ECMWF/UKMET/GFS blend, higher weight is given toward the ECMWF/UKMET at this time. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor