Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1211 PM EST Sat Jan 25 2020 Valid Jan 25/1200 UTC thru Jan 29/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep closed low moving across the Northeast through Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Very good agreement persists in the evolution of a strong closed low currently across the Ohio Valley lifting northeast slowly through the weekend. The main core of this feature has good model consensus that it will drift through New England by Sunday and then over Atlantic Canada on Monday. The guidance at least through Monday is agreeable such that a general model blend can be preferred. ...Shortwave crossing the northern Plains through Sunday... ...Energy then digging through the Midwest/OH Valley on Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average A shortwave currently over the northern High Plains will dive southeast across the Midwest and be racing across the OH Valley by late Monday. It will then reach the Mid-Atlantic coast Monday night. The 12Z NAM is a stronger outlier with this system, and so a non-NAM blend will be preferred. ...Shortwave crossing the Great Lakes late Monday... ...Dropping down across the OH Valley on Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS/00Z CMC/00Z UKMET Confidence: Average In the wake of the shortwave on Monday, a new northern stream shortwave will drop southeast and cross the OH Valley on Tuesday. The 12Z NAM tends to be a bit strong with this system, but the 00Z ECMWF appears to be too weak. Better model clustering resides with the 12Z GFS/00Z CMC and 00Z UKMET, so a blend of these solutions will be preferred. ...Split flow trough crossing the West coast on Sunday... ...Energy ejecting through the Southwest and Plains by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z NAM/GFS and 00Z ECMWF blend...northern stream Non-CMC blend...southern stream Confidence: Slightly above average The models all take a progressive split flow trough across the West Coast on Sunday, with a southern stream portion of the energy then dropping down across the Southwest and amplifying into a closed low as it approaches the southern High Plains by early Tuesday. Meanwhile, the northern stream component of the trough will be over the northern High Plains. The 00Z CMC is an outlier with both northern and southern stream components as it is likely too strong/slow and too far north with the southern stream energy, and too slow with the energy in the northern stream. The 00Z UKMET also appears to be too slow/deep with its handling of the northern stream energy. A non-CMC blend will be preferred with the southern stream evolution, and a NAM/GFS/ECMWF blend with the northern stream evolution. ...Progressive upper trough over the Pacific Northwest Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z NAM and 00Z UKMET/ECMWF Confidence: Average Yet another in a series of Pacific shortwave troughs will arrive on Tuesday across the Pacific Northwest. The 12Z GFS and 00Z CMC are deeper outliers with this system, although there is some support for a relatively deeper solution from the GEFS ensemble suite. The 12Z NAM and 00Z UKMET/ECMWF solutions are all weaker and have better support from the CMCE/ECENS suites. So, will prefer the relatively weaker consensus. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison