Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 248 PM EDT Tue Mar 27 2018 Valid Mar 27/1200 UTC thru Mar 31/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z model evaluation...including model preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Southern stream trough over the Four Corners advancing east... ...Surface low tracking from the lower Mississippi valley Thursday morning to the Northeast Friday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z UKMET, 12Z CMC and 12Z ECMWF Confidence: Slightly below average The models take the southern stream closed low over the Four Corners region and eject it east out across the southern Plains by Wednesday as a progressive trough axis. The system will then lift quickly northeast up across the Ohio Valley Thursday night and then across the Northeast on Friday around the east side of stronger northern stream height falls over the northern Plains and upper Mississippi Valley. There are still some notable timing differences seen in the guidance with the low evolution. The 12Z NAM is a progressive outlier with the system. Meanwhile, the 12Z GFS is slower but also a bit farther to the left with its low track compared to the model consensus. The biggest and presumably the most improved solution from the 12Z cycle is the ECMWF which trended notably slower and away from its faster 00Z solution. The latest ECMWF has good support from the CMC and UKMET as well with timing and intensity overall. This non-NCEP camp of guidance is all clustered a bit east of the GFS solution, and with the 12Z GEFS mean also a bit east of the deterministic GFS, a preference toward the non-NCEP model consensus will be preferred. Confidence does remain somewhat limited given the model spread overall and some of the run to run inconsistencies. ...Northern stream trough currently over the northern Plains... ...Lifting northeastward across eastern Canada by Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in good agreement with this system so a general model blend will be preferred. ...Shortwave digging across the northern Rockies today... ...Energy ejecting across the northern Plains Wednesday... ...Surface low crossing near the U.S./Canadian border... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in good agreement with this system so a general model blend will be preferred. ...Shortwave moving over the Northwest by Friday... ...Surface low dropping down across Montana... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS, 12Z GEFS mean and 00Z ECENS mean Confidence: Average The models bring a shortwave in across the Northwest by Friday and drop a surface low down across Montana. The 12Z UKMET is the slowest solution, with the 12Z NAM, 12Z GFS, 12Z CMC and 12Z ECMWF all faster. The ECMWF and especially the NAM are north of the model consensus with their low tracks though. Stronger ensemble support lies with the GFS as the GEFS mean and ECENS mean favor the GFS timing and latitudinal track of the wave. The latest CMC solution also favors the GFS in this regard. Will lean toward a blend of the GFS, GEFS mean and ECENS mean 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 Orrison