Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1225 PM EDT Thu Apr 09 2020 Valid Apr 09/1200 UTC thru Apr 13/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep cyclone impacting the Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-GFS blend Confidence: Above average An anomalously deep closed low crossing the Great Lakes will deepen and take on a negative tilt as it approaches the Northeast this afternoon/evening. Meanwhile, low pressure crossing the interior of NY state and New England will consolidate over coastal areas of Maine this evening and deepen into an intense low center. The 12Z GFS is overall a tad deeper than the 12Z NAM and the 00Z non-NCEP solutions. The GFS also tracks its surface low a tad farther inland over Maine versus the more concentrated low center evolution along the Maine coast that the remaining guidance favors. This results in the GFS having a somewhat stronger warm nose wrapping farther inland. The preference will be toward a non-GFS blend at this time. ...Slow-moving closed low across the Southwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-GFS blend Confidence: Slightly above average The models gradually eject the large, slow-moving cut-off southern stream low over southern California off to the east over the next couple of days. The energy is expected to open up into a progressive shortwave trough over the southern Plains by Saturday which will then lift northeast and go negative tilt over lower MS Valley and Mid-South by Sunday as it comes under the influence of stronger northern stream height falls dropping down over the Midwest. The 12Z GFS, just like its previous runs, continues to be the fastest solution as the energy ejects out across the South. With its faster height fall progression, the GFS is also faster with its surface frontal progression and wave activity, and actually ends up with a somewhat stronger surface low compared to the other models by Sunday. The 12Z NAM is generally in agreement with the 00Z non-NCEP models with a modestly slower timing and modestly weaker surface reflection. The latest ensembles means suggest a solution generally a little slower than the GFS for the time being, so the latest preference will be for a non-GFS blend with this energy. ...Upper level trough/cold front reaching the Northwest... ...Dropping through the northern Plains/Midwest on Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z CMC/UKMET and ECMWF Confidence: Average Shortwave energy along the southern coast of Alaska will progress eastward to the Yukon territory, and with the accelerating/exiting jet, the upstream ridge will break down and allow for greater propagation east and then southward across southwestern Canada. The height falls will overspread the lee of the Canadian Rockies and then the northern High Plains, and support a surface cold front dropping southeastward across the northern Plains and Midwest by Sunday. The 12Z NAM tends to be a little more aggressive with its height falls over the Midwest by Sunday, and the 12Z GFS may be a little too fast with its surface frontal progression, so the preference with this energy will be to generally minimize the NAM/GFS camps, and favor more weighting toward the 00Z non-NCEP solutions for now given better clustering/ensemble support. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison