Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1222 PM EDT Sun May 24 2020 Valid May 24/1200 UTC thru May 28/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation Including Initial Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Shortwave trough crossing the Great Lakes through Sunday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: High A rather compact mid to upper-level low center crossing the Midwest this evening will be advancing across the Great Lakes region on Sunday and weakening with time as it tracks over the top of a strengthening deep layer ridge over the Southeast U.S. On Monday, a weak remnant of this energy will cross through northern New England. The models are in good agreement with this system, and so a general model blend will be preferred. Synoptic scale trough over the West evolving into closed low over southern Plains ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z UKMET/ECMWF/EC mean blend Confidence: Average The latest guidance shows very good agreement in bringing a new large scale upper trough and associated closed low in across the Intermountain West through the weekend. By Monday, the models support this deep trough edging toward the Plains with one closed low center exiting the northern Rockies and crossing the northern High Plains. Meanwhile, a second closed low will be attempting to focus over the central Rockies, and by Tuesday the guidance is in reasonably good agreement on the idea of a new closed low becoming well-defined over the southern Plains. Leading up to this closed low evolution over the southern Plains, there will be a pair of shortwave troughs, one on Sunday and one on Monday, that will round the base of the larger scale trough and lift northeast across the southern Plains. The first shortwave is expected to evolve out of the MCS activity currently impacting areas south-central TX and the middle Rio Grande Valley. The second and more dominant shortwave is currently showing up very distinctly across the Southwest U.S. and northwest Mexico, and is moving steadily off to the east. This energy will lift northeast through Sunday night toward the lower MS Valley as the second upstream shortwave trough arrives and ultimately fosters the upper low development over the southern Plains by Tuesday. Mid-level trough and weak surface low impacting Florida early in the week ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z NAM/GFS/00Z ECMWF blend Confidence: Average An upper level ridge will be building across the Southeast and the East Coast through the beginning of the week. South of the upper ridge will be a low-mid level trough axis that will gradually lift northward to the eastern Gulf of Mexico, with a weak surface wave of low pressure likely developing along it by Monday. Although this does not appear particularly impressive in terms of mass fields, it will be significant for QPF purposes. Given that the 00Z UKMET is more suppressed with the 700 mb trough across Cuba and the Florida Straits, this keeps the heaviest rainfall farther south than the relatively well clustered NAM/GFS/ECMWF. The 00Z CMC also appears farther south with its QPF axis on Day 2 across South Florida. An initial blend consisting of the 12Z NAM/GFS/00Z ECMWF should work well and maintains good continuity with earlier preferences. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hamrick