Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 225 AM EDT Mon May 11 2020 Valid May 11/0000 UTC thru May 14/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Surface low moving from Great Lakes to New England through Tuesday... ...Energy amplifying from the OH Valley to the Northeast Monday and Tuesday... ...Shortwave moving across the Great Lakes and Northeast Tuesday and Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average Large cyclonic flow will persist over the Great Lakes and eastern US through early this week with large height anomalies centered over the Hudson Bay region. A pair of compact shortwaves will work through base of the large scale closed low, the first of which moves from the Great Lakes today into the Northeast on Monday. A deepening surface low will track from near the Lower Lakes to the Gulf of Maine. The low track and depth is well agreed upon by the latest guidance through early Tuesday as the system tracks northeast from the Gulf of Maine into the Canadian Maritimes. In comparison to their 12Z runs, both the NAM and GFS are slower with the track of the low as it moves through the Gulf of Maine - putting them in better agreement with the ECMWF and EC Ensemble Mean. A secondary, compact shortwave is then forecast to wrap behind the initial system over the northern/interior New England states Tuesday/Tuesday night. Here, model agreement is relatively stable. The UKMET, which had been a relatively outlier with a slower solution across the New England, has trended toward the overall consensus. ...Shortwave energy crossing the Southwest on Sunday... ...Energy shearing across the southern Plains by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average A subtle shortwave will move through portions of the Desert Southwest today before crossing into the southern Plains and lower Mississippi Valley early next week. In the large scale sense, there are very little differences seen in the latest model guidance and a general model blend should more than suffice for mass field purposes. As the system ejects into the Plains, there are some magnitude differences in QPF but these should be resolved on a smaller scale than the synoptic pattern. ...Upper trough/closed low lifting along the Northwest Coast Monday-Wednesday... ...Upper low closing off over western Canada on Tuesday before moving east through the Canadian Prairie Wednesday-Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 12.12Z; non-NAM/UKMET thereafter Confidence: Average A longwave trough and closed low approaches the Pacific Northwest early in the week. As the system approaches the coast, it will slow/stall thanks to persistent ridging inland. The closed low will then wobble/meander through the end of the period. Pieces of energy will separate and move inland, interacting with another piece of shortwave energy/closed low over the southern Canadian Rockies. Into early Wednesday, a general model blend should be sufficient as there is little spread seen in the latest guidance. Beyond that time frame, the NAM/UKMET become relative outliers - indicating greater interaction between the Pacific and Canadian systems on Wednesday, with the Canadian low then slower to move east of the southern Canadian Rockies into the Canadian Prairie and northern Great Plains Wednesday night/Thursday morning. With the GEFS and EC Ensemble means favoring the favoring the faster camp, will recommend leaning away from the NAM and UKMET. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Pereira/Taylor