Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 315 AM EDT Sun Jun 21 2020 Valid Jun 21/0000 UTC thru Jun 24/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Closed low over Manitoba/Ontario and associated parade of shortwaves across the Great Plains to Midwest ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend day 1/2; non-NAM blend day 3 Confidence: Slightly Below Average 07Z update: No significant changes noted with the rest of the 00Z guidance. Through the next 3 days, the large closed low currently over Manitoba will be the main weather feature over the CONUS. Several shortwave troughs are expected to round this low, interacting with existing fronts which will be the focus for convective complexes over much of the central US. The evolution of the large closed low as it wobbles toward the northern Great Lakes is well represented and agreed on with the latest model guidance. The exception is by day 3 there are some spatial differences, with the UKMET and NAM drifting further southeast while the GFS is centered back to the northwest. Surface low pressure will move from the central Plains toward the Great Lakes through early next week, with again some spatial spread seen in the latest guidance. The NAM is a slower solution, holding back the low to the south while the rest of the guidance is progressive, resulting in notable QPF differences. For this reason, a non-NAM blend is preferred for day 3 while a general model blend should suffice for large scale mass field purposes for day 1/2. Troughs approaching the Pacific Northwest Tuesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model Blend Confidence: Average A couple of shortwaves will move onshore the Pacific Northwest through Tuesday, rounding the base of a deep Gulf of Alaska low. Some timing and strength differences are seen in the latest deterministic guidance but the effect on sensible weather and QPF is minimal such that a general model blend should be sufficient. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor