Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 251 PM EDT Mon Jun 22 2020 Valid Jun 22/1200 UTC thru Jun 26/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Closed low over Ontario/Quebec Shortwaves over the lower MS/OH Valleys ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The large closed upper level low over western Ontario will advance gradually east over the next couple of days into Quebec as a larger scale trough extending south from this crosses the Midwest, Great Lakes and OH Valley. Meanwhile, separate convective enhanced vorts/shortwaves will eject across the lower MS Valley and the OH Valley generally ahead of the larger scale height falls. Model mass field spread is largely minimal with these shortwaves as they lift northeast over the next 24 hours and begin to dampen out. Regarding the deeper layer trough and closed low, the models show relatively good agreement with some modest spatial and depth spread with the height falls and the surface low reflection. A general model blend will be preferred as a result at this point. Troughs approaching British Columbia and Pacific Northwest ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z NAM/CMC/UKMET Confidence: Average A pair of shortwave troughs will approach the Pacific Northwest over the next couple of days, the first impacting mainly British Columbia through tonight. A second, stronger shortwave trough digs across the Pacific Northwest mid-week and edges into the Intermountain Region by Thursday. Model spread is minimal with the first impulse. However, the 12Z ECMWF becomes a relatively weaker and more progressive outlier with the second shortwave trough. The 12Z GFS is also a tad deeper than the remaining guidance with the second impulse. The better model clustering and ensemble support resides with the 12Z NAM/UKMET/CMC guidance at this point and so a blend of these solutions will be preferred. Mid-level energy lingering over the lower MS Valley/Texas ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS/ECMWF Confidence: Slightly above average The models suggest some of the convectively driven shortwave energy lingering over the lower MS Valley over the next couple of days which will tend to separate out from the westerlies and may actually tend to retrograde westward. The 12Z NAM appears overall to be a bit too strong with the mid-level energy. The better model clustering tends to be with the 12Z GFS and 12Z ECMWF with this energy, and so a blend of these solutions will be preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison