Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1220 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: Non-UKMET 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. Toward the end of the period, the 00Z UKMET becomes a bit weaker and faster with the closed low evolution, and appears a tad more out of tolerance with the surface low reflection over southeast Canada. Therefore, a non-UKMET blend will be preferred. Troughs approaching British Columbia and Pacific Northwest ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-GFS blend 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 00Z non-NCEP models led by the UKMET are all a little faster than the 12Z NAM/GFS solutions with timing of the second shortwave trough. The GFS is also a tad deeper than the remaining guidance. For now, a non-GFS blend will be preferred given better ensemble support for the non-GFS model consensus. Mid-level energy lingering over the lower MS Valley/Texas ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS and 00Z ECMWF Confidence: 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 and 00Z CMC both appear to be a bit too strong with the mid-level energy. The better model clustering tends to be with the 12Z GFS and 00Z 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