Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 249 PM EDT Tue Jul 28 2020 Valid Jul 28/1200 UTC thru Aug 01/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation Including Preliminary Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-upper level troughing over the Great Lakes and Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average Only minor timing differences were noted with the mid-level closed low/trough that slowly moves east into the Northeastern U.S. over the enxt few days. Similarly with the related cold front at the surface, differences are relatively minor with the position with the deterministic and ensemble guidance showing reasonable agreement regarding this system. No significant adjustments were noted with the 12Z ECMWF/UKMET/CMC compared to their previous 00Z cycles. ...Mid-level energy over Great Basin... ...Energy advancing southeast across the Plains for Wednesday/Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z UKMET blend Confidence: Average A mid-level over western Wyoming today is expected to reach the Great Plains by Thursday morning, which when combined with smaller scale disturbances nearby results in a longwave trough over the central U.S. by the end of the week. Only the 12Z UKMET differed significantly from the remaining deterministic consensus and ensemble means, with the UKMET noted to be faster with the main mid-level shortwave reaching the Plains. The previous 00Z UKMET was stronger and slower aloft. Otherwise, ensemble spread is average for the center of the U.S. by Friday evening. While the 12Z UKMET is not an outlier, it falls within the minority of the available ensemble guidance. At the surface, a low along a slow moving frontal boundary will impact the central/southern Plains into the Mississippi Valley. Ensemble scatter low plots depict significant spread in latitude and longitude by 00Z/01 with even the stronger 12Z NAM within the clustering and not unreasonable. ...Upper low/trough approaching the Pacific Northwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average Similar to the mid-upper level trough impacting the Northeast, there is reasonably good agreement with the closed low advancing east toward the Pacific Northwest Thursday and Friday. There are some minor timing differences with the 12Z NAM slowest and 12Z UKMET fastest, but all of the deterministic models are close enough to support a general model blend for this system. Only minor timing differences were noted with the 12Z ECMWF/UKMET/CMC compared to their previous 00Z cycles. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml This product will terminate August 15, 2020: www.weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination. pdf Otto