Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 103 AM EDT Thu Jul 09 2020 Valid Jul 09/0000 UTC thru Jul 12/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z NAM/GFS Evaluation with Preliminary Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Closed low moving east across south-central Canada through Friday... ...Associated cold front crossing the northern Plains Wednesday/Thursday and the Great Lakes Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z ECMWF/ECMWF mean Confidence: Average South of a mid-level closed low tracking across southern Canada, a shortwave trough will organize and move east across the Mississippi River through Friday morning. Differences with the evolution of this feature impact placement of a related cold front at the surface. The 12Z CMC is the most aggressive and slowest with the mid-level shortwave while the 00Z GFS appears to be the fastest. The 00Z NAM is also a bit slow while the 12Z UKMET is less defined by the end of the week. Mesoscale convective details make for differences with respect to synoptic evolution in each model which is typical this time of year and keeping confidence average at best. ...Low pressure moving northeast along Eastern Seaboard into this weekend... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z ECMWF/12Z CMC blend Confidence: Average The 00Z NAM and 00Z GFS are quicker to bring a surface low northward along the East Coast through the end of the week. The 00Z GFS is the fastest to move the low northward and deviates from the relatively good run to run consistency seen in the past 4 cycles of the ECMWF/GEFS/CMC ensemble scatter low plots. The somewhat slower 12Z ECMWF/CMC are a better match to the ensemble clustering over the next 36-60 hours while the 12Z UKMET becomes slower than most guidance. While the models are well initialized with the current surface feature at 00Z, with mid-level ridging to the north of the advancing low, there is some question with how quickly the low will advance. There are also uncertainties with the upstream (OH Valley) trough evolution and subsequent influences on the mid-upper level flow which keeps confidence in the preference only near average. ...Trough moving into the Pacific Northwest Thursday night, over-topping the ridge into the Upper Midwest by Sat and diving into the OH Valley by Sunday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average The models show similarly with this system. ...Larger scale trof dropping into Pacific NW Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average Minor timing differences exist with the 00Z NAM and GEFS mean slightly slower to advance the trough axis eastward into the Pacific Northwest while the 12Z UKMET/CMC are faster. However, these differences in timing are small enough that a middle ground or general model blend appears reasonable across this area of the country. 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 with the 21Z issuance: www.weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination. pdf Otto