Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 316 AM EDT Fri Jun 19 2020 Valid Jun 19/0000 UTC thru Jun 22/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 07Z update: No significant changes noted with the rest of the 00Z guidance and no model blend preference changes needed as well. Eastern U.S. closed low and coastal front ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend day 1; less GFS blend for day 2/3 Confidence: Slightly above average An upper level low will remain spread out over the central Appalachians, Mid-Atlantic, and Northeast through this weekend before gradually lifting northeast off the east coast. Synoptically, the latest guidance shows above average agreement and consistency from run to run. The main differences lie on day 3 where the 00Z NAM shows a much slower exit of the coast compared to the GFS (which is a bit faster than the consensus) while the ECMWF lies in between. At the surface, some models hint at a low developing off the NC coast in the day 2/3 period, though the GFS lacks this feature in its deterministic run and many of the 18Z GEFS members do not show a feature as well. Meanwhile, the ECMWF and to some degree the NAM/UKMET/CMC, offer a stronger low with many more ECENS members developing it after 60 hours. From a sensible weather impact, only the UKMET brings much higher QPF to eastern NC with the other models well offshore. So, a general model blend is preferred for day 1 but then less weight is preferred toward the GFS for day 2/3. Closed low developing over northern high plains and parade of shortwaves across central Plains ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-GFS blend Confidence: Average A large upper low over Saskatchewan and Manitoba that will develop through this weekend is well agreed upon by the latest model guidance. However, individual shortwaves that will parade the southern periphery across the central Plains. The first shortwave comes through late Friday night into Saturday, where the GFS has been consistently a bit too deep/strong over Kansas/Missouri and then continues to be more amplified as it lifts into the Upper Mississippi Valley. As such, its low track is to the west of the model consensus,a bit slower, and stronger. For D3, another shortwave comes out into the central Plains and here there are more timing and strength issues. For now, the preference remains to exclude the GFS at this time and lean toward a ECMWF/UKMET/CMC blend. Troughs approaching the Pacific Northwest through Sunday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average Multiple shortwaves rotating through the broad Gulf of Alaska gyre will funnel an active weather pattern across the region through the weekend. The first shortwave reaches th B.C. coast late Friday night. Aside from a slightly fast GFS solution starting late in the day 1 period and continuing through day 3, the models are in average to above average agreement such that a general model blend is sufficient. Taylor Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml