Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 408 AM EST Thu Nov 21 2019 Valid Nov 21/0000 UTC thru Nov 24/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Closed low crossing the Four Corners into the Plains Friday/Saturday... ...Potential northern stream shortwave crossing the north-central U.S. Friday night... ...Surface low moving from the lower Mississippi Valley into the central Appalachians Friday night into Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z ECMWF, 00Z UKMET, 18Z GEFS mean Confidence: Slightly below average 09Z Update: No significant changes with the latest model guidance. The 00Z GFS continues to be a bit of an outlier, so the preference will remain a ECMWF/UKMET/GEFS mean blend. ---previous discussion--- Anomalous closed upper level low over the southwest U.S. is expected to move into the southern/central Plains over the next 48 hours and eventually phase with northern stream energy to deepen troughing over the eastern 2/3 of the CONUS into this weekend. Model guidance has come into slightly better agreement through 48 hours with the large scale synoptic pattern, but confidence decreases and model spread increases for Day 3. The 00Z GFS has trended a bit slower with the closed upper level, and allows it to phase more with the northern stream energy by Saturday. This allows the parent/initial surface low to be pulled further northwest across the Ohio Valley compared to the rest of the guidance, which seems to favor a bit less phasing and therefore a faster solution. Looking at the ensemble guidance, there is better agreement between the ECENS and GEFS means, and the 18Z GEFS does favor a bit faster solution. For this reason, the favored blend will incorporate the 12Z ECMWF, 12Z UKMET, and the 18Z GEFS mean for now. ...Remainder of the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend (except non-GFS blend Pac NW) Confidence: Average There is relatively good agreement with the synoptic setup and evolution with the shortwave trough and associated low pressure moving across the Midwest and Northeast U.S. during the first couple days of the forecast period. While there are some subtle timing differences noted with the shortwave, those differences do not seem to be impacting much at the surface and sensible weather. As such, a general model blend is preferred. For the shortwave trough moving across the Pacific Northwest Friday, the GFS is much faster than the rest of the guidance and should be discarded across that region. Otherwise, the rest of the guidance is sufficient at this time. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor