Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 419 AM EST Fri Nov 22 2019 Valid Nov 22/0000 UTC thru Nov 25/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Weakening closed low crossing the Four Corners into the Plains Friday/Saturday, phasing with potent northern stream shortwave across Great Lakes Sat into Sun... ...Surface low moving from the lower Mississippi Valley into the central Appalachians Friday night into Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model Blend Confidence: Average 09Z update: No significant changes noted with the rest of the 00Z guidance now available. The general model blend preference still appears sufficient. ---previous discussion--- Closed low over the Southwest U.S. and Four Corners region will continue to make progress eastward over the next couple of days, ejecting out into the southern/central Plains Friday night into Saturday. This system is then forecast to phase with northern stream energy over the Great Lakes and lead to a fairly anomalous negative tilted trough over the Northeast U.S. by late in the weekend with a surface low deepening from the TN Valley toward the Mid-Atlantic. Model agreement has increased somewhat in the last cycle or two, especially with the mid/upper level pattern where for the most part, differences are minimal. At the surface however, there remains some spread with respect to the low track, where the majority of the GEFS members are south (southern Appalachians) while the ECENS members are to the north (OH Valley). As the low moves off the Mid-Atlantic coast, the spread lessens some and there is reasonable consensus. From a sensible weather perspective, QPF footprint is fairly similar across the mid-Atlantic and Northeast, with difference mainly being in magnitude. With this in mind, a general model blend would suffice for this time period. ...Embedded shortwaves within strong zonal northern Pacific Jet into the Northwest... ...Associated surface wave across the Northern Tier by 00z Mon... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non-CMC blend Confidence: Average Fairly active northern stream energy will bring a parade of shortwaves across the northern tier of the U.S. during the short term period while a large closed low drifts well offshore the southern California coast. The large scale synoptic setup and evolution is fairly represented by the various deterministic models through about 48 hours, but then the 12Z CMC seems to diverge from the consensus. It is much weaker with the energy coming into the Pac NW on Sunday and then is slower with the next feature coming in early next week. So both its temporal and magnitude differences suggest it as an outlier from this cycle. Otherwise, the relatively good consensus in mass fields and lighter QPF favors a general model blend (excluding the CMC). Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor