Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 244 AM EDT Sun Apr 05 2020 Valid Apr 05/0000 UTC thru Apr 08/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Exception: Non-NAM from Northern High Plains to Great Lakes Mon-Wed Confidence: Slightly above average 19z update: The 00z UKMET was a tad faster and north relative to the closed low and its prior run but still well within an acceptable envelope, but also builds some confidence toward the faster NAM/GFS solution...still believe a general model blend will work for the closed low. The northern stream shortwave and associated surface low/frontal zone through the Ohio Valley/Great Lakes on Day 3, saw little sizable change with exception of the ECMWF trending even slightly faster. This reduces confidence in this solution as it may be too weak and fast. Still, so will reduce some of the ECMWF influence in a preferred blend here, but still a Non-NAM blend is best. ---Prior Discussion--- Expanding/deepening closed low along the West Coast dominates the large scale CONUS mass fields, with a strong/well defined subtropical jet streaming across Northern Old Mexico into/along the Gulf Coast states. A shear axis/pair of shortwaves are well north of the US/Canadian border at this point; though it will continue to extend eastward under the strong Arctic anticyclone, eventually the wave consolidates and clips northern New England Monday, broadening and maintaining NW flow influence through the remainder of the period. While the 12z CMC is initially slower it is not terribly so and the overall evolution through the Northeast can be supported by a general model blend. Back to the west, the closed low has also started to consolidate in model spread/evolution; and while there remains some internal shortwave/vorticity center differences, the evolution is only slightly different. The GFS had been much more phased to the northern stream, both making it generally weaker but also progressing it faster, but the 00z run has tempered this a bit. It remains a faster solution in the overall suite, but more in the realm of acceptable bias, especially combined with typical acceptable biases being slower in the ECMWF/CMC and too strong (tad fast) with the 00z NAM. As such a general model blend is supported but still a tad lower weight to the GFS. The sharp northern stream trof across BC/Alberta will be pressed eastward by the stronger upstream Pacific jet, with some small timing differences. Mainly the 00z NAM is a bit stronger and slower with its eastward progression and southeastward height-falls across the northern Plains. The resultant cold front/surface lows match initially but eventually track well south and slow in the surface low cluster suite to remove it from any preference at this time. The 00z GFS, as alluded to before, is more disconnected with the southern stream closed low and become more progressive like the ECMWF, even surpassing the 12z UKMET/CMC. Still, with the ECMWF being fastest, that is a uncharacteristic position within the suite, so will hedge a bit toward a non-NAM blend overall. So to encapsulate the CONUS preference, a general model blend is supported with the exception of the 00z NAM across the northern tier to the Great Lakes from Mon to Wed. with perhaps a tad less weighting to the GFS by the end of day 3 in S CA. Confidence is slightly above average in this blend for the mass fields; however, the QPF across the Mid-MS valley to Gulf Coast is not. The return moisture under influence of the height-falls/surface cyclone across the Plains into the MS Valley is not well agreed upon both in magnitude and timing, so convective activation is a bit less certain, and so below average with QPF placement. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina