Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1206 PM EST Tue Jan 21 2020 Valid Jan 21/1200 UTC thru Jan 25/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with latest Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ ...Closed low off the Southeast Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: General model blend Confidence: Above average The upper low dropping across the Southeast will continue east-southeast and offshore tonight before crossing just north of the Bahamas on Wednesday. Relatively strong cyclogenesis will occur over the next 12 to 24 hours, with low pressure then pulling east and well away from the U.S. by later Wednesday and Thursday. The guidance comprised of the global model suite and shorter range hires models show relatively good agreement with the timing evolution of the low, with just some modest spread with the depth of surface low pressure. At this point, a general model blend will be preferred since no one solution at this point appears to be an outlier. ...Current upper low/trough crossing into the Pacific Northwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: General model blend Confidence: Above average The deep layer closed low just offshore the Pacific Northwest will weaken into a progressive trough as it crosses British Columbia through tonight, but is forecast to then reorganize and deepen over southern Alberta on Wednesday before dropping southeast across the northern High Plains. At least through Wednesday, the models are in good agreement with this system. ...Binary interaction of closed lows over the Plains on Thursday... ...Consolidated deep layer closed low over the OH Valley Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: 12Z GFS/00Z UKMET/00Z ECMWF blend...Thursday 00Z ECENS mean (or GFS/UKMET/ECMWF blend)...Friday Confidence: Below average Guidance continues to suggest binary interaction of closed lows across the Plains on Thursday, with one closed low dropping southeast across the northern Plains, and another developing farther south over the central Plains/lower MO Valley by late Thursday. At least through Thursday, the 12Z NAM appears to be a deep outlier with the collective mass field evolution, with the 00Z CMC too slow. By early Friday, the two closed low begin to consolidate and move through the OH Valley. The 12Z GFS and 12Z NAM are farther north with the merged system, with the NAM notably slower/deeper. Of the 00Z non-NCEP models, the UKMET is similarly as fast as the GFS, but is farther south. The CMC and ECMWF are also both farther south but slower. The latest GEFS mean favors the farther north/faster GFS, but the latest CMCE/ECENS clusters are a little slower yet a little north of the deterministic CMC/ECMWF. The model preference through Thursday will be for a blend of the GFS/UKMET and ECMWF, however, by Friday preference will be toward the 00Z ECENS mean which best approximates the model consensus, and acts a blend of the GFS/UKMET and ECMWF solutions with their latitudinal and timing spreads. Confidence in the details of the mass field evolution remains limited. ...Shortwave crossing the Pacific Northwest on Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: General model blend Confidence: Above average The models bring a progressive, low-amplitude shortwave in across the Pacific Northwest on Friday. The global models show decent agreement with the 12Z NAM a tad more out of tolerance. Will prefer a non-NAM blend at this point. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison