Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 157 AM EST Fri Feb 07 2020 Valid Feb 07/0000 UTC thru Feb 10/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Latest Model Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Phasing troughs over the Mid-Atlantic/Northeast on Friday... ...Powerful surface low center advancing through the Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models reflect northern stream energy currently over portions of the upper Great Lakes and Midwest that will dig southeast and phase on Friday with the strong ejecting southern stream trough over the TN Valley and Gulf Coast states. The phasing of these systems will lead to a consolidated, but very powerful area of low pressure over the interior of the Mid-Atlantic and especially New England by late in the day. In fact, locally in a few spots across the Northeast, it is expected that there will be all-time low surface pressure records set for the month of February. This low center will then exit very quickly northeast through the Canadian maritimes Friday night and early Saturday. Model spread is very modest, so a general model blend will be preferred. ...Shortwave crossing the Plains and OH Valley by Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average Strong flow will continue to over-top a broad but dominant eastern Pacific/West Coast ridge axis through Friday which will allow subtle shortwave energy cresting the ridge to dive southeast across the central/northern Plains by Friday evening and then across the OH Valley on Saturday. A weak area of surface low pressure and a front will be associated with this energy. The 00Z NAM is a tad slower and occasionally a little deeper than the global models as the energy traverses the Midwest. The 00Z UKMET has trended in line with the remaining global model suite. So, will prefer a non-NAM blend with this system at this point. ...Deep trough/cyclone crossing the Pacific Northwest Saturday... ...Digging energy over the Great Basin/Southwest by Sunday... ...Downstream troughing over the northern Plains by Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS/ECMWF Confidence: Slightly above average A strong closed low will advance through the Aleutian islands and AK peninsula by early Friday, with strong shortwave energy then digging quickly southeast toward British Columbia and then across the Pacific Northwest Friday night through early Saturday. By Sunday, a portion of this initial surge of energy will quickly eject downstream across the northern Rockies and over the northern Plains. Meanwhile, a split in the upper flow will allow for a substantial amount of energy to then dig southward over the Great Basin and into the Southwest around the eastern side of a strong deep layer ridge developing offshore the West Coast this weekend. The 00Z UKMET has trended notably slower compared to its previous run and is in better agreement with the multi-model consensus as this energy arrives across the Pacific Northwest, and also to a large extent with the split flow evolution thereafter as energy breaks away and drops into the Southwest. By later Sunday, the UKMET is still perhaps a little too fast in swinging the energy down across southern California, but the trend appears favorable. Meanwhile, the northern stream energy breaking away and crossing the Plains and Upper Midwest through Sunday will be accompanied by a wave of low pressure and a new frontal zone. The 00Z NAM gradually becomes a little slower than the global models at the surface, and at least aloft may be a tad too deep. The 00Z UKMET for its part is now in line with the remaining model guidance. Overall, the 00Z GFS and 00Z ECMWF have the best model clustering and ensemble support, so a blend of these solutions will be preferred with the energy as it arrives across the Northwest, and then also with the split flow evolution thereafter. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison