Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1213 AM EDT Tue Jul 03 2018 Valid Jul 03/0000 UTC thru Jul 06/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z model evaluation including preferences and forecast confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Upper trough advancing into Quebec tonight with accompanying cold front into the Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show similar timing/shape and strength with this system. ...Westward moving upper circulation along the Gulf Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The small upper low translating across the Gulf states currently remains fairly well agreed upon in the mass fields. The 00z NAM is a bit stronger in the mid-levels further south by late Wed and is generally matched with the placement of the 00z GFS, however still tracks well in timing, longitudinally, with the remaining guidance/ensemble suite. Given the minor difference, a general model blend will suffice with increasing confidence given the overall shape/timing/strength. ...Upper low approaching the southeastern U.S. coast by mid-week... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-CMC blend Confidence: Slightly above average Goes-east WV shows well defined TUTT cell northeast of the Bahamas, and guidance has been fairly consistent in its shape and timing over the next day or so. However, as the wave reaches FL, the 12z CMC begins to lag and shift northeast of the main clustering...enough to suggest removing it from the blend. The 00z NAM is bit stronger and favors the mid-level trof to be centered a bit south and east, but not dramatically so, but perhaps would be best to weight a bit lower, given the stronger agreement and continuity with the overall trend. As such a non-CMC blend is supported at slightly above average confidence. ...Upper low/trough taking shape over Canadian Rockies/Pacific Northwest today...lifting across Northern Plains/S Canadian Prairies into Wed/Thurs...and eastern Canada Fri. Surface wave(s) along Northern Plains Wed/Thurs before frontal zone crosses Great Lakes Fri. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ Preference: 00z GFS and 12z ECMWF/UKMET blend Confidence: Average The 00z NAM has significantly changed from prior guidance in favoring a very strong SW portion of the trof crossing the Columbia River Valley which in turn closes off into a deep more concentric shortwave out of the Salmon River Ranges into W MT by Wed, when the continuity/trends have been to be more progressive in centering east of the Canadian Rockies...this leads it to be much to slow/strong by 00z Thurs. The 12z CMC is also a bit stronger but also too slow. Uncharacteristically, the 12z ECMWF is the fastest guidance member calling it into some question (or at least the other guidance), but is in line with the ECENS mean and prior runs. The 00z GFS continues to trend toward the ECMWF/UKMET and along with the GEFS mean can be incorporated in the blend to account for the modest to high spread in the guidance overall. As such a 00z GFS and 12z ECMWF/UKMET is supported even as the wave crosses Ontario/Quebec with the trailing front in the Great Lakes. Confidence is average in this blend. ...Shortwave nearing Canadian West Coast and becoming closed low off U.S. West Coast by late Wed to Fri... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The 00z NAM has shifted a bit further west and is now very close to the growing model consensus. Even though the evolution and translation back to the northeast is well into the future, guidance has been very consistent around the overall timing/shape near this general model blend clustering; enough to support above average confidence 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 Gallina