Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1245 AM EDT Mon Jun 25 2018 Valid Jun 25/0000 UTC thru Jun 28/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z model evaluation...including preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Closed low/trough crossing the Plains/Midwest Monday/Tuesday... ...Surface low crossing the Midwest/Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM and 00Z GFS Confidence: Average The guidance has reasonably good agreement with the details of the upper low and associated trough crossing the Plains and Midwest over the next couple of days. However, at the surface on Monday, the 12Z CMC tends to be a little north of the model consensus with the 12Z UKMET being a little farther south regarding the low pressure wave. By Tuesday, the guidance comes into better agreement on the track of surface low pressure, but as the low lifts across Ontario, the 12Z UKMET and 12Z ECMWF both edge a bit stronger than the 00Z NAM and 00Z GFS. The latest GEFS mean and ECENS mean are more supportive of the NCEP camp, so a NAM/GFS blend will be preferred. ...Upper level trough affecting the Northeast by Monday... ...Surface low tracking near Nova Scotia by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non_UKMET blend Confidence: Above average An upper trough will amplify across the Northeast by Monday and then evolve into a closed low near Nova Scotia through Tuesday. The 12Z UKMET edges a bit stronger and a little slower than the remaining models by Monday night as surface low pressure crosses southeast of Nova Scotia and then begins to pull away to the south of Newfoundland. Will prefer a non-UKMET blend. ...Upper trough crossing the Northwest Monday/Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 60 hours 18Z GEFS mean/12Z ECENS mean blend...after 60 hours Confidence: Average An upper trough will cross the Northwest on Monday and Tuesday in association with an upper low that moves across western Canada. The guidance overall is in good agreement with their mass fields, with only very modest timing/depth differences through Tuesday. On Wednesday, the bulk of the energy will focus over south-central Canada where there is some spread with how the energy elongates. The 00Z NAM, 12Z CMC and 12Z ECMWF suggest a more defined closed low feature, versus the 00Z GFS and 12Z UKMET which are much more elongated/flatter with the energy. Will prefer a general model blend through 60 hours, followed by a blend of the latest GEFS mean and ECENS mean thereafter which offer a nice compromise solution. ...Next upper trough arriving across the West by Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models begin to amplify an upper trough into the West by early Thursday. There is good mass field agreement with this system, so a general model blend will be preferred. ...Possible coastal cyclogenesis near the Southeast U.S. coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM and 12Z ECENS mean Confidence: Slightly below average There remains a signal in the model guidance for a wave of low pressure to develop along a stalled front near southeast NC by Wednesday morning. The energy for this is related to the MCV that is currently moving through the lower OH Valley and is expected to cross the southern Mid-Atlantic region over the next couple of days. The 12Z ECMWF and to an extent the 12Z CMC are the strongest solutions. The 00Z NAM and especially the 00Z GFS and 12Z UKMET are much flatter with any development. The 12Z ECENS mean though does reflect a signal for a low, but just not to the extent of the operational ECMWF. The latest GEFS mean supports the flatter consensus. Will lean toward the idea of there being at least a weak wave near southeast NC early Wednesday, and this would be close to a blend of the NAM and ECENS mean. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison