Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 236 AM EDT Tue Jun 30 2020 Valid Jun 30/0000 UTC thru Jul 03/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Closed low anchored over New England ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The latest model guidance maintains the upper low over the interior of New England going through early Thursday. Thereafter, the energy is forecast to shift off the east-southeast and offshore of the East Coast. The 00Z CMC trended toward the faster model consensus late in the period as the energy advances offshore, and thus the guidance is now in very good agreement. A general model blend will now be preferred. Deep upper trough/closed low across the Intermountain West ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z UKMET/ECMWF/GEFS and 12Z ECENS mean Confidence: Average The strong upper-level low over the Intermountain West will lift northeast over the northern Rockies through Tuesday before merging with another shortwave trough and associated close low approaching southwest Canada. The consolidation of this energy will result in a large closed low over the Pacific Northwest to northern Rockies going through Wednesday. By Thursday, yet another compact shortwave and associated closed low will drop south down the coast of British Columbia and into the Pacific Northwest which will help to drive the larger closed low up into southwest Canada. The model consensus at this point is best approximated by the 00Z UKMET and 00Z ECMWF, with reasonably good support from the 00Z GEFS mean and yesterday's 12Z ECENS mean. The 00Z CMC did trend generally toward this consensus with some modest timing differences noted with the lifting of the closed low northward into southwest Canada. The 00Z NAM for its part is also modestly deeper than the model consensus with the broader large scale closed low evolution. The preference will be a blend of the UKMET/ECMWF solutions and the latest GEFS mean and ECENS mean. MCV/Weak mid-level low over northern MN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The MCV and associated weak mid-level closed low over northern MN this evening will lift north through western Ontario over the next 24 hours. Model spread is minimal with this evolution and so a general model blend will again be preferred with this feature. MCV crossing the middle and upper MS Valley Tuesday/Wednesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS/CMC/UKMET Confidence: Below average A convectively enhanced MCV is forecast to track through the middle and upper MS Valley region going through Wednesday. The 00Z GFS, 00Z CMC and 00Z UKMET all take energy farther north through the upper Midwest by late Wednesday, with the 00Z ECMWF slower and farther south over eastern IA as the energy dampens out. The 00Z NAM though stalls the energy out over western IL on Tuesday and then drops the energy southeastward through the Mid-South by Thursday. With limited confidence, the preference will be toward a blend of the more progressive and northerly tracking solutions which still has a fair degree of ensemble support. Mid-level closed low over the Gulf Coast by Friday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average A mid-level trough and developing closed low is expected to form over the Gulf Coast states by Friday as weak shortwave energy drops down through the Mid-South. The 00Z NAM is a bit stronger than the global models as it takes the aforementioned MCV over western IL down to the southeast which results in a more amplified trough over the Gulf Coast region. A non-NAM blend will be preferred for the time being since the global models are generally well clustered. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison