Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 103 PM EDT Fri Aug 02 2019 Valid Aug 02/1200 UTC thru Aug 06/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation and Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Central/Southern Plains... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show mid-level shortwave energy dropping down across eastern KS tonight and early Saturday before then advancing south down across the southern Plains toward the Red River Valley of the South. The models have come into better agreement with their timing and strength, and so a general model blend will be favored with this energy. ...OH Valley/Mid-Atlantic/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above Average An upper trough will be swinging across the Northeast U.S. this weekend as a deepening closed low impacts portions of southeast Canada. Meanwhile, the guidance supports a shortwave impulse dropping southeast from the Great Lakes region and crossing the upper OH Valley and the Mid-Atlantic region going through Monday. The 12Z UKMET may be tad too weak with this shortwave, but the guidance is otherwise in good agreement with the timing and depth of th energy. A general model blend will be preferred. ...Pacific Northwest/Southwest Canada... ...Upper Midwest by Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 60 hours Non-NAM blend...after 60 hours Confidence: Above Average The guidance agrees in taking a positively tilted longwave trough across southwest British Columbia, Vancouver Island, and off the northwest coast and moving the wave northeast into central Canada over the weekend. The energy will then begin to dig a bit to the southeast and cross into the upper Midwest on Monday. The guidance is in good agreement with the overall evolution of this energy through the period with exception to the 12Z NAM which begins to outrun the global models with the timing of its closed low passing just southwest of Hudson Bay by the end of the period. A general model blend through 60 hours should suffice, followed by a non-NAM blend thereafter. ...Upper low/trough off the Pacific Northwest on Sunday/Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models take a portion of the energy traversing southwest Canada and pinch off a new trough/closed low just offshore of WA/OR by Sunday. The models are in reasonably good agreement with their positioning and depth of the system, and thus a general model blend will be preferred. ...Upper trough over the Gulf Coast/Southeast... ...Surface low development near the Southeast Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM/UKMET/ECMWF solutions Confidence: Average A broad upper trough over the Gulf Coast states and adjacent areas of the TN Valley and the Southeast will generally remain in place through the weekend and into early next week. There is minimal spread with the larger scale details of the trough, and so a general model blend will be preferred with this energy. Regarding the surface trough lifting up off the Southeast coastline, the models still favor some weak surface low development along it as the energy begins to turn northeast and out to sea to the east of the NC Outer Banks on Sunday. The 12Z NAM is the strongest solution with the 00Z ECMWF the weakest. A general model blend of the guidance should resolve the differences seen in the strength of the low for this period. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Orrison