Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1215 AM EDT Sun Jul 5 2020 Valid Jul 5/0000 UTC thru Jul 8/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Initial Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Trough building over the Northeast U.S. this weekend ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average The next shortwave trough in northwest flow is forecast to amplify some over northern New England by late Sunday with an upper low becoming likely by Monday across Nova Scotia, followed by low amplitude upper ridging arriving from Quebec early in the week. Models in the low-mid levels are in good agreement through Monday evening, after which the NAM becomes a bit more amplified. At the jet stream level, the 18Z and 00Z GFS are a little more progressive with the trough axis, but still close enough to be part of the model blend. A general model blend should work well for this region. Trough/weakness over the Gulf Coast region ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend Confidence: Average A rather broad weakness in the larger scale upper ridge across the Deep South and Southeast U.S. should remain nearly anchored in place through the beginning of the week, with a hint of a weak upper low trying to develop by Monday across the central Gulf Coast region. Remnant MCVs and convectively enhanced shortwaves are expected to be present within this broad trough, along with a weak surface frontal boundary. The main model difference noted here is a weaker and farther west solution with the 12Z UKMET, owing to a much stronger ridge across the central U.S. that falls outside the ensemble spread by Tuesday. Trough with multiple shortwaves across the Pacific Northwest and Canada ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: NAM/GFS/ECMWF blend Confidence: Above average General troughing is expected to continue across the Pacific Northwest and northern Rockies through the forecast period with a few separate shortwave troughs moving through the flow. One currently is lifting across the northern Rockies and then track across south-southern Canada. Followed by brief interim low-amplitude ridging, another shortwave trough reaches Oregon/Washington Monday afternoon. A third perturbation enters the offshore waters of the Pacific Northwest by Wednesday morning with the core of the upper trough remaining anchored over western Canada. The UKMET becomes weaker with the first shortwave by Sunday night across Saskatchewan and Manitoba, whilst becoming a little more amplified with the second shortwave. The CMC is noted as a much weaker solution across the Pacific Northwest by Monday night across the Pacific Northwest, and slower with the arrival of the third offshore system. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hamrick