Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 246 PM EDT Tue May 26 2020 Valid May 26/1200 UTC thru May 30/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation Including Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Overall Pattern across the continental U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Moderate-High A shortwave trough currently over the northern Plains will be getting absorbed into the westerlies across southern Canada by Tuesday night. By Wednesday, the models support amplification of a new northern stream trough over southern Canada and the northern Plains, and then move across the upper Midwest by Thursday. This will support surface low pressure across southern Canada with a trailing cold front that will be crossing the northern Plains and upper Midwest. The model spread through the period is rather modest, and so a general model blend will be preferred. Across the south-central U.S., the models all agree in developing a cut-off upper low over northern Texas by late Tuesday. This upper low should then drift very slowly eastward across the ArkLaTex region by Wednesday. On Thursday, it should cross the Mid-South, but the guidance supports it beginning to slowly weaken and elongate east-northeastward toward the lower Ohio and Tennessee Valleys by Friday as it comes under influence of the northern stream trough crossing the upper Midwest. Model mass field spread is minimal through the majority of the forecast period, and then the NAM and GFS remain more amplified than the non-NCEP guidance for the day 3 period. To the south and west of the evolving ridge East Coast ridge will be a low to mid-level trough axis which is expected to lift northward through the eastern Gulf of Mexico and the Florida Peninsula going through Tuesday evening. By mid-week, this energy will be advancing north across the Southeast and the southern Appalachians within deep layer southerly flow situated between the deep upper low approaching the Mid-South and the building ridge over the western Atlantic. Multiple waves of low pressure are expected to evolve with this system with one low lifting north across the eastern Gulf of Mexico, and another near the east coast of Florida. The one along the east coast of Florida is expected to lift northward to coastal areas of Georgia and South Carolina going through Wednesday before then advancing inland. With the exception of the 12Z ECMWF that is west of the model consensus with the low near the southeast coast, the models appear to be in relatively good agreement. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hamrick/Orrison