Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 235 AM EDT Tue May 26 2020 Valid May 26/0000 UTC thru May 29/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Shortwave currently over the northern Plains Reloading northern stream trough over northern Plains by Wednesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average A shortwave trough currently over the northern Plains will be getting absorbed into the westerlies across southern Canada by later Tuesday. However, by later Tuesday and Wednesday, the models support amplification of a new northern stream trough over southern Canada and the northern Plains. This energy should then move across the upper Midwest by Thursday. This will drive 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 for the time being. Deep closed low over the southern Plains and lower MS Valley Weakening toward the OH/TN Valleys by Friday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 60 hours Non-CMC blend...after 60 hours Confidence: Slightly above average The models all agree in developing a cut-off upper low over northern TX by late Tuesday. This upper low should then drift very slowly eastward through northeast Texas by early Wednesday. On Thursday, it should cross the lower MS Valley, but the guidance supports it beginning to slowly weaken and elongate east-northeastward toward the lower OH/TN Valleys by Friday as it comes under influence of the northern stream trough crossing the upper Midwest. Model mass field spread is minimal through about 60 hours. After 60 hours, the 00Z CMC was seen as keeping the upper low south of the model consensus, but there is good clustering seen otherwise in the guidance to support the energy advancing into the OH/TN Valley region by early Friday. Will prefer a general model blend through 60 hours, and then a non-CMC blend thereafter. Mid-level trough and weak surface lows impacting Florida Energy lifting up across the Southeast U.S. by Wednesday/Thursday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS, 00Z GEFS mean and 12Z ECENS mean Confidence: Average An upper level ridge over the Southeast U.S. will gradually build out across the western Atlantic by midweek. South and west of the evolving ridge will be a low to mid-level trough axis which is expected to lift northward through the eastern Gulf of Mexico and the FL Peninsula going through Tuesday. By Wednesday and Thursday, this energy will be advancing north through the Southeast and the southern Appalachians within deep layer southerly flow situated between the deep upper low approaching the lower MS Valley 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 forming near the east coast of FL. The one along the east coast of FL is expected to develop near the Melbourne area early Tuesday and lift north to coastal areas of GA and SC going through Wednesday before then advancing inland. The 00Z NAM and 00Z GFS are perhaps just a little faster than the non-NCEP models in taking the low northward. Overall the 00Z UKMET was seen as being the slowest, but it also still is perhaps a little too slow to advance its mid-level trough north as well into the Southeast. In time, the 00Z NAM becomes somewhat of a stronger outlier with the mid-level trough as it lifts north through the Southeast and into the southern Appalachians. The 00Z GEFS mean and 12Z ECENS mean both tend to support the slightly more progressive/northerly consensus with the mid-level trough and FL east coast surface low. So, the preference will be toward a blend of the 00Z GFS, 00Z GEFS mean and 12Z ECENS mean for the time being. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison