Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1147 PM EST Sun Feb 17 2019 Valid Feb 18/0000 UTC thru Feb 21/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation...with Preferences and Confidences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Exiting shortwave/Coastal low development through Monday evening... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Current surface low over southeast Ohio will weaken as it moves northeast and will be followed by a coastal low developing off Long Island by early Monday. That low will then quickly move northeast. The axis of precipitation across the Great Lakes and Northeast will shift and pull away by Monday evening. There is above average model agreement with the track and speed of the surface low between the available 00z and previous 12z guidance. ...Remaining CONUS/Western Trough Ejecting Impulses into Midwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 20.12z 12z ECMWF/CMC, 00z GFS/NAM blend after Confidence: Average The general pattern through the week across the CONUS will feature a Western US trough with southwest flow through the central/eastern US anchored by subtropical ridging over Florida. Through the period, several impulses will eject out into the Plains, the first being Tuesday night through Wednesday evening. There is fairly good model agreement through 20.12z and as such, a general model blend can be used. After that time period, some differences are noted. The 00z NAM is considerably stronger ejecting the mid-level shortwave trough into the mid-MS River Valley and lower Great Lakes Wednesday into Wednesday night, almost closing off the mid-level feature. It is also on the faster side of the model spread. At the surface, low pressure will form across the Gulf of Mexico and then lift northward into the TN Valley. High pressure anchored over southeast Canada will likely create favorable cold air damming conditions east of the Appalachians, which is well represented by the operational models. The biggest variations in the models in this time frame will be due to convective issues leading to spatial differences in the maximum QPF. In the Tuesday night into Wednesday period, the greatest axis of rainfall looks to fall along the mid-MS River Valley into the TN and lower OH Valleys, and the GFS/NAM/ECMWF all represent this fairly similarly, through the ECMWF is further south. The outlier is the CMC, which is further east (with separate maximums over TN/NC) while the UKMET is a tad west (more across AR). The trend has been westward, though very slightly. With this in mind, a non-CMC blend is preferred here. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina