Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 222 PM EST Mon Feb 24 2020 Valid Feb 24/1200 UTC thru Feb 28/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Closed low and its interaction with an upstream amplifying northern stream wave across Plains/Great Lakes through Tuesday... ...Associated surface low crossing the Mississippi River and into the Great Lakes Tue/Wed... ...Developing East Coast low Wed night.... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 27.00Z, 12Z ECMWF/UKMET/GFS blend thereafter Confidence: Average to slightly below average after 27.00Z 19Z update: The ECMWF continued its trend a bit to the south/southeast with the upper level energy across portions of the Midwest for day 2 and remains on the weaker/less deep side compared to the GFS. The ECMWF is also fairly similar to the UKMET position with the 500 mb low, which seems to be where the GFS is trying to trend to. So the blend preference was updated to go with a GFS/ECMWF/UKMET blend after 27.00Z. Weakening upper level low currently over portions of the southern Missouri Ozarks will fill as it slowly moves eastward. A digging shortwave trough over the northern Rockies seen in the latest water vapor imagery is forecast to dig toward the mid-MS Valley, reinforcing the upper level energy/trough over the central US through Tuesday/Tuesday PM. This idea is well agreed upon by the latest global model guidance such that a general model blend through 26.00Z can be utilized. Beyond that time frame, the forecast becomes less agreeable as several waves of low pressure track from the lower Ohio Valley, Great Lakes, and eventually up the East Coast. The initial wave of low pressure is forecast to move from southern MO to southern IN and western OH before dissipating by 26.12Z. The approach of the secondary upper level low acts to redevelop this feature and deepen it as moves through the eastern Great Lakes. Meanwhile, another surface low develops across the Mid-Atlantic and tracks along the East Coast into New England. The exact timing and phasing of all these features is messy and less certain and the ensemble low track plots show quite a bit of variety beyond 60 hours (27.00Z). The preference has been toward a more suppressed, southward adjusting system/track which has been the idea supported by the ECMWF over the last several model cycles. The 12Z GFS, while still on a north/northwest bias and also faster, but has been trending toward the ECMWF. The GFS also been advertising a deeper/stronger upper level low over the lower Great Lakes mid-week, while the ECMWF has been weaker. Both operational runs are in lock step with their respective ensemble means, they just have some variable timing differences. Overall, the preference is toward a ECMWF like solution though some components of the GFS look plausible so after 60 hours, a blend of the ECMWF/GFS seems like a good approach at this time. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor