Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1155 PM EST Fri Jan 31 2020 Valid Feb 01/0000 UTC thru Feb 04/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Evolution of Trough over Eastern Half of the U.S. through Sunday... ...Coastal low tracking north offshore of New England late Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ Preference: General model blend Confidence: Slightly above average Models were still making some run to run shifts in terms of how much energy will be part of the northern stream portion of the mid-level trough that affects parts of the Northeast later this coming night. Downstream of the trough axis, surface cyclogenesis is expected to occur off of the Mid-Atlantic or New England coast later today. The GFS was still a bit stronger than the UKMET while the Canadian was more amplified resulting in the base of its trough being deeper and more southerly. Thinking is that a blend of the 01/00Z GFS and NAM with the 31/12Z ECMWF will work to minimize some of these differences and maintaining a middle ground. Regarding the offshore surface low, there is good agreement with track until the low is offshore of Nova Scotia, with a GFS/ECMWF blend working well for both position and timing. ...Pacific Northwest atmospheric river leading a longwave trough pushing into the West on Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of non 12Z GFS guidance Confidence: Average There is reasonable agreement with the evolution of a longwave trough across the West Coast into the Great Basin into early next week. There 01/00Z GFS maintained continuity with its previous run, which meant that it remained a bit quicker than then model consensus with the leading edge of the trough by early Sunday. Model deterministic models cluster better with the 31/12Z ECMWF and UKMET. A non 12Z GFS blend of guidance looks reasonable for the western U.S. trough since differences among the non-GFS deterministic guidance are minor. ...Leading shortwave tracking through southern Canada on Sunday with accompanying surface low... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average Weak height falls moving eastward across southern Canada on Sunday and Sunday night be accompanied by a weak area of low pressure at the surface. The 01/00Z GFS remained a bit faster than the 31/12Z ECMWF...with other guidance in reasonably close proximity. Still think that the model differences are small enough that a general model blend should work. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Bann