... A potentially historic winter storm will impact the Tri-State area today into Monday. This is a dangerous situation with blizzard conditions expected to develop tonight.
All guidance has converged on the evolution, track, and intensity of the system. There are some subtle differences with the global models taking a 970 mb low close to the 40N/70W benchmark by Monday morning, while the hires models are slightly farther west. The latter could be the difference for even higher snowfall amounts than currently forecast.
Low pressure will quickly develop off along the North Carolina coast this morning and rapidly intensify this evening into Monday morning as it slowly lifts north-north east towards the 40N/70W benchmark. The 00Z ECMWF has come into better agreement as it has generally been on the eastern envelope of the operational guidance. This slight shift has resulted in the model QPF coming more into line with the current forecast. Forecast liquid equivalent amounts are mainly between 1.5 and 2 inches. Initially, snow ratios will start out 10:1 or even a bit lower today, then increasing to 12-14:1 by daybreak Monday as colder air wraps around the system. NBM snow ratios have been consistently too high through the event from start to finish.
While deep-layered lift in the snow growth region (-10 to -20C) favors dendritic growth and high ratios, high winds will likely result in fracturing of the crystals, lowering rates. Putting this all together, expect 1 to 2 ft across the tri-state. This is up a few inches from the last forecast.
On the higher end, the NBM (01Z) supports 23 to 30 inches across the area, due to a bit more QPF and the aforementioned higher ratios.
Its 90th percentile supports close to 3 ft across much of the area. The NAMNest is also on the higher end with 2 to 3 inches of liquid equivalent. This is likely due to its more westward track.
The 06Z HRRR which is similar in its track is very much in line with the current forecast. However, a reasonable worst case could put totals up to 3 ft. ...
