I tend to be chronically conservative in reporting snow conditions in order to put a dose of reality into what we normally see published. Therefore when someone asks, "What is it going to be like a month from now?" I'm inclined to consider plausible worst case scenarios.
In the case of the Northeast the only correct answer to the above question is "I have no idea." Last Christmas one big rainstorm turned the conditions from epic to marginal in just a couple of days. And since rain is always possible back there, month-ahead predictions are not worth much. You can say the same thing here in SoCal, where sustained dry spells are common and the altitude is marginal for snow preservation.
In the case of Utah's Cottonwood Canyons rain is an extreme event, drought means 1/3 of normal snowfall worst case, and snow preservation is pretty good. Utah is the warmest region of the Rockies, so the worst case is probably a drought combined with a melt/freeze. Put Christmas crowds on top of that and you could get disappointing conditions, as were reported in January 2002. Starting with the current stellar situation I'd guess the odds of that are no more than 10% though.
The major caveat with Utah is that the Cottonwood Canyons have a unique and incredible microclimate. It does not apply to other Utah areas, which have both lower elevation and substantially less snowfall. The Canyons reports 42 inches season snowfall vs. 115-130 in the Cottonwood Canyons. Park City's snow numbers are taken from Jupiter Bowl and are not representative of at least 80% of the terrain. When The Canyons and Park City open this weekend, check what percent of runs are open as a comparison.
In the case of the Sierra, the question to answer is "What happens if there is NO snow at all for the next month?" At Mammoth, which has nearly perfect snow preservation characteristics, I have skied after a one month total drought and still had 50+% dry snow/packed powder in the ungroomed steeps plus excellent grooming of the intermediate runs. At Tahoe you will get numerous melt/freeze cycles and snowpack deterioration below about 8,000 feet during a sustained drought.
Based upon the current start, I would predict excellent holiday conditions at Mammoth, Kirkwood, Brian Head and the 4 Cottonwood resorts with a high degree of confidence. Areas like Squaw and Heavenly will have good upper mountain skiing even if the lower elevations deteriorate. The same may be true for the Park City group, but it's hard to tell until they open.
Elsewhere in the West there has not been enough natural snow yet to make any predictions about December conditions.
