Don't know anything about exactly where the XC trails are in the Tahoe area. Vaguely remember that one recent season there was supposed to either training or perhaps even a race and there was very little snow. A friend's son is a XC coach.
Tony Crocker's recommendations for Christmas vacation ski trips don't rate Tahoe that highly. He wrote "Sierra snowfall is abundant but volatile, so about a quarter of Christmas seasons are pretty awful, with minimal natural snow base and much less than half the terrain skiable. Conversely, the best holiday seasons feature midwinter conditions on deep snow bases of 100+ inches. Last-minute decisions can thus be well rewarded."
I wrote that article 17 years ago but it's still applicable.
Cross country trails don't require a deep base, but they also tend to be at low altitude where early season rain is more of an issue. I suspect cross country areas don't make snow.
That article is the best way I know how to help families or teachers stuck skiing during school holidays.
Got curious. I know Mt. Van Ho invested in Snow Factory to make sure there was enough snow for early season training and racing. Looks like there are a few places out west that have invested in more traditional snowmaking. This article dated Nov 2017 mentions nordic centers at Breck and Frisco in Colorado. Lots of nordic centers in the northeast with snowmaking. I know there is snowmaking in Scandinavia for nordic skiing.