That is both my forecast and the official forecast. On the subject of the official forecasts, they are usually pretty good, and usually the same forecast I would give, were I a professional weather forecaster. The times I make a big stink are the times the official forecasts don’t make much sense to me.
Anyhow, if you’re planning outdoor activities, Saturday definitely sounds like the better day. The source of the moisture that will make Sunday (and the beginning of the work week) so wet is coming out of the tropical Pacific, so it will drag some relatively warmer air up our way with it. Expect some high temperatures in the fifties, maybe well into the fifties (Bellingham is often one of the warmest spots in Western Washington when a strong south wind is blowing, more on why that is the case sometime later).
That means snow levels will be rising, though at this time it seems likely they will stay (just) below the elevation of the Heather Meadows area. Still, if I were skiing, I would opt for Saturday. Some light snow which is drier because temperatures are still reliably below freezing sounds a lot nicer than copious amounts of heavy, wet “Cascade concrete” snow.
This will likely prove to be just a temporary mild interlude to a generally cool pattern that we are for the next several weeks. The long-range models have all been consistent with things staying on the cool side at least through the first half or March.
This also means that we’re not out of the woods quite yet when it comes to lowland snow; yes we can get lowland snow in March, sometimes significant amounts of it. I must emphasize, however, that at this time there is no specific indication of any such thing. The dice are merely loaded so that outcome has a higher chance than normal, that is all.