Monday, March 23, 2015

A Brief Flirtation with Spring Showers

Every couple of weeks Mother Nature allows a storm or two to slip through the net and give us a brief break from the death ridge.  One of those storms is here this morning as a cold front is sweeping across northern Utah bringing valley showers and mountain snow showers.  We'll then have a break later tonight and Tuesday, with another front coming in Tuesday night, after which the death ridge returns.

Two fronts sounds exciting, but this really isn't a major storm cycle by old-fashioned Utah standards. In the upper Cottonwoods, the NAM is generating about .3 inches of water and 4 inches of snow today and tonight, with another .2 water/2 inches of snow with the front on Tuesday night (see lower two panels below).

My usual approach in the winter is to use the NAM as the low-end of the forecast range for Alta, but such an approach doesn't typically do as well in the spring when storms on average feature less orographic enhancement.  In addition, this looks like a pattern where showers will be hit or miss.  In other words, if you don't like the weather, wait 5 minutes.  As such, I think a total of 3-6" today and tonight is probably reasonable, although I won't be surprised if we come in a bit below or above that given the showery nature of the pattern.  Yes, there is a chance of thunderstorms too, which would make may day.  Looks like rain for the valley, unless we get a very strong shower and then perhaps we'll mix in some graupel or ice pellets.

We'll get a little more with the second front.  Maybe in total the two events will give us something in the 5-10 inch range in the upper Cottonwoods.  Not much by old fashioned standards, but a blizzard by contemporary standards...

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