Forecast:
Saturday (12/14): Snow, highs in the upper 20s, westerly winds at 10-20 mph with gusts to 40 mph.
Sunday (12/15): Light snow, highs in the upper teens, westerly winds with some gusts in the morning, with winds and snow decreasing during the day.
Forecast Discussion:
This is an somewhat unusual storm, but it’s producing snow so I like it. As you may know, our patrol backcountry area tends to get snow in one of three ways, in descending order of importance. (1) A favorable wind direction (east is best) coupled with moisture creating orographic lift. (2) A strong enough storm from an unfavorable direction (for example, from the west) so we fall within the spillover effect. (3) Bands of snow caused by jet streaks or other upper atmospheric phenomenon. What makes this storm interesting and complex is that it is almost entirely fueled by #3 – that is, the speed of the jet streak overhead (with a little bit of #2 added into the mix). So look straight up about six miles, and say thank you to the upper atmosphere for providing the lift to give us snow.
It’s very hard to predict the snowfall from a storm formed by jet streaks. Don’t take my word for it – rather let’s look at how insanely different the major models were (and are) calling this storm. As of the Thursday afternoon model runs (that is once the storm was already starting up), here are what the models were each saying:
- The CAIC WRF Hi-Res was calling for 19” as the storm total at Eldora, with snow starting on Thursday evening and going to Saturday evening.
- The American (GFS) model (grid over Eldora) was calling for 11” as the storm total, with snow starting Thursday evening and going through mid-day Sunday.
- The NAM model (grid over Eldora) was calling for 9” as the storm total, with snow starting Thursday evening and going through Sunday afternoon.
- The Canadian (GDPS) model (grid over Eldora) was calling for 2” as the storm total, with snow starting Friday morning and going through mid-day Monday.
As of 9:30 am this morning (Friday), Eldora has already picked up 10” of snow total from this storm, with similar reports on the other side of the divide. Yeah! So, although we’re only a third of the way time-wise into the storm system at the time of this forecast, I think we can safely declare the CAIC WRF Hi-Res Model as the winner among the models. Sorry Canada – thankfully you called this one pretty far wrong! Even the American (GFS) and NAM were pretty wide of the mark, as they both had only predicted 2” of snow by mid-morning today.
If we keep our money on the CAIC WRF Hi-Res for the rest of the storm, it’s calling for 14 more inches between late Friday and early Sunday morning. The American (GFS) Model and the NAM are both calling for 5” more, with the Canadian (GDPS) calling for 1” more. I’ll put my money on the CAIC WRF Hi-Res, even if it may be a tad optimistic.
Looking ahead, next chance of snow comes next Thursday and Friday (12/19-12/20) per the American (GFS) Model, but it doesn’t look too big. Beyond that, the American (GFS) Model is calling for another (and possibly bigger) round of snow starting Christmas Eve. Of course, the Christmas storm is far enough away to be (fittingly) in forecast fairyland.
As an aside, as I mentioned last week, the avalanche situation is currently very complicated. By way of example, there was a skier triggered avalanche on No Name at Berthoud Pass on December 11. I know the avalanche path very well, and it slid in a very different pattern than normal. The Bench also slid at Berthoud, but in a typical slide pattern. With this new snow, expect avalanche conditions to be both really bad and really complex. Not a good combination.
Thanks for your patience in this longer than normal post, and as always, please let me know your thoughts on the post and what you see this weekend.
-Jordan (Friday morning)
