I like the looks of the storm on tap for late tonight and tomorrow. It's a pretty good front that is going to usher in the coldest air of the season so far for northern Utah.
We'll start with a look at the GFS forecast valid 0900 UTC 26 October (3 AM MDT Wednesday) when a compact upper-level trough is centered over southeast Oregon and the preceeding cold front is draped across northern Utah. At 700 mb, roughly 10,000 feet or crest hight of the Wasatch Range, there is about a 12˚C (22˚F) temperature contrast across this front, so it's a whopper.
By 1500 UTC (0900 MDT), the trough is over southwest Idaho and the front is draped over Salt Lake City. We will be post-frontal by this time with steady rain on the valley floor and snow intensifying in the mountains. Woo hoo!
By 2100 UTC (3 PM MDT), the cold air is into northern Utah in earnest with 700-mb temperatures over the Salt Lake Valley below -6˚C. This will mean some flakes down to bench levels.
The phasing of the frontal band with the coldest air is such that accumulations below 6000 feet will probably be limited, but I'd keep an eye on forecasts as such details are hard to anticipate with precision.
For Alta, most of the models are producing forecasts clustering around about 0.7 to 1.2" of water and 8-16 inches of snow. The latest HRRR generates a quick hitting frontal passage with precipitation beginning just before 3 AM tonight and ending by about 10 or 11 AM tomorrow, resulting in just over 8 inches of snow from about 1" of water.
The GFS, has somewhat different ideas on timing, with precip starting after midnight and continuing until the late afternoon. This solution would be more favorable for some flakes on the benches since the precip keeps going until the arrival of the coldest air. That said, the GFS produces a bit less precipitation with just over 8" of snow and about 0.7" of water.
The downscaled SREF is coming in with 0.5 to 1.5" of water with a mean just under 1". The snowfall range is around 7 to 17". There are a couple of members going for a bit more with a second trough friday night and Saturday, but right now I'm not expecting that to do very much.
Bottom line is this looks like an 6-12" storm for Alta. We may do a bit better if the front moves through slowly.
A look at the High Rustler cam this morning shows this will fall on dirt and grass on the lower mountain and on old snow from prior storms on shadier aspects (other aspects have melted out even at upper elevations).
Anyone skiing is going to experience the lowest of low tide conditions with plenty of buried and unburied hazards. I haven't been up to poke around the snowpack where it exists, but early snow often becomes weak snow, so be careful out there.
Been snowing up at Targhee since Wed.AM. Fun to watch on the cameras.
ReplyDeleteFYI - I think you might be confusing neap tides with spring tides. Neap tides have the lowest range between high and low, and in some areas result in nearly no tidal swing at all. Spring tides (which happen in every season) have the greatest range and will generally result in the shallowest low tides and deepest high tides at a given location.
ReplyDeleteLandlubber here. You are correct and it has been fixed. Don't tell my inlaws who are deep in the fishing industry...
DeleteNeap tides are four letter words to fishermen. At least nearshore fishermen. Surfers, too.
DeleteDay 3 in Collins Gulch today, Friday Oct 27 after Thursday storm.
ReplyDeleteI’ll skip the tide discussion to simply note there is a distinct lack of snow at the base making dedicated rock skis useful.
Being retired, 1 lap Spring Valley and 3 laps Ballroom, which has many rocks it is helpful to know the location of but also has grassy lines where I descended. Variable snow depth in Ballroom at 10300 elevation from wind drifting, 1 spot had 4 feet, a fluke, 18 inches seems average but could be optimistic. At least a foot. Not bad turning.
Main Chute got hit yesterday, which seems hard to believe, and moguled today. I’d say 50 people have skied it, which could be an exaggeration, but well more than 10, at least 20. A small sluff was released at some point running a couple hundred vertical feet. Would have been an unpleasant possibly season ending ride.
An adventuresome soul, presumably young and male with lots of testosterone and skill, negotiated the upper cliff bands to make a turning descent of Little Chute. This is actually impossible for me to believe.
Sadly, at least the beginning of our season is going to be plagued by basal weakness high north. If it starts storming and doesn’t stop this could be a bad memory by January. Here’s hoping.
We MUST PRAY for MORE SNOW, LESS WIND and LOWER WETBULBZERO with VERY MANY ICE NUCLEATING PARTICLES