All Hail Lindsey Vonn!

Source: AP Photo/Luciano Bisi

It's easy to become cynical about sports these days, but there are some athletes who deliver performances that are truly uplifting and inspiring.  

Lindey Vonn winning the World Cup in St. Moritz on Friday is one of the most remarkable and astonishing performances I can think of in skiing if not all of sports.  

Before Friday, the oldest woman to ever win a World Cup race was Federica Brignone at the age of 34.  Brignone herself is a force of nature and one of my favorite skiers as she sends it with such passion (she is currently recovering from a major knee injury and I am hoping will return for the Olympics).  Vonn is 41. 41!  

Most of you know her story.  She won in every discipline on the world cup and fell just short of what was then Ingemar Stenmark's record of 86 world cup winds with 82 when she retired.  She is unquestionably the greatest speed skier of all time.  

She retired in 2019.  A knee replacement and a hell of a lot of hard work later, she is on top of the world, with Stenmark in her sights again (although she won't catch Mikaela Shiffrin), not to mention a shot at Olympic gold in Cortina.  

Simply incredible.  

Whither the Start of Ski Season

Sigh...what a start to December.

First let's have a look at the northwest storm.  Some bit water totals so far.  For the 3-day period ending at 6 AM PST/1200 UTC today (11 December), more than 10" of liquid precipitation equivalent at many sites in the Washington Cascades including 14.2" at Paradise SNOTEL (agreeing well with the expectations from the previous post) and 18.6" at the Lynn Lake SNOTEL between Paradise and Snoqualmie Pass.

Source: https://www.weather.gov/wrh/hazards

Crystal Mountain is reporting this morning that WA-410 is closed between Enumclaw and Greenwater, essentially cutting them off given that WA-410 is also closed over Cayuse and Chinook Passes to the south.  Most of their web cams are down but sadly, even at 6800' at the top of the Green Valley Express where a cam is working, it looks like a net loss from this storm.

Source: https://www.crystalmountainresort.com/the-mountain/mountain-report-and-webcams/webcams

Could be worse.  Below is the Summit West cam from Snoqualmie Pass.

Source: https://www.summitatsnoqualmie.com/webcams

Meanwhile in northern Utah, December continues to be the new October with yesterday's high of 61 at the Salt Lake city International Airport the average high on October 25.  

I keep thinking how fortunate we are that this low-amplitude ridge developed in a way that we stayed relatively mild at low levels.  If there had been a strong cold pool in place over the valley earlier this week, we would probably be much cooler.  If we can't have snow, then we may has well have a mild conditions in the valley.  We were also fortunate to have that storm last Friday Night and a few days of good snowmaking conditions before the warmth returned.  

A look at the ensembles shows a few members flattening out the ridge just enough to bring some precipitation into northern Utah the middle to end of next week.  An example is the ECMWF HRES. Forecast below for 1800 UTC Thursday 18 December.  

Indeed, for Alta-Collins the Utah Snow Ensemble has a few enthusiastic members, although most of the forecasts are still in the low-end snowfall range and most are warm through the 10-day forecast period.  

Median total water equivalent and snowfall are 0.91" and 8.0" through 5 PM Saturday 20 December, so we will set that as the over/under.  

Now is the time to burn skis.  I'd suggest human sacrifice, but some of you might just take that quip seriously. 

The Northwest Deluge

I've mentioned in prior posts that the storm track will be just to our north over the next several days.  Indeed, the Pacific Northwest is in for a deluge as they are raked by a series of storm systems.  Below is the Utah Snow Ensemble forecast for the 10-day period ending 0000 UTC 18 December.  Ensemble mean (upper right) liquid precipitation equivalents above 9" for most of the Cascades from Mt. Hood to Canada.  

It's worth a look at the plume for Paradise Ranger Station on Mt. Rainier, one of the wetter locations in the Cascades.  The ENS mean is > 20" over the 10 day period with the GEFS mean > 15".  There is tight clustering over the first 5 days of the forecast with most ensemble members between about 12.5 and 17.5".  We see a lot of spread in the ensemble forecasts sometimes, but this is pretty tight clustering for a major events.  

The ensemble grid point for Paradise is at 4942 ft, which is a bit lower than the actual ranger station (~5400 feet), but over the first five days from all of that water most ensemble members are only producing up to 20" of snow.  Rain rather than snow for much of the period.  What a waste of water. 

It's already a sad picture at Crystal Mountain today.

Source: https://www.crystalmountainresort.com/the-mountain/mountain-report-and-webcams/webcams

Worth watching forecasts if you are in the Northwest.  

The Europeans and Americans Simply Cannot Get Along

The overnight Utah Snow Ensemble forecast for Alta-Collins may be the crazies I've ever seen.  Most of the European Ensemble (ENS) members are producing little to no precipitation over the next 10 days including during during the period from 10-11 December (more on those dates in a minute).  The wettest ENS member puts out about 0.8" of water and 11" of snow.  

Some members of the American Ensemble (GEFS) have very different ideas.  There are 31 GEFS members and 10 of them put out more than 1.5" of water just through 00Z 12 December.  Several more put out between 1 and 1.5" of water.  There are some that track with the ENS (hard to see but they are there), but many GEFS members are much wetter.

What gives?

I don't plot or attempt to look at forecast plots like our four panel synoptic diagnostic for all 82 members of the Utah Snow Ensemble.  Nobody has time for that.  So I'm going to start here with the ECMWF HRES forecast that serves as the ENS control and is valid 0000 UTC 11 December.  This forecast captures many of the salient details of the pattern that is going to prevail over western North America the next few days.  A broad, low-amplitude upper-level ridge is centered near the Pcific coast (upper left) with an atmospheric river rolling over this ridge and across the northern US Rockies (lower right).  Heavy orographic precipitation occurs where the atmospheric river crosses major western mountain barriers.

So in the HRES the central Wasatch is just to the south of the action.  There are a few dribs and drabs that make it in, but accumulations are scant.  Most ENS members have a similar forecast.

Some of the GEFS members, however, shift the storm track far enough south to get us in on the action.

Diagnosing the why this occurs in this case is beyond my abilities.  I'll just say that I lean heavily toward the view that the central Wasatch may see some dribs and drabs over the next week but it's unlikely we'll see the game changing major accumulations that we need. 

Mother Nature Delivers the Concrete

Twenty-four hour totals at the Alta-Collins automated observing site added up to 1.79" of water and 15" of snow, yielding a mean water content of 12%.  Snowbasin-Boardwalk came in with 1.26"/8"/16%.  As evidence of the wet, windy, and rimey nature of the storm, I couldn't verify our 70 mph forecast for Mt. Baldy because the sensor rimed and is no longer spinning.  The Utah Avalanche Center report this morning says that "at 11,000 feet the wind is absolutely ripping, with sustained speeds at 50–60 mph with gusts pushing into the upper 70s."  That's good enough for me.  

The Alta-Collins snowstake photo this morning is one of the most comical I've ever seen.  Dense snow apparently carved by wind?  Perhaps with the flow wrapping around the Alta sign?  Who knows.  Come up with your own explanation.  

Snowfall at lower elevations is certainly lower and probably a soggy mess between 6000 and 7000 feet (or higher), but that's just a guess.  

The Cottonwoods might get a bit before things taper down later this morning.  The extended forecast shows that you should continue to root for America.  The European Ensemble (ENS) is giving Alta practically nothing after today.  The American (GEFS) is more generous around the middle of the work week.   

USA. USA. USA.

Friday Morning Update

In the previous post (Windy Storm on Tap) we discussed an approaching storm system that would come in today (Friday), but really pick up Friday night as strong flow and an inland penetrating atmospheric river move into northern Utah. 

That forecast is still on track.  Overnight last night and today we are seeing the dribs and drabs at the leading edge of the storm system, as expected.  Overnight through 8 AM this morning Alta-Collins picked up about .16" of water and 2" of snow and Snowbasin-Boardwalk came in with 0.24" of water and 3" of snow.  

But the big story is not today but tonight when the precipitation efficiency looks to increase as an upper-level trough moves through and high integrated vapor transport (IVT) noses into northern Utah.  The GFS forecast valid 0600 UTC 6 Dec (11 PM MDT Friday) shows heavy precipitation over the mountains of northern Utah (or better put what the GFS thinks is the mountains of northern Utah) as the trough (dashed line below) as the trough moves through.  

Our HRRR-derived forecast for upper Little Cottonwood (click to enlarge) shows relatively light periods of precipitation through 5 PM today (top left), afterwhich hourly liquid-precipitation equivalent rates really pick up as the upper-level trough approaches.  Precipitation rates maximize at around 1 AM Saturday with periods of precipitation continuing through 7 AM tomorrow (Saturday) after which precipitation becomes widely scattered.  

This is a warm and windy storm.  Our forecast winds for Mt. Baldy peak at around 700 70 mph [Apologies for the typo! - Jim] at 4 AM Saturday.  Temperatures overnight are forecast to be around 27 F at Collins and 30 F at the base.  As a result, snow-to-liquid ratios are low and generally less than 10 for the period.  This keeps the HRRR-derived snowfall relatively low and around 13" including the dribs and drabs today.  That said, at this point with the need for base, Cascade Concrete is better than Cold Smoke. 

The overnight six-member RRFS ensemble shows a range of liquid precipitation equivalent of between about 1.1 and 2.3" and snowfall between about 13" and 26".  Thus, the HRRR is on the low end of the RRFS.  

My take is that 1.2-2.2" of water and 12-22" of snow from 7 AM this morning through 7 AM Saturday represent the most likely range of outcomes for Alta-Collins, with much of that coming this evening and tonight.  The water amounts are most important right now to build base.  Let's hope we can eclipse 2".

Looking to the north, the story at Snowbasin is much the same with the overnight period being the wettest and then things settling down towards morning.  Snow-to-liquid ratios are quite low at Boardwalk, which is lower than Alta-Collins and thus warmer in this storm.  I'm expecting this to be a very wet snow event up there.  

The HRRR Skew-T for Ogden shows a freezing level near 775 mb or about 7000 ft.  Conditions are saturated, so that also represents the wet-bulb zero level.  

If we zoom into the plot of wet-bulb zero height with time we see that it just about reaches the altitude of boardwal (~8000 ft) and after midnight the base is below that level.  This raises the possibility of a bit of rain or mixed rain and snow at the base depending on how things shake out.  

The extended forecast after this storm is not great for us, but maybe we can get something.  The GFS, for example, has a monster atmospheric river roaring across the northwest next week.  Batten down the hatches for the Cascades, and mountains of the Idaho Panhandle, Montana, and northwest Wyoming.  Goodness gracious that is a tempest of a forecast for them.  

We're to the south of most of the action.  Best case scenario is we get some storms to dip into our area and get some modest accumulations.  Worst case is we don't get much at all.  Odds favor below average precipitation next week, but if the storm track can dip a bit further south than currently forecast, we could get something.