"Covember" Doldrums

November 2020.  A month better called "Covember" given the explosion of COVID cases across the country.

For Salt Lake Area skiers, the month started out with promise with over 50 inches of snow at Alta.  Since then, however, the Covember doldrums have settled in.  Yesterday I found both overcast and "undersmog" as I walked in the Avenues foothills.  This is not an uncommon scene this time of year when a weak trough and associated warm-air advection move through the area.  Such a situation increases the stability and provides just enough lift for mid-level cloud formation, but insufficient moisture and flow to generate precipitation or scour out the stable airmass over the valley.  

If you had asked me a few days ago about snow potential Thanksgiving week, I wouldn't have been excited, but I probably would have thought we'd do OK.  Two troughs were forecast to move through the area, so we'd be bound to get something.  In a case of snatching defeat from the jaws of victory, the latest models continue to bring those troughs through, but provide the Wasatch with paltry amounts of precipitation.  The GFS loop below shows the passage of the two troughs.

The SREF forecast for Alta below does a pretty good job of summarizing the suite of solutions being put forth by the various modeling systems.  Most are calling for light accumulations from both trough passages.  Of the 26 SREF members, 23 produce 3" or less from the first trough and only one produces more than 7" from both.  

Thus, unless there's a big surprise, dust on crust or dirt, depending on elevation and aspect. 

When Were the "Good Old Days"?

A lot of people ask me why it seems to be that we never get a good start to the ski season in November.  We all have memories of good starts to the ski season.  Certainly it was better in the "good old days."  But was it?

We have relatively short records of November snowfall in the Wasatch Range.  There are actually records for Silver Lake/Brighton going back to 1916, but there are a large number of missing days prior to 1942, in some intermediate years, and then again since 2000.  Thus, I'm going to use Alta Guard, which has a shorter but more continuous record of November snowfall, with only 1972/73 missing.  

A look at the November snowfall shows three fairly distinct periods (the plot below is labeled by season, so 1945/46 denotes November 1945).  Pre 1982/83, 1982/83 to 2003/04, and post 2003/04.  The middle period of from 1982/83 to 2003/04 is the fat period when there is a high frequency of heavy November snowfalls and the six largest November snowfalls on record.  The running five-year average (black line) was near or even above 100 inches during the middle of the period.  For many people, I think these are the "good old days".

But those years were not reflective of most of the record.  For the pre-1982/83 period, the five year running average was between about 45 and 70 inches.  From 1953/54 to 1963/64 it was near 50 inches.  That ten year period compares well to the 2008/09 to present period when we've been running around 50 inches.  Maybe the old days weren't really so good?  

For kicks and giggles, the red line is a linear trend line on the snowfall.  It has a very slight downward trend that I suspect is not statistically significant.  It sometimes makes sense to use linear trends, but for snowfall, which exhibits a great deal of year to year and even decade to decade variability, linear trends over such a short period of record make little sense.  The fat years in the middle were not the result of a long-term trend, but instead what meteorologists refer to as decadal-scale variability, something that is very apparent if one looks at paleoclimate records over the western United States, such as tree rings, which show slow decadal-scale variations from wet to dry periods.  Our instrumented record for the Wasatch Range is too short to identify these.  The period from 1982/83 to 2003/04 (give or take a few years at the end) is one of the wet periods. 

A critical question, however, is whether or not our recent string of poor November snowfalls reflects something new, namely human-caused climate change.  Alternatively, are the odds of poor November snowfalls increasing due to human-caused climate change?  

I don't have the time to answer that question today, but if you want some insights, see some of my older posts:

• Western Snow Trends and Global Warming: Part I
• Western Snow Trends and Global Warming: Part II
• A Look at Snowpack Trends

Windy and Insanely Warm

So far this month, Mother Nature has fulfilled half her bargain.  She's given us snow, but instead of light winds, she keeps giving us tempests.  

Crest level winds over the last 7 days in the central Wasatch show winds with gusts at or above 50 mph have predominated about half the period.  On Saturday, the ridge tops in some areas saw gusts to nearly 100 mph, whereas this morning we've seen gusts to over 70 mph.  

This is no way to maintain decent skiing.

The situation overnight and this morning is one with strong, large-scale, southwesterly flow over Utah.  The GFS analysis for 0600 UTC (11 PM MST) showed 700-mb winds of more than 50 knots over portions of western Utah (lower left panel) and a strong sea level pressure gradient and southerly flow at the surface (lower right).  

In that southwesterly flow, there's a nice orographic cloud sitting over the central Wasatch this morning.  Sadly, it does not appear to be producing any snow.

This morning's 1200 UTC (5 AM MST) sounding from the airport is, how shall I put this, absurd.  Before you take a look, let me remind you that it is November 18 when the average high temperature is 48˚F.  

The sounding shows a surface temperature of 65˚F.  There's practically no surface inversion that typically develops at night.  Instead, very strong southerly flow has kept the atmosphere "well mixed" as we say in the meteorological business.  The wind profile shows a low-level jet with a peak wind speed of 45 knots at about 800 mb.  Winds actually decrease above that level up to 700 mb.  

Since midnight, the lowest temperature recorded at the airport was 59˚F.  That just seems ridiculous, and it is.  The highest minimum temperature on record at the airport for Nov 18 is 48˚F in 1920.  

However, daily records are based on a 24-hour period, I believe from midnight to midnight standard time.  The minimum for the 24 hour period will probably not be 59˚F when we get to midnight tonight.  The models call for a weak cold front to move through later today.  Note in the HRRR forecast below for 0000 UTC (5 PM MST) the northwesterly flow over the Salt Lake Valley and Great Salt Lake Basin.  

That will probably drop our temperatures down into the low 50s or high 40s by midnight tonight.  Thus, we still have a shot at the highest minimum temperature for the day, but 59˚F is probably not going to hold.  

On the bright side, perhaps the valley single track is drying out.  

Skis of Seasons Past

Mother Nature has given us enough to start the ski season this year in November, but we're still dealing with low tide conditions.  

I'm skiing on some classic old skis that I prefer to think of as skis of seasons past rather than rock skis.  Specifically, I'm on a pair of Kahru Jak BCs that I think I bought in 2005.

These skis were ahead of their time.  Light and lively.  124-90-113.  I think this was the first setup I had with tech bindings.  I have a friend who used to tell me if I ever wanted to sell them to give him a call, although this year he suggested they belong in a museum.  That's a bit cruel.  I skied them today and I had FUN, although I need to take a closer look at the bindings, which may finally be on their last legs.  

I've been debating whether or not to buy equipment this year.  My "new" gear is about 4 years old and has some decent mileage.  I've been concerned that it will be hard to find anything if something breaks given the run on AT gear this season.  

Stormy, Stormy Night

What a great night to be a weather weenie.  Heavy mountain snowfall.  Valley thunder and small hail.  It doesn't get much better than that, unless we also got more post-frontal snow. 

Let's start with the northern Wasatch. In the pre-frontal environment last evening, it was absolutely lit, with high radar reflectivities developing over the upstream lowlands and extending downstream over the Wasatch Range.  

During this period, Snowbasin's Boardwalk site recorded 0.86" of water-equivalent snowfall in two hours.  I looked at their snowcam and inferred a 4"/hour snowfall rate.  Total overnight snowfall reported by the resort was 18", with 1.99" of water equivalent at the Boardwalk site.  That's great high-density base builder and just what we need in November.  

Moving to the Salt Lake Valley, the front came through with a strong convective line, lightning, and thunder (apologies for the change in radar color scale, but it's early on a Saturday morning).   

The rumblers woke me up, but a meteorologist never complains about being rousted by weather.  Pea-sized hail pelted our windows and remained on our porch this morning.

If one were to complain about this storm, it left my place with minimal accumulation as things shut-down quickly in the post-frontal environment.  C'est la vie.

Finally, moving to the central Wasatch, the Utah Avalanche Center reports 7-15 inches of snow with 0.8-1.5 inches of water.  Alta-Collins sits at 15" on the interval board and is up 8 inches in total snow depth.  The 0.96" of water recorded by the gauge is probably low due to the strong winds.  

If you're thinking of ski touring today, keep in mind that (a) Alta is now closed to uphill, (b) the UAC rates the hazard as considerable, and (c) its really windy up there.  I just took a look at observations at crest level in the central Wasatch and at one site it has been gusting over 86 mph, with a peak of 99 mph, since 11 PM yesterday.  

We'll see some mountain snowshowers today that will taper off this afternoon.  Accumulations of maybe an inch or two at best, unless a strong squall develops. 

The models have backed off on the system for tomorrow, shunting it mainly to the north.  Maybe some snow showers with light accumulations in the central Wasatch.  An inch or two if we're lucky.  Less is more likely.  

If you like wind slab and don't find enough of it today, wait until Tuesday.  With an approaching trough, the GFS is advertising increasing flow with the dreaded flags on the wind barbs at 700 mb (10,000 ft) penetrating into northern Utah by 0000 UTC 18 November (5 PM Tuesday).  

Those represent free-atmosphere winds of 50 knots or more.  Expect more wind redistribution.  

Base and Blow Ahead

Things are looking pretty exciting for the next few days, with a moisture laden storm for Friday night with strong winds, a decent frontal passage Friday night, post-frontal instability showers Saturday, and then another system Sunday.  Did I mention it's going to be windy?

Let's talk large-scale setup for Friday night first.  At 0000 UTC 14 November (5 PM MST Friday), the GFS forecast shows a strong upper-level trough and low-level cold front approaching Utah.  Moisture is spreading into northern Utah things beginning to get going over the northern Wasatch in the pre-frontal southwesterly flow.  It's a warm storm to start, but I'm hoping we'll see snow levels at the start of the storm late Friday afternoon near or just below the base of Snowbasin (6500 feet).  

The airmass ahead of and with the front is a juicy one.  The GFS integrated vapor transport forecast shows atmospheric river conditions penetrating across California and Nevada into northern Utah.  

Source: CW3E

Such conditions, with strong cross-barrier moisture transport, should persist over the northern Wasatch for about 6 hours as the front approaches. This is a situation ripe for heavy pre-frontal and frontal snowfall at Snowbasin and on Ben Lomond Peak.  I would not be surprised to see water-equivalent precipitation rates of 0.3 inches per hour at the Ben Lomond Peak SNOTEL.  

The GFS has the surface and 700-mb front passing through northern Utah at 0900 UTC 14 November (2 AM Friday).  Note the transition from southwest to northwest flow across the northern half of the state at that time (lower right), and west-southwest to west-northwest at 700 mb (lower left).  

The time-height section below for salt Lake City summarizes the situation,  Tomorrow (red box) we'll see strengthening southerly flow and relatively mild conditions compared to the week so far.  During the afternoon, high clouds will thicken and lower.  

Things get rolling late in the afternoon or in the early evening as strong, moisture-laden southwesterly flow impinges on the Wasatch range (green box).  Snow levels should lower fairly quickly with the onset of precipitation to about 6500 or 6000 feet.  The front passes salt Lake City at around midnight to 2 AM, with heavy precipitation and snow levels falling to the valley floor.  

Post-frontal snow showers will continue in the wake of the front (blue box), especially in the mountains.  Some lake effect could occur late Friday night and Saturday morning.  After a break late Saturday/Saturday evening, we reload for another storm Saturday night and Sunday (purple box). In the interest of time, I'm going to skip discussing that storm.  You'll just have to look it up yourself. 

For the Friday night/Saturday storm, the NAM is gong for 1.19" of water and 13.5" of snow at Alta through 11 AM Saturday.  The GFS calls for .81"/10.5".  For those of you keeping score at home, this is a rare time when the NAM is more excited than the GFS.  The SREF mean for water through 18Z 14 Nov (11 AM Sat) is about .75"/14", with a range of .4" to 1.35"/6" to 22"

I'm pretty encouraged by the storm and would lean toward .6 to 1.25" of water and 8-16" of snow by 11 AM Saturday at Alta Collins.  I expect it to be a windy affair as well.  I'll be hoping that once again I underpromise and the storm overproduces.

The Utah Avalanche Center is not yet issuing avalanche ratings, but I would be on full alert if I was heading out touring this weekend, remembering that the resorts, if they continue to allow uphill skiing, are de facto backcountry.  There are lots of hazards lurking beneath the snow surface.  Our medical community is beyond stressed.  Let's not add to their burden.