Wednesday, January 31, 2024

Southern Track Goldilocks Storm

Snowfall in the central Wasatch has been scant in recent days with a ridge in charge, but that will be changing tomorrow.  

Currently a monster cyclone lurks over the eastern Pacific with clouds along the accompanying cold front pushing into California.  Hooray!

This is, however, a splitting storm so the GFS forecasts the primary 500-mb trough and so called "synoptic forcing" associated with the system (also referred to as large-scale lift as indicated by the red upward vertical velocity contours in the upper left-hand panel below) to be over northern Mexico, SoCal, and Arizona at 1200 UTC 2 Feb (5 AM MST Friday).  

However enough of the frontal remnants and instability move through northern Utah that the GFS does give us periods of snow showers, including Friday night as the remnants of the front have moved downstream and we are in unstable northwesterly flow.  

A look at the GFS-derived guidance for Little Cottonwood shows mild conditions today, but transitioning to cooler by Saturday.  The GFS puts out almost 1.2" of water by Saturday 11 AM MST Saturday, which converts to about 18" of snow.  Given the decline in temperatures and wet-bulb zero levels, snow-to-liquid ratio is expected to increase over time resulting in a right-side-up snowfall.  

That said, it may take a bit to stack up as the 18" of snow the GFS produces in this case falls over a 36 hour period.  

A quick look at the downscaled SREF ensemble shows most members (23/26) producing 10" or more of snow for Alta-Collins through 0000 UTC 4 February (5 PM Saturday), with most of that falling by Saturday morning.  

Although the splitting nature of the storm gives me some heartburn, by and large I think this looks like a decent storm in which we are likely to get 12-20" of right-side up bliss in upper Little Cottonwood by Saturday.  

Monday, January 29, 2024

Statewide Temperatures in 2023

Following up on the prior post looking at record temperatures globally, let's zoom down to the state level.

The first half of 2023 was actually fairly cool statewide.  In fact, the January–June mean temperature for the state was only 41.6F, making it the coldest January–June since 1984. 

Source: NCEI

By midsummer, I was thinking we might be able to finish the year below the 20th century average temperature, which is something that hasn't been done statewide since 1993.  However, the latter half of 2023 was quite warm.  In fact, for July–December the statewide average temperature was 55.3F, which ties for the 3rd highest on record just behind 2020 and 2021.

Source: NCEI
As a result, 1993 remains the last year that Utah's statewide average temperature has been below the 20th century average (note that 2011 tied the 20th century average but was not below).  

Source: NCEI

As can be readily seen from the graph above, we simply do not live in the climate of the 20th century anymore.  That climate is long gone.  The statewide average temperature in the 20th century was 47.6F.  Over the last 20 years, it's been 49.4F or 1.8F.  That works out to an even 1C if you like metric. That may not seem like a lot, but that equates to about a 500 foot increase in the mean snow level during winter storms if all other storm characteristics were held fixed. 


Friday, January 26, 2024

2023 Was Warm

Updating graphs for talks and classes now that the numbers are in and processed from 2023.  This is no surprise given what has been observed throughout the year, but 2023 was the warmest year on record. 

Expect more records in the future.  Every year might not top the previous given that there is some variability from year to year, but the long-term trend is not our friend.

Thursday, January 25, 2024

Tough Week Ahead for Western Powder Skiing

We have a weak storm moving through northern Utah today, after which we will have to hope that the advertised Groundhog Day pattern change comes through.  

Today's storm is associated with a weak 700-mb trough that at 1200 UTC was located along the Utah–Nevada border. 

As I type this at 7:50 AM, it is producing some valley rain here at the University of Utah, but so far not much at upper elevations.  The passage of the trough and then the unstable postfrontal period looks to produce some snow though for the mountains.  The GFS is going in for 0.45" of water and 6.2" of snow for Alta-Collins. 

The HRRR is pretty unenthusiastic producing only 0.17" of water and just under 2" of snow. 

Looking at the local radar, I was quite discouraged as the band ahead of the trough is nearly through with little accumulation in the central Wasatch (the southern Wasatch is doing better), but there are some instability showers behind the trough over Nevada, so maybe we can get something going eventually as that part of the system moves through.  

Source: College of DuPage

This is a tough forecast given the model spread.  The HRRR is nearly a nothing burger.  The GFS might suggest 4-8" for Alta-Collins.  I'm going to lean to the latter and say we'll get something in the 4-8" range eventually as the more unstable part of the storm moves through, but that is counting heavily on the Alta Cloud to do its job.  Let's hope it does because the forecasts until about Groundhog Day are pretty dismal for western powder skiing. 

Looking over the models, they are calling for a high-amplitude ridge to develop over the western US with a series of warm systems moving into the Pacific Northwest and British Columbia.  Dry, inversion weather will predominate over the western interior, with rain at times to high elevations over the Pacific Northwest and southern British Columbia.  As an example, below is the GFS forecast valid 0000 UTC 31 January (5 PM MST Tuesday) showing a deep cyclone off the BC Coast and a potent and warm atmospheric river extending from the sub tropics to the Pacific Northwest/Southwest BC coast.  

The models are hinting at a pattern change around Groundhog Day, so let's hope it comes through.  Note that if that pattern happens, it has nothing to do with weird men in top hats pulling a rodent out of the ground.

Tuesday, January 23, 2024

Steenburgh Winter (Sort of)

This has been a ski season characterized by dramatic boom and bust cycles that are very clear in the snowpack water equivalent trace for Snowbird below.  Evident are two major storm periods from December 1 to 10 and from Jan 3 to 22 that added 6.4 inches and 8.6 inches of water, respectively.  Together, these two periods account for 15 inches of the total water equivalent in the Snowbird snowpack, or about 75% of the 20.1" total.  

Source: NRCS

During the January storm period, it is likely that we eclipsed the 100 inch mark on the Alta-Collins total snow depth stake, but due to some erratic reports, it was difficult to know with confidence if that was the case.  The time series of total snow depth at that site over the past two weeks is below and it shows 100" first being eclipsed late in the evening on January 13.  Shortly after that though, the measurements drop abruptly back down to 94 inches and then bounce around from the high 90s to 118 inches until the 16th when things settle down again.  We have remained at or above 100" since then.  

Source: MesoWest/Alta Ski Area

January 13 was quite windy.  The Mt. Baldy anemometer hit 90 mph overnight on the 12th and ultimately succumbed to riming on the 14th.  Thus, a combination of wind transport and instrument flakiness greatly complicated matters. 

Given how late in the day we first reached 100" on the 13th, and the fact that the non 118 inch reports next reached 100 inches late in the day on the 14th, I'm going to declare 14 January as the official start of Steenburgh winter, that period between the first day of 100" on the Alta-Collins Snow Stake and February 10th when the sun angle begins to have an increasingly caustic effect on the snow.  This period is the crème de la crème of backcountry skiing given the deep snowpack and low angle sun, enabling powder to persist for long periods on a wide range of aspects.  

However, this year we have been thrown a curve ball and it is one of the reasons why I am not celebrating.  That curve-ball was the prolonged dry period from December 10 to January 3, which ultimately led to the development of a persistent weak layer that is now buried by all of the snow that fell over the past couple of weeks.  This led the Utah Avalanche Center to raise the black flag for extreme avalanche danger at all elevations and aspects on Sunday January 14. 

Source: Utah Avalanche Center, issued 14 December 2024

About 30 years ago, when I was leaving Seattle for Salt Lake City, famed avalanche forecaster Sue Ferguson, a former director of the Utah and Northwest Avalanche Centers, told me that in Utah you can avoid many avalanches by simply waiting three days after a storm before entering into avalanche terrain.  This was not meant to be rigorously followed advice as Sue knew as well as anyone that there is variance around the mean, but it was her way of saying that persistent weak layers are less common here and that patience is a virtue in Utah where we are often dealing with new snow and wind-driven instabilities that can heal quickly.  

However, there are years when that is clearly not the case and this is one of them.  That persistent weak layer may have strengthened some in some areas, but we are still dealing with a Russian Roulette snowpack.  We still have considerable avalanche danger on a good portion of the avalanche rose and, as summarized by Drew Hardesty in today's report "dangerous and tricky avalanche conditions exist."  

Drew comments further that cautious route finding and conservative decision making are essential.  Indeed, many people that I know are laying low right now, staying away from of steep terrain.  

So, Steenburgh winter is here, but the green light is not on in the backcountry.  That said, the coverage is good in the aspens and reports are that the resort skiing has been quite good (I was in Steamboat last week and the snow conditions there were also quite good).  It is always good to reach 100" of snow depth and 20" of water at the Snowbird SNOTEL in January.  In the case of the latter, the median snowpack doesn't reach 20" until February 1st.  

Saturday, January 20, 2024


I spent the last week in Steamboat attending a meeting known as the Weather Summit and helping out a bit at Storm Peak Lab, a major meteorological observing facility at the top of the ski resort that is now operated by the University of Utah after it was transferred over from the Desert Research Institute. 

We arrived late Tuesday, which turned out to be the only day we saw the sun.  

The meeting was structured to allow for morning turns, which featured dust on crust Wednesday morning and cream on crust Thursday morning.  On Wednesday morning, as the airmass warmed, there was a transition in snow crystals from lightly rimed dendrites to rimed crystals. Steamboat has trademarked the phrase Champagne Powder (don't tell the French about this) and the morning snow was of such quality (although not deep).  By mid morning though, the dendrites were heavily rimed, as illustrated by the snow crystals on my shell.

A lot of work has been done using data from Storm Peak Lab to examine cloud characteristics and snow growth processes.  A favorite paper of mine is Hindman et al. (1994) which examined the concentration and size of cloud droplets over a multiyear period at the lab.  Out of 274 samples, 241 (88%) exhibited what we would expect in clouds with "continental" characteristics where as 33 (12%) featured clouds with "maritime" characteristics.  

Source: Hindman et al. (1994)

Over the continents, there tends to be a lot more very small particles in the air that are referred to by scientists as aerosols. Some of these aerosols can serve as cloud condensation nuclei, or CCN.  These become the "birthplace" of cloud droplets.  Because there are a lot more CCN, continental clouds tend to feature more cloud droplets per volume of air.  These droplets also tend to be smaller.  In contrast, in maritime clouds, there are fewer CCN, there tend to be fewer cloud droplets, and they tend to be larger.  All else being equal, those larger droplets more efficiently rime falling snowflakes, leading to heavily rimed snow crystals (such as those pictured above) or graupel.  

There are other pathways to creating rimed crystals or graupel in clouds even in continental clouds, but clouds with maritime characteristics do it more efficiently.  I didn't take a look at the aerosol concentrations on Wednesday, but on Friday they were low, so perhaps this was a contributing factor to the development of rimed crystals on Wednesday.  

Sunday, January 14, 2024

Had Enough Yet?

I'm up early and looking at the overnight numbers.  It was quite windy last night, so there is more uncertainty in the automated observations than usual, but from 5 PM yesterday to 5 AM this morning, the Collins gauge measured 1.91" (48 mm) of water and probably about 20 inches of snow (the 33 below is spurious).  The drop in total snow depth is odd, and that is one reason why I mention the uncertainty.  

Assuming it came in around 48 mm in 12 hours, that's somewhat unusual.  Below is a histogram of twice-daily 12-h snowfall and water equivalent (called liquid precipitation equivalent in the chart) over a 22 year period at Alta.  48 mm or more happened 10 times in that period, so about once every 2 years.  

Source: Wasserstein and Steenburgh (2024)

Since those are twice daily measurements, we would probably expect a few more events than that for any 12-hour period, but still, it appears we were in unusual territory.  Combined with wind and a weak snowpack, I suspect things were pushed over the edge last night.  Closing both canyons and declaring interlodge were 100% the right call, although you don't need a meteorologist to tell you that.  

Give the highway maintenance, public safety, and snow safety teams all your patience and respect today.  We are deep into too much of a good thing territory.  I love snow, but better it be spread out more than come like this.  

Saturday, January 13, 2024

Storm Cycle Update

Snow continues to stack up in the Wasatch and the red flag continues to fly for the backcountry avalanche danger.

Utah Avalanche Center Forecast Summary Issued 13 January 2024

From 5 AM MST Wednesday to 5 AM MST Saturday, the Alta-Collins automated snow-depth sensor has ticked off 30" of snow, putting us half way to the over-under that I set at that time for the remainder of the storm cycle through Monday (see Shall We Set the Over Under for This Storm Cycle?).  It also lifts us up to about 43" since Jan 9 and 68.5" since Jan 4.  These numbers are based on a mixture of data from the Alta Snowfall history and the automated snow stake so they may differ slightly from other estimates, especially given yesterday's wind.  I notice that the Alta web page is listing the storm total as 44", so they must be using Jan 9 as the start date. 

As I write this at 7:20 AM, we are in a bit of a lull, but I say that with a caveat. There are still some snow showers around, including three wind-parallel bands that extend downstream from the three primary ridges in the central Wasatch and into the Wasatch Back.  It is not unusual for the radar to exhibit echoes over those ridges due to ground clutter, but these bands clearly extend well downstream.  The one that extends downstream from the Mt. Raymond – Park City Ridgeline was best developed when I grabbed the image below and extended downstream to near Jordanelle Reservoir.  

Expect some periods of snow today, increasing in frequency and intensity later this afternoon as the next major system approaches.  The GFS forecast valid 0300 UTC 14 January (8 PM MST Saturday) shows  a compact upper-level trough over southern Oregon with strong integrated vapor transport, warm advection, and precipitation over or just upstream of northern Utah.  

This is a recipe for a transition to higher-density snow and potentially higher water-equivalent snowfall rates, especially as the trough approaches overnight, as illustrated below.

Tomorrow, with the trough through, we transition to northwesterly flow with, you guessed it, more snow.  

As noted above, the backcountry avalanche danger is high, with forecasts calling for it to rise to extreme.  In the video below, Trent Meisenheimer calls the avalanche danger "as wild as I've seen it in my tenure." 

My touring party yesterday elected to go for a "trail" tour for exercise, staying entirely in thick trees, and I think we have all decided to give up on mid- and upper-elevation ski touring and let Mother Nature have "fun" for a few days.  I often talk about outlier mode in meteorology, but these are outlier mode conditions for the snowpack and microterrain features in many "safe" zones are producing hair trigger avalanches that are catching experienced riders.  One skier was buried yesterday and fortunately recovered by their partners.  The provided a very honest and sobering write up that is available at  I am grateful all is well and thankful they had the courage to share this report.

Getting back to the forecast, I'll focus here on the the latest HRRR run for Alta/Little Cottonwood, which just arrived. Precipitation rates are forecast to be fairly low until about 2 PM, when they start to pick up.  Overnight, you know what hits the fan.  From 11 PM Saturday to 8 AM Sunday the HRRR puts out 1.4" of water and 15" of snow. For the period beginning 5 AM this morning and ending 5 PM Sunday, totals are 2.63" of water and 28" of snow.  This is higher density stuff than we've seen, with our algorithm going for snow-to-liquid ratios below 10:1 prior to the trough passage tonight and the wet-bulb zero level reaching almost 7000 feet.  This might push snow levels to just above the benches.   

The numbers from the GFS (not shown) are a bit lower for that overnight period (0.85" water/10" of snow) and the period from 5 AM this morning through 5 PM Sunday (1.7" water/21" snow).  The GFS is a bit cooler, with the wet-bulb zero level only reaching 6000 ft.  Nevertheless, it goes for the higher density snow tonight as well.  

I'll add that the GFS extends farther into the future than the HRRR and it continues to produce snow through 11 PM Monday with another storm on Wednesday.  The Euro is also on board with the Wednesday storm.  

I'm buckled up already, so I'm not sure what to recommend at this point except let the road maintenance, public safety, and snow safety teams have all your patience and respect.  We are deeply in outlier territory.  

Wednesday, January 10, 2024

Shall We Set the Over Under for This Storm Cycle?

I thought for today we could talk about how much snow we might get from this storm cycle.

A storm cycle is a series of storms that occur in succession.  One has to decide when to start or end such a cycle.  There are two options for this one.  One is to start on January 4th, which is when we first started seeing snow after the holiday drought.  The other is to start yesterday, January 9, as there was nearly a 24-hour break in the snow.  

I'll use both here.

Jan 4 start: 38.5" so far (per Alta Snowfall History)
Jan 9 start: 13" so far (per Collins automated measurements)

These are a little inconsistent because the Collins automated measurements don't perfectly correspond to the snowfall history, but this is only for fun and we're not running a professional gambling house here, so I'll go with it.  

How much will we add to these totals?  For the purposes of defining and end, I'm going to use 1200 UTC 15 January (5 AM MST Monday) as most models suggest there may be a break then.

Let's start with the GFS.  After deducting what it produced overnight last night, the GFS is producing an additional 4.85" of water and 67.8" of snow for Alta through 5 AM MST Monday.  

We don't have a comparable product for the Euro, but it is coming in with about 3.2" of water which if we use the mean snow-to-liquid ratio from the GFS converts to about 45" of snow.  The Euro does tend to be the drier of the two models for Alta.

Finally, we have the downscaled NAEFS.  I've never seen numbers like these being output from this product.  Across the whole western US, the mean bias of the water equivalent forecasts produced by this technique is close to zero, but my impression is that it is typically high for Alta (but I haven't confirmed this).  Additionally, this uses an old and very simplistic algorithm for snow-to-liquid ratio, and in a situation like this with strong winds and high water equivalents, it is probably overestimating the snow-to-liquid ratio during some parts of the storm. That said, after deducting about 1" of water equivalent at 15" of snow it called for overnight, the NAEFS mean calls for another 7" of water and 100+ inches of snow.  

After looking over the models for the period, I consider the real crux for these forecasts to be the period from tonight, when we will be in the unstable postfrontal flow, and then Friday when we transition to a more stable northwesterly flow with high integrated vapor transport.  The GFS forecast for the latter is depicted below.  

These are environments where I see a wider range of possible outcomes, unlike today, especially this afternoon, when it looks like it is a lock to get the goods with the frontal approach and passage.  Then there's the big storm system for the weekend, which is associated with an intense and compact upper-level trough and inland penetrating atmospheric river.  

These are amongst the most exciting forecasts I've seen in my time at Utah.  We have had big storm cycles, but the number of models calling for big accumulations in the mountains and periods of disruptive snowfall in the valleys is remarkable.  

So how high does one go for the rest of the storm cycle?  For an over under, I'm going to go a bit below the GFS total and add another 60" to what we have already.  That puts us at

Jan 4 start: 38.5"+60" = 98.5" 
Jan 9 start: 13"+ 60" = 73"

Another way to think about the over under is that it represents the middle point of all of the possibilities.  There's a 50% chance of less and a 50% chance of more.  

The National Weather Service would have access to an objectively determined "over under" from their National Blend of Models. Perhaps someone from there can share it in the comments below.  For what it is worth, what the call the "deterministic" forecast from this product is calling for a bit over 80".

NBM forecast for Alta screenshot at 10:16 AM MST 10 January 2024

I confess that my 60" above could reflect my conservative nature.  I have a hard time going way out on the limb for the most extreme storms.  

In the end, we will get what we get and we won't throw a fit.  We are going get it today and over the weekend and possibly quite a bit in between. It is going to add up to a lot of snow, big traffic snarls, dangerous avalanche conditions, terrain closures, etc. etc. etc.  

Are you over or under?

Monday, January 8, 2024

Mother Nature Is About to Release the Hounds

Today is probably going to be the quietist of this work week.  For the most part, it is dry, although if you peer to the west from the University of Utah, you can still see some of our dendritic friends are still falling over the Oquirrhs.  

Cams from the central Wasatch also show some flakes falling, although it's not adding up to much.  

Source: Alta Ski Area

This is what constitutes a break in our current storm cycle.  It will persist through tomorrow morning, and then Mother Nature will release the hounds.  It doesn't matter what elevation you live at in northern Utah, you are going to be experiencing significant snows through the weekend.  

Let's get to it.  First, the GFS forecast calls for a frontal system to be moving across northern Utah by 0000 UTC 10 January (5 PM Tuesday.  

It is likely that this will bring all-elevation snow to northern Utah for the evening rush hour and significant snows overnight for the mountains and the Salt Lake Valley.  As such, the National Weather Service has issued a Winter Storm Watch for much of the Wasatch Front and the mountain valleys.

Tomorrow will be a good day to monitor forecasts and consider an early departure from work if appropriate.  This is a storm that will likely affect the northern Wasatch Front earlier and eventually the southern Wasatch Front.  

That's all fine and dandy, but how about we do it again on Wednesday?  Sure thing.  The GFS brings another frontal system in by 0000 UTC 11 January (5 PM Wednesday).  

Then, for the skiers, how about some unstable northwesterly flow on Thursday.

In general, there is good agreement between the GFS and the ECMWF models through Thursday.  Thus, I'll be bold and share the GFS-derived time series for Alta.  Now don't look ahead.  Do not peak beyond 5 PM Thursday. I repeat.  Do not peak beyond 5 PM Thursday.  Through 5 PM Thursday the GFS is putting out 1.58" of water and 23.4" of mostly low-density snow.  The system tomorrow afternoon may produce some higher density snow to start, afterwhich snow to liquid ratios flctuate between 13:1 and 20:1.  

By and large, this period looks locked and loaded for 20–30 inches at Alta from tomorrow afternoon through 5 PM Thursday, although I confess that I want to say "possibly more."  Much will depend on what occurs during the post-frontal period on Wednesday night and Thursday.  

Now you can look beyond 5 PM Thursday.  Holy cow!  If you want to push the backcountry snowpack to the breaking point, the GFS forecast for the weekend might do it.  At 0000 UTC 14 January (5 PM Saturday) it puts a beast of an upper-level trough and frontal system over the Pacific Northwest.  Utah is at the tip of an atmospheric river with strong, moist, crest-level flow.  

Eventually that trough and it's cold front come through by 1200 UTC 14 January (5 AM Sunday).  It's a monster system, with screaming winds, abundant moisture, and a hell of a punch.  

Little wonder that the GFS is putting out more than 4" of water and 60 inches of snow for Alta-Collins through Monday per the time series above.

That is, however, a fairly extended forecast, so let's look at a few other models.  One is the ECMWF. For 1200 UTC 14 January (5 AM Sunday), it actually has a somewhat similar forecast, but the trough is a tad slower and less intense.  We would still see significant snow, but the crest-level winds might not be as strong.  

Looking at the downscaled NAEFS, nearly all of the members are pretty jacked for the period through 15 January.  The mean water equivalent for Alta is 5 inches and the lowest amount is just over 2.5 inches.  

The bottom line is that Mother Nature is going to release the hounds.  This looks like an incredibly active storm period.  It is essential to monitor forecasts (details do change), not just for the mountains but also the valleys, and avalanche forecasts.  Be respectful of resort and backcountry closures and give our friends in the snow-safety community your support.  The weak snowpack that currently exists is going to get a serious stressing.  

Sunday, January 7, 2024


All caps seem appropriate given the overnight snowfall and the forecasts for the coming week, which can be summarized in two beautiful words: Cold and Snowy.  

Based on the Alta-Collins automated observations, Alta has picked up 21" since the holiday snow drought ended on Thursday through 10 AM this morning.  This is all of the low-density variety with a water content of about 6%.  I might have preferred some higher density snow to start and help bury the old snow surfaces, but beggars can't be choosers given the lack of snow through the holiday period.  

Additionally, the forecasts are spectacular.  More snow showers today, then a bit of a break before the next system drops in late Tuesday.  The GFS forecast valid 0600 UTC 10 January (11 PM MST Tuesday) shows a large-scale pattern with an upper-level risge well off the west coast and strong northwesterly flow moving over the northeast Pacific and into the interior western United States.  

Given the strength of the flow and the various "wiggles" in the jet stream, nailing down the timing and intensity of snowfall may be difficult, but a look at out downscaled NAEFS forecast shows that after today's snow and then the dry period through about 0000 UTC 10 January (5 PM MST Tuesday), we're going to see a series of systems coming through to add to totals.  

There is actually an unusually tight clustering in those forecasts (we typically see a greater range for Alta).  I don't think that reflects that all these forecasts agreeing on the details, but they do agree on this being an active period.  From 0000 UTC 10 January (5 PM MST Tuesday) through 0000 UTC 14 January (5 PM MST Saturday), water equivalents are generally in the 2-5" range and snowfall amounts are quite high.  I'm not going to say the numbers because this particular product tends to be a bit jacked and doesn't include the influence of wind and compaction on snow-to-liquid ratio, but it looks like a major storm cycle.  

By next weekend, we will be looking at a new mountain range with low-elevation snow and better coverage at upper elevations. 

I'm working today, but am heading out soon to buy some new gloves as my old ones are shot and professional grade insulation will be needed for this period.  

Thursday, January 4, 2024

Change You Can Believe In

The stoke is high here at the Government Weather Control Office as we have finally been allowed to pull the "winter" lever for Utah and we are starting to see results.  

First, we got a skiff of snow overnight at the University of Utah.  Very exciting!

This snow is being produced by a closed low that is tracking to our south and is expected to be over western New Mexico by 1800 UTC (11 AM) this afternoon.  

Normally I would just say today is no game changer but any snow right now seems like a game changer.  For Alta, the HRRR generates little to no snow with this system today, but the GFS produces about 4" of low density fluff.  I'll go for 1–3" for Alta by 5 PM. Be grateful if we get that.  

But there's more coming.  Another weak upper-level trough moves into Utah tomorrow. Although it is weak, there's enough moisture and orographics in northwesterly flow that we continue to see periods of snow in the mountains tomorrow.

That snow tapers off tomorrow night.  

The HRRR, which is bearish on today and generates squat at Alta, is more enthused for tomorrow and generates about 6" of low-density snow before shutting things down by 8 PM.  

The GFS runs later than the HRRR, so the plot below only goes to 11 PM Friday, but it shows the GFS dripping out light snow through that time that ultimately adds up to 14" (including today). The snow to liquid ratios in the GFS are quite a bit higher than in the HRRR, so this reflects both the GFS being wetter, but also producing lower density snow.   

I'm inclined to go with an additional 5-10" of low density snow through 11 PM Friday on top of the 1-3" from today.  That's great, and it will help a lot, but expect a lot of bottom feeding through at least tomorrow morning.  Maybe by afternoon, if we come in on the high side of expectations, things will begin to feel smoother in areas that aren't heavily moguled.  

Beyond that, I currently like what I'm seeing in the models.  First, it looks to be cold.  Second, there are enough troughs coming through that we will probably get something additional next week.  The first opportunity is Saturday night through Monday as a trough digs into the US Southwest. 

This one might not be a direct hit for northern Utah, but we should get something.  Then the models are advertising the potential for another storm the middle of next week.

For Alta, the NAEFS is gnerating anywhere from about 1.25 to 5 inches of water through 0000 UTC 11 Jan with substantial snowfall amounts.  

I'm inclined to dismiss the higher amounts given the tendency of this downscaled product to be a bit excited, but expect improving conditions and increasing avalanche hazard in the coming week.  Monitor forecasts for timing and amounts as the details of trough movement and location still exhibit a range of possibilities.