Exceeding Expectations

Yesterday's storm was great, exceeding expectations in the valleys and mountains.  It has been a while since we've had a storm that came together to maximize precipitation generation, but yesterday's did.  The radar filled in nicely as the trough approached, precipitation continued pretty much without abating throughout the event, and the post-trough, northwesterly flow was quite productive.  It was also a big event in the valley as well as the mountains.  Here are some numbers (lowlands courtesy NWS):

Wasatch Front Lowlands

Fruit Heights through 8 PM Thu: 1.42"

Bountiful Bench through 8 PM Thu: 1.27:

Holladay through 8 PM Thu: 1.21"

Alpine through 5 PM Thu: 0.90"

Wasatch Mountains

Ben Lomond Peak: 1.2" SWE

Snowbasin-Middle Bowl: 1.07" SWE

Alta Collins: 1.36" SWE/13" Snow

Aspen Grove (Mt. Timpanogos): 0.88"

Sundance-Mid Mountain: 0.86" SWE

I've emphasized the higher lowland totals above, but an interesting aspect of the event is that there was very little contrast in precipitation amount between from the Wasatch Front lowlands to the mountains.  Nevertheless, the mountain snowfall brought Alta-Collins up to the magical 100 inch total snow depth.  Hooray!

Source: MesoWest

Our next storm is currently over California, with the parent low further west and associated with a beautiful spiral cloud band.  No need to deface such a beautiful storm by adding an analysis.

This is an unusually deep cyclone for this latitude at this time of year with a central pressure at 1200 UTC of 976 mb.  The analysis below from the Ocean Prediction Center shows significant wave heights of 30 feet just south the low center.  The narrow jet of strong winds that generates those waves is called a sting jet, and Norwegian meteorologists call this very dangerous region for marine vessels the poisonous tail of the bent-back occlusion as it is located where the occluded front wraps around the low center like a scorpion's tail.

Although the poisonous tail won't be stinging Utah, will will get some strong mountain winds as southwesterly flow reaching 55 knots at 700 mb extends across the central Wasatch late tonight.

For tonight through 5 PM Saturday, the NAM goes for 1.42" of SWE and 14" of snow in the upper Cottonwoods, in increase over yesterday.  In contrast, the GFS is now less productive, going for 0.64" of SWE with 5" of snow.  Such, model variability is not uncommon in this business and reflects some of the forecast uncertainty.  As you might infer from those numbers, much of this event will be of the high density variety, due to both high temperatures and high winds, with water contents of 10–12% likely.  Given the high density of the snow, I think I'll go for another 8–14" at Alta-Collins by 5 PM Saturday, which would bring the storm-cycle total to 21–27".

Spring Storm Sampler

I love satellite images like the one above for 1700 UTC (1000 MST) this morning with an overlay of the 500-mb heights (black) and absolute vorticity (colors).  These are two fields commonly used by meteorologists to track upper-level troughs, which I've identified with some pretty ugly red lines.  I also highlighted my best guess for the position of the developing low center with a red "L."

You can see quite nicely the two systems that will impact Utah through the weekend.  The first is currently centered over Nevada and precipitation associated with that system is moving into northern Utah this morning.  At 10 am it was 35ºF at Snowbasin Middlebowl and 33ºF at the base of Snowbird.  Yup, another day for a good shell.  Freezing and snow levels will drop as the system moves in and precipitation picks up, but will be near 7000 feet this afternoon.

The models currently call for a decent break between systems late tonight and tomorrow, with the second moving in late Friday and giving us precipitation through Saturday morning.  NAM forecasts are not quite as wet and snowy as yesterday and generate about 1.7 inches of water and 17 inches of snow in the upper Cottonwoods through 5 PM Saturday (see lower two panels below).

Source: http://weather.utah.edu

An interesting aspect of the model forecasts for these two storms is that the GFS is actually a bit wetter than the NAM, producing 1.8 inches of water by 5PM Saturday, which is pretty unusual.  Most of that difference is produced by the 2nd storm.  The GFS is a lower resolution model, which means it doesn't resolve the terrain of the western U.S. as well.  I think what may be happening in this case is that the GFS brings too much moisture across the high Sierra with that 2nd storm and this helps compensate for the model not resolving the Wasatch all that well.  Thus, this may be a case of two wrongs make a right.

I'm guessing the several inches we get today might ski decent tomorrow up high in the backcountry as it should be right side up even if it is a bit dense to start.  Through Saturday afternoon, I'll go for 15-24 inches total in the upper Cottonwoods with about 2 inches of water.  No shoveling in the valleys.

Sunsets and Storms

Much to talk about today.  First, have you seen the sunsets the past couple of days?  Unbelievable.  The photo below, taken Monday doesn't do them justice, but does capture a nice sun pillar if you look close.

The presence of altostratus clouds (upper right of photo above) and lenticular (mountain wave) clouds has certainly helped paint the scene, but I'm wondering if we might have some aerosols, possibly Asian dust or pollution, moving over us in the upper atmosphere to give us a bit more orange tint than usual.  Perhaps someone can dig in and have a look as I have other important things to keep me busy today.

Storms

After a sunny day today, things are looking pretty active for Thursday through Saturday and possibly Sunday as two major troughs embedded in the southwesterly to westerly large-scale flow rumble through the state.  There is a lot going on, so I'll summarize quickly with two graphics from the 1200 UTC NAM.  The first is the total precipitation (snow water equivalent) produced by the NAM through Saturday afternoon showing more than 5 inches over portions of southern California, more than 1.5 inches in portions of southwest Utah, and up to 2 inches in the northern mountains of Utah.

Source: NCEP

Timing and intensity will vary geographically and there's still some uncertainty with regards to the specifics.  For Alta and the upper Cottonwoods the 1200 UTC NAM generates precipitation in two pulses on Thursday and Thursday evening, and then again late Friday and Saturday, yielding a total through 5 PM Saturday of nearly 2.5 inches of water.  Being that these are generally warm storms (there are some fluctuations in temperature as each goes through), our snow algorithm is converting that to about 25 inches of snow with a mean water content of about 10%.

Source: http://weather.utah.edu

The first storm might be a bigger producer in the northern Wasatch and Timpanogos area given the prevailing southwesterly flow.  Uncertainty in the track of the second storm, and it's interactions with another system digging into the Pacific Northwest is such that I'm not going to speculate on the details of that event.  Through Saturday, the events look to be rain producers in the valley, with snow tickling the benches at times.

Atmospheric Rivers

Both storms contain atmospheric rivers, filaments of strong moisture flux with a subtropical tap.  In contrast to the previous atmospheric river events we've seen the past few weeks, the atmospheric rivers in these events interact with the high Sierra.  During the first event, for example, low-level flow deflection upstream of the Sierra combined with the depletion of water vapor by heavy precipitation over the Sierra and upstream ranges of southern California, means that the strong atmospheric river conditions do not penetrate directly into northern Utah.  You can see this to some degree in the image below.

Source: NWS

No worries, the remnants in this case should suffice.  Note, however, that as the atmospheric river slides southeastward, it eventually moves past the high Sierra and a nice filament of moisture is able to penetrate with less topographic modification into southwest Utah.

Whatever the northern Wasatch get out of this storm, it would have been more if it wasn't for the high Sierra.

Explosive Cyclogenesis

The formation of a cyclone, a large-scale area of low pressure, is known as cyclogenesis.  Explosive cyclogenesis is the rapid formation of a cyclone, generally defined as having a deepening rate of either 24 mb in 24 hours or 18 mb in 12 hours at 60ºN latitude.  Because it is more difficult for a cyclone to deepen at lower latitudes, equivalent deepening rates at 35ºN are 16 mb in 24 hours and 10 mb in 12 hours.

The second in this series of storms produces an explosively deepening cyclone off the coast of California that is forecast by the NAM to have a central pressure of about 975 mb at 0300 UTC Friday (2000 MST Thursday).

Source: http://weather.utah.edu

In the NAM, the cyclone deepens about 18 mb in 12 hours, which is fairly impressive for this part of the world.  It won't be a good time to be sailing from California to Hawaii, and, although the storm weakens some, I suspect it will produce some strong winds on the coast as it makes landfall.

Welcome to April

Blue skies, mountain wave clouds, and heavenly spring weather at the U @ 2:30 PM 25 Feb 2014

At 7000 feet and below, everything sure looks and feels like April right now.  There's no snow in the valley, Mountain Dell is closed for cross country skiing, and snow is barely apparent along SR-224 near Kimball Junction.

Source: UDOT/NWS

At an elevation of 6000 ft, the Ben Lomond Trail SNOTEL is the only one in the Wasatch that I am aware of that is below an elevation of 7000 feet.  This is a snowy location with a fairly significant snowpack compared to the Park City area (as usual), but even there, the snowpack SWE is pretty much what one would expect in mid April.  There's even some evidence of a modest decline, although that could also be spurious.

Source: NRCS

Finally, we have the temperatures.  At 2:05 PM, the temperature at the Salt Lake airport is 63ºF, which equates to the average high on April 21st.  The only thing that isn't April like is the snowpack at upper elevations.  Snowpack SWE at Snowbird is consistent with the median for Feb 1 or early June, depending on if you want to argue we have an early or late season snowpack.

Source: NRCS

Setback for Sustainability at the U

The Daily Utah Chronicle, January 28, 2014

The University of Utah administration talks a pretty good game when it comes to sustainability.  Several years ago they formed an Office of Sustainability, now the Sustainability Resource Center, to institutionalize campus-related sustainability initiatives.  There is a President's Sustainability Advisory Board to "recommend policies that propel (my emphasis) the campus toward greater sustainability to the University President."  We even have a new Chief Sustainability Officer.

The U also has the following Sustainability Principles:

• Integrate sustainability into education
• Track and reduce greenhouse gas emissions
• Make the campus a "living laboratory" with experimentation and applied research
• Invest in initiatives that reduce dependence on fossil fuels
• Capture and reinvest net savings into additional projects
• Minimize waste through reuse, recycling, and reduction, as well as composting
• Purchase sustainable products, services, and food
• Encourage mass and alternative transportation, including walking and biking
• Use no more water annually then what falls within campus borders

Finally, if you walk around campus and talk with faculty, staff, and students, everyone is concerned about the wintertime air quality.  In fact, I know of at least one faculty member who is moving to another University because of it, and I suspect there are others.

Nevertheless, the U is moving forward on plans to build not one but two parking structures on campus beginning this spring.  The first is the Business Loop Parking Terrace with 800 covered parking stalls, which will be located just west of the Huntsman Center.  The second is the Northwest Parking Terrace with 350 stalls, which will go between the Naval Science and Sutton Buildings near 100 South.  I haven't seen the final quote of the costs of the structures, but the $6.3 mil reported in the Salt Lake Tribune in April 2013 for the Northwest Parking Terrace equates to $18,000 per space.

As Einstein said, insanity is doing the same thing over and over again and expecting different results.  The building of these parking structures is an investment in the status quo and goes against several of the sustainability principles outlined above.  It suggests that the U is willing to pluck the low-hanging fruit, but is unwilling to do what is really necessary for sustainability.  One look at the U Facilities Management web site shows a serious disconnect between words and actions (boxes and question mark annotated).

To be sure, I'm not opposed to parking on campus.  I am a mixed-mode commuter who uses a range of approaches to get to campus, including driving perhaps two days a week when averaged over the year.  I don't think, however, that the U is doing all it can to maximize the parking that we do have on campus.  Let's compare the options at the U to those at the University of Washington.

The U essentially has "all or nothing" parking permits.  Although you can pay extra for a reserved space or a garage permit, most commonly faculty purchase an "A" Permit, which costs $348/year (~$1.50/day assuming ~230 working days) and allows for parking in the A, U, and E spaces.  Students can get similar permits to park in the U or E spaces.  Although all U faculty, staff, and students get a free pass to ride transit, once someone has purchased a parking pass, there is no financial incentive other than the cost of gas to encourage people to take transit.

How about the University of Washington?  For starters, they charge more for parking, but they also provide a much wider range of options.

Source: http://www.washington.edu/facilities/transportation/commuterservices/parking/faculty-staff-student

In particular, they have individual commuter tickets, discounted parking passes for employes who drive to campus twice a week or less, and discounts for night, swing, carpool, and impromptu carpool.

Some of these options might not make sense at the U where parking is cheaper (but that won't be the case for long as we are clearly on an unsustainable path with regards to campus development and parking), others could be implemented to provide financial incentives for the use of mixed mode transit (e.g., individual commuter tickets) and parking at lower-demand times (e.g., swing).  The idea is to provide a mix of options that help to minimize single occupant vehicle trips while maximizing use of the existing parking and transit infrastructure.  

Let's look specifically at the individual commuter ticket.  With an ICT, you purchase a book of 26 ICTs and simply mark one and put it on your dash when you want to park.  They don't have an expiration date, so if you use alternate transportation a lot, you can greatly reduce your parking costs.  When you buy an ICT, you are issued a next purchase date, which is based on an average of 2-days of week of parking.  You can't buy another ICT book until that date.

The ICT was very popular when I was at the University of Washington in the 1990s.  I think a key aspect of the system is that it recognizes that mass transit isn't right for everyone all the time, so it provides flexibility.  Let's hope the U will start to think out of the box and do a bit more than pave and park.  

Spring Fever!

Spring has sprung in the Salt Lake Valley where we are being treated with an incredibly spectacular bluebird day.  The high temperature at the Salt Lake City airport may eclipse 60.  I wasn't in the mountains today, but suspect the skier grins are a mile wide, although the sun and high temperatures may be spoiling the snow a bit on some aspects.  Unlike spring, when the snowpack is sometimes dirty and dusty, it is currently bright white, providing spectacular contrast with the blue skies.

With the warm weather, high snow levels, and valley rain we have had the past couple of weeks, I feel like this cool season we've had two falls and a spring rather than a fall, winter, and spring.  Yeah, it was cold, snowy, and polluted in the valley in December and January, but the mountain snowpack was fall-like until only recently.

Mild weather looks to continue through the coming work week, with a warm storm late in the week.  If everyone gets their bikes out, maybe Mother Nature will bring back winter.

Ooops

You can find the advertisement above in the University of Utah campus bookstore.  It has clearly been composed to appeal to Utah skiers and snowboarders, including the use of the phrase "The Best Snow on Earth", which is cleverly changed from The Greatest Snow on Earth, which is trademarked by the State of Utah.  There is, however, something fundamentally wrong with this ad, at least as far as Utah is concerned.  Can you spot it?

Close, But Not Close Enough

Once again, the storm track is tantalizingly close, but not close enough to bring anything in the way of a major storm to the Wasatch over the next 4–5 days.

The pattern this morning is characterized by a high-amplitude ridge over the Gulf of Alaska, with toughing over the upper midwest of the U.S.  This results in strong northwesterly flow at upper levels from Washington into Colorado.

Such a pattern frequently results in strong downslope winds to Colorado's Front Range, and wind gusts last night at the National Center for Atmospheric Research's Mesa Lab reached 90 miles per hour.

Source: NCAR

This particular pattern is fairly stable and expected to persist over the next few days.  A number of disturbances rippling through the flow will bring mountain snows to the Pacific Northwest, Wyoming, and lesser amounts to portions of northern Colorado, but as things look now, we're largely shut out.

Source: NCEP

We've seen this movie already a few times this year and it is one of the reasons why Steamboat is reporting a larger seasonal snowfall than Alta (279" vs 262.5").  The storm track is setup just right for systems to slide to our north while they dig into Colorado.  Although the next couple of days probably won't bring a major dump to Steamboat, they will something while we get nothing.

The End Is Near

Source: http://www.keepcalm-o-matic.co.uk

After a 2nd winter of hideous air quality, we are now approaching the end of the inversion season.  

As shown in the graph below, days with PM2.5 concentrations > 17.5 (blue) and > 35 ug/m3 (red) are most common during the heart of the winter and drop off dramatically after the 7th week of the year (Feb 12-19).  

Source: Dave Whiteman, University of Utah

Thus we are almost out of the woods.  There are, however, some PM2.5 > 35 days all the way to the 8th week of the year (Feb 26-Mar 4) and an elevated frequency of PM2.5 > 17.5 through the 10th week of the year (March 5-12) (events after that are probably due to blowing dust).  For that reason, I won't stick a fork in it just yet.  

Nevertheless, poor air quality events later in the cool season (e.g., late Feb and early March) typically require a good snowstorm followed by a long-lived ridge.  We do have a ridge forecast to build in for early next week, and we might see an increase in PM2.5 concentrations for a couple of days, but it looks to be a short-lived event without snow cover, so I'm not expecting it to be anywhere near as nasty as what we saw in December and January.  

A Lagging Frontal Snowband

We often think about precipitation being collocated with a surface cold front, but this is not always the case.  Indeed this morning we had some scattered rain and snow showers providing some appetizers ahead of the front, but the main course, a well developed frontal snowband, has developed nicely over the Salt Lake Valley and southern Great Salt Lake over the past hour well behind the surface cold front.

As shown in the meteogram below, the winds at the Salt Lake City airport shifted from southeasterly to northerly from 0730–0940 MST this morning.

However, the frontal snowband developed well behind this surface front.  One can see it filling in over the southern Great Salt Lake, well behind the surface front, at 1800 UTC/1100 MST (click to enlarge).

The frontal band is now over us at the University of Utah.  It should give us a couple of hours of entertainment, but should be out of the way come rush hour.

Olympic Warmth

Norwegian skier Chris Jespersen races in the 15 km cross country final (Getty Images)

If you are a ski junkie like me, you've probably been seeing some crazy stuff at this year's Olympics.  Temperatures have been ridiculously warm and this has clearly had an impact upon the events.  It's too bad that NBC has ice skating on the brain.  With a little thought and marketing they could easily take advantage of the scantily clad uber-athletic cross country skiers to boost ratings.

American Sophie Caldwell in the 10 km classical final (AP Photo Matthias Schrader)

Everyone races in the same conditions (for the most part, although warmer snow typically deteriorates more quickly, resulting in a bigger handicap for later skiers than occurs in cold weather), but this is the Winter Olympics, not the Spring Olympics, and I miss seeing races on cold, fast snow.  The problem with Sochi is that it has a somewhat maritime snow climate that is susceptible to thaws and rain.  They could have gotten lucky and had a cold pattern set up for the games, but when you put the Olympics in areas with maritime snow climates, this is what can happen.  

Sochi has an average high in February of 50ºF.  That's even with Seattle's Feb high and four degrees warmer than Vancouver where the games were held in 2010.  Altitudes in the Sochi Mountain Cluster, which includes the Laura Cross Country Center and the Rosa Khutor Alpine Resort range from about 2,000 feet to 6,500 feet.  Thus, this is like holding an Olympics in the Washington Cascades (Snoqualmie Pass is 3,000 feet), except the sun is even higher since Sochi is at 43ºN.  

My guess is that the high mucky mucks who run and sponsor the olympics love the warm weather, but most of the athletes don't.  You can bet that the Norwegian cross country team, which has fallen well below expectations in this games, can't wait to see the Olympics in a colder climate.  The good news is that Pyeongchang, South Korea, is climatologically several degrees colder than Sochi in February, although I suspect they have their own share of weather concerns, as does any Olympic city.  

Contenders for the 2022 games (Oslo, Norway; Krakow, Poland; Almat, Kazakhstan; Lviv, Ukraine; Beijing, China) are colder still, with the exception of Beijing, although the outdoor venues would be in Zhangjiakou, which as an average February high of only 35F.  Let the bidding for a real winter Olympics begin...

Big Graupel

Yesterday (Saturday) afternoon's convective storms produced some thundersnow and some big graupel, the latter still quite apparent on the hill today (Sunday), including these samples from Alta's High Rustler.

I often tell people that when it comes to resort skiing, I prefer graupel over cold smoke.  Graupel is high density and makes the steeps smooth as a baby's bottom.  Unlike high density wet snow, it lacks cohesion and is quite supportive.  Yesterday's storm produced 3 inches of snow with 0.42 inches of water.  That's a water content of 14%.  No need to thumb your noses at such high water contents as a few inches of graupel skis great.

The blogger's son knows a good thing when he skis it and doesn't thumb his nose at a good graupelfest

Yesterday's big graupel was the result of several factors.  One was the intensity of the convection.  Strong updrafts help to keep larger particles lofted longer, allowing them to grow to larger sizes.  Another was the warmth of the storm.  Warm storms typically have more supercooled liquid water, which is what coats small ice crystals to form graupel.

Storms like yesterday's might not produce the Greatest Snow on Earth for some, but it is just fine by me.

The Great Warming

If you like April, our current pattern is for you.  Minimum temperatures the past couple of days have been near typical highs and both maximum and minimum temperatures are more typical of what one sees in mid April than mid February.  

Source: NWS

Alta-Collins currently sits at 95 inches, within reach of the coveted 100 inch base mark.  It's great to have some cover finally, at least at upper elevations.  It looks like we may crack 100 in the coming week.  

More Cascade Concrete, Then More Warming

Looks like about 1.2 inches of snow-water equivalent at the Alta-Collins observing site so far during this event.

Source: MesoWest

Although earlier model runs called for things to taper off later today, this morning's call for periods of heavy precipitation to continue through Friday with the 12-km NAM generating another 0.7 inches of snow water equivalent by late Friday (see lower left hand panel below). 

Source: http://weather.utah.edu

Then we will have a very warm weekend - afternoon ridge-top temperatures at 11,000 feet are forecast to be in the low 30s.  Bring wax and sunblock for the resorts and enjoy a long and leisurely lunch.  Given the heinous avalanche conditions and what looks to be anything but the Greatest Snow on Earth on lower angle terrain,  the best option for backcountry skiers might be heading south to Zion or Moab for mountain biking, hiking, or rock climbing.

Deja Vu All Over Again

That's my favorite post title when we are in a stormy pattern and it still appears like we are on track for another pasting related to the inland penetration of another potent atmospheric river, as discussed in previous posts.  As I write this at 10 am MST, snow is falling at upper elevations in the mountains and we have a classic "cloud storm" scenario in the Salt Lake Valley in which the sky is full of virga, but just a few raindrops are surviving to reach the ground.

This morning's "cloud storm" from the Salt Lake City International Airport

This cloud storm scenario occurs when the moisture and dynamics for precipitation development are elevated and we have dry air at low levels, as can be seen in this morning's sounding.  

Source: NCAR/RAL

Forecasts are largely on track from yesterday with atmospheric-river-related precipitation spreading into northern Utah today and persisting through tomorrow.  In the upper Cottonwoods, the model forecasts are actually a bit wetter than yesterday's, with this morning's 12-km NAM generating 1.75 inches of water by 5 PM tomorrow (Thursday).  Such water totals might be on the high side, but something in the 1-1.75 inch range for Alta-Collins seems like a good bet.  Most of this will fall as high-density snow at upper elevations with snow levels rising to perhaps 8000 feet.   

Source: http://weather.utah.edu

Yup, another Cascadian experience, but it skied well last weekend.  Ski it if it's white.  

The Next Atmospheric River

Our second atmospheric river event in a week's time is setting up over the Pacific Ocean with a tremendous export of tropical moisture from the area near Hawaii streaming northward toward the Pacific Northwest.

1800 UTC 9 Feb – 1800 UTC 11 Feb 2014 GFS analysis of 925 mb wind (vectors) and integrated water vapor (mm, color contours with warmer colors indicating higher values).  

Over the next 36 hours, the atmospheric river will move eastward and sag southward.  By 5 PM tomorrow (Wednesday) afternoon, the axis of strongest water vapor transport will be draped across southern Idaho and Wyoming.  As was the case with the atmospheric river event this past weekend, the strength of the water vapor transport over the interior will be unusually high for this time of year with a frequency of occurrence during this 3 week period of about once every 5 years or rarer.

It certainly looks like the upper-elevation mountains of southern Idaho and western Wyoming are going to get another pasting, as indicated by the GFS accumulated precipitation through Saturday morning.

As you might deduce from the plot above, the mountains of northern Utah sit on the southern periphery of the heaviest 4-day accumulated precipitation in the current model forecasts.  Nevertheless, this does look like another significant event for the northern Wasatch and the Bear River Range (although not as big as the previous storm), with the Cottonwoods and southern Wasatch likely seeing their most significant precipitation late Wednesday and Thursday when the AR dips southward.  

This is also going to be another warm event thanks to the Hawaiian connection.  Direct output from the 12-km NAM (below) suggests rising ridge-top temperatures on Wednesday with the snow-to-liquid ratio dropping to less than 10 (i.e., more than 10% water content).  Snow levels will also rise to close to 8000 feet in the Cottonwoods.  Provided we only get a brief visit by the AR, as presently forecast, water totals in the Cottonwoods will be much lower than we saw during the last event, although snow and snow water equivalent rates could be strong at times late Wednesday and Thursday.  

If you don't like these Cascadian conditions, wait a couple of days and head to Zion on Friday to enjoy some 70 degree sun.  

Welcome to Seattle!

A drippy, foggy Monday morning in Salt Lake City

This morning dawned with Seattle-like rain and fog in the Salt Lake Valley and Cascade-like conditions in the Wasatch Mountains where high-density snow continues to pile up in the upper elevations.  Water and snow storm totals reported on the Utah Avalanche Center web site this morning range from 2.87"/30" at Alta to 46"/6.94" at Sundance.  Logan and American Fork Canyons remain closed and tragically, two deaths have occurred in backcountry avalanches.  

The storm should wind down today, with a break in the action tomorrow.  Beyond that, I hope you like the Northwest weather as we're going to get more of it.  A broad, low amplitude ridge remains over the region throughout the week, with another push of moisture into the northern mountains likely late Wednesday and Thursday.  Yes, it will be another atmospheric river event, with the tongue of tropical moisture that will be coming our way beginning to surge northeastward near Hawaii (westernmost arrow), just upstream of the remnants of the atmospheric river that gave us the deluge the past few days (easternmost arrow).  

GFS Integrated Water Vapor (mm, warmer colors indicate higher values) at 1200 UTC 10 Feb 2013.

If things come together as currently projected by the models, that will mean another round of rain for the valleys and high-density snow for the mountains.  The biggest uncertainty in this forecast concerns the position of the atmospheric river as a slight shift to the north or south can make a big difference for water/snow totals.  After that, the models call for the ridge to amplify somewhat with dry conditions but very warm temperatures on Friday.  

The GFS forecast time series shown below summarizes the situation.  Note in particular the heavy precipitation late Wednesday into Thursday (bottom left panel) and then the big warmup thereafter with temperatures on Mt. Baldy (11,000 ft) going into solidly into the 30s (upper left panel).  The GFS typically overestimates snow levels so don't panic about them going to almost 10,000 feet on Wedensday (upper right), but it is going to be a warm storm, so expect snow levels to be pushing 8000 feet.

Source: http://weather.utah.edu

Looks like an investment in Gore-Tex or Hefty bags might be in order.  A pair of ultra-fat fully rockered skis would be nice too.  

Positively Cascadian

Before discussing the balmy nature of the weather this morning, here's a very quick rundown of the water totals produced by the storm since 5 AM Thursday based on my eyeball estimates:

Tony Grove Lake (8474 ft): 6.6 inches (Logan Area Mountains)
Ben Lomond Peak (8000 ft): 6.2 inches (Ogden Area Mountains)
Snowbasin Middle Bowl (7400 ft): 3.5 inches (Ogden Area Mountains)
Alta-Collins (9662 ft): 2.3 inches (Salt Lake Area Mountains)

I don't have much faith in any of the automated stations in Big Cottonwood Canyon that measure snow water equivalent, but the Utah Avalanche Center reports 3.21 inches for whatever site they are using (probably manual measurements from one of the resorts), so we will go with that.

The Snowbasin-Middle Bowl and Alta-Collins observing sites are two of the most reliable in the Wasatch and they pretty much tell the tale for this storm.  Temperatures have risen dramatically through the period and are now a Cascade-like 35ºF at Snowbasin Middle Bowl and 27ºF at Alta-Collins.

Thus, we're probably seeing a snow level somewhere near 8000 feet in the central and northern Wasatch and a freezing level near about 8500 feet.  That huge temperature increase means a transition from lower to higher density snow as well as from snow to rain at below 8000 feet during the storm.  Ski conditions today should be "interesting."  Perhaps nobody will care about the Cascadian conditions since beggars can't be choosers.  

One of the interesting aspects of this event is that it has come in waves, despite the fact that the models called for relatively steady precipitation rates.  You can see this in the data from both Snowbasin-Middle Bowl and Alta-Collins.

Clearly we have some work to do to improve our modeling and prediction of these variations in precipitation rate as they are critical for avalanche mitigation efforts along highways at at the resorts and for people like me who are simply hoping to ski when it is snowing the hardest. 

A Good Day with More to Come

Finally!

It was great to get in some storm skiing this afternoon.  Snowfall rates at Alta were pretty much pegged at about an inch an hour from 9 am to 4 pm.

Source: MesoWest. 

Looks like Alta-Collins is now up to 1.5 inches of water 17 inches of snow for the storm total and climbing.  

I heard the lift lines were long in the morning, but I skied in the afternoon when the crowds were tolerable and the steady snow made for fun turns.  I even ran into a few members of the University of Utah Snow Study Team who having returned from the Tug Hill Plateau are trying to rack up as much vertical as possible.    

Of course, the best way to finish a ski day is to come home and see the radar lit up upstream.  Voila!

Source: NCAR/RAL

Yup, things are looking good for more snow, courtesy of this latest atmospheric river.  Enjoy!