Friday, March 31, 2023

We Need This to Stop

I never thought I'd say this, but we need this to stop.  We need the onslaught of storms to end, for the snowpack to settle, and for spring to begin.  

Snowdepths and snowfall amounts right now are just ridiculous.  Let's start at the Ben Lomond Peak SNOTEL, which is at an elevation of only 7688 ft (I'm not sure why it says 8000 ft in the figure below).  Snowpack water equivalent at that site is now 78.7 inches, the highest on record, easily toping the 74.0" observed in 1984 (yes, 1984 at this site was higher than 1983).  

A meteorologist friend of mine was wondering if this might be the highest snowpack water equivalent ever observed in Utah.  I suspect that's likely.  Perhaps someone out there can do some digging.  

Down in the Cottonwoods, the Mill D North SNOTEL is now at 51.7", well above the prior 2011 record of 44.3".  Records here, however, only go back to 1989 and don't cover those big early 1980s years.   

Perhaps most relevant to what I want to talk about here is how steep the snowpack water equivalent has been rising at these and other sites.  Mother Nature has added over 10" of water to the snowpack since March 15th.  Snowbird has also added a bit over 10" of water since that time.  Talk about load and stress!  

Meanwhile, the Alta-Collins site picked up 19" of snow from 9 PM last night to 7 AM this morning, including a 6" increase from 1 to 1 AM.  This is on top of the 14" that fell the previous night.  Total snowfall for the season is now over


Insane.  They are also well over 200 inches for the month.  I'm not sure what the resort record is, but the Alta-Guard snowfall record for a month is 244.5" set in December 1983.  We must be getting close to that.  

All of this puts us deep into outlier territory.  Readers of this blog know that I like to say beware when the atmosphere is in outlier mode.  I woke up this morning, saw the huge snowfall numbers, and looked at the forecast and got a pit in my stomach.  An incredibly deep snowpack.  So much new snow.  Slide paths that are greased. 

And then I looked at the forecast and saw the GFS, after a break tomorrow, was forecasting over 3" of water and 40" of snow for Sunday through Tuesday.  

Then I about threw up.  The NAEFS mean is lower and around 2" of SWE, but still a significant event.  

This must stop now.  Both canyons are currently closed.  The UDOT Cottonwood Canyons site reported that a natural bank sluff hit the road this morning.  They are extending the estimated time of opening (ETO) now to 11 AM.  The last I looked, there is no ETO for Little Cottonwood.  Snow safety crews have been working the ragged edge all season, but especially over the last month.  Avalanche threats exist not only in the Cottonwoods, but also along other highways where such slides are less common and only occur in big years.  

And we haven't even talked about the runoff.  

I am hoping we get through this cycle without incident and that after that we see a shift to something resembling spring with some longer breaks between storms.  Both the GFS and the ECMWF are advertising a high-amplitude ridge to develop along the Pacific Coast by later next week and be parked there by 0000 UTC 10 April (6 PM MDT Sunday).  

Let's hope it happens. 

Thursday, March 30, 2023

What the Hell Is Going On?

A lot of people have requested a blog post explaining what the hell has been going on this winter.  Well here goes.

I don't know.

At least that's the tl;dr summary.

OK, I can do a little better than that, but explaining the whims of the atmosphere is very difficult and I don't want to suggest that I'm some sort of mystic who knows what is going on.  I'm not sure anyone is.  

Let's start in the fall.  As usual, a variety of seasonal outlooks were issued by various groups.  These always get a lot of attention, but their value is often limited.  

I will use the official forecast issued by the National Weather Service Climate Prediction Center as example.  Below is the three-month outlook issued in November for December through February.  Due to the presence of La Nina (which has now waned), the forecast suggested that the dice were loaded for a dry southwest and a wet northwest.  Utah could go either way.  

Mother Nature, however, had different ideas, and for the mountain west, basically flipped that forecast on its head, producing a wet southwest and a dry northwest.  

Mother Nature 1, NWS Forecasters 0.

To be fair, the forecasts issued by the Climate Prediction Center are probabilistic.  They don't say that the southwest will be dry and the northwest wet. Instead, they forecast a shift in the likelihood of possible outcomes. Pure chance for any given winter gives a 33.3% chance of above, near median, or below median precipitation (in this case, median is broadly defined as a range around median).  Equal chances, as was forecast for Utah, says there's no loading of the dice and they simply don't know what is going to happen.  Below median, as was forecast for the southwest, indicates a shift to something like a 25% chance of above median, 35% of near median, and 40% of below median (the exact numbers vary somewhat regionally).  Thus, the seasonal outlooks issued by the National Weather Service in November predicted a small shift from chance toward drier conditions in the southwest, although they are often interpreted or communicated in ways that make them seem more confident.  

Long-lead-time forecasts, such as seasonal outlooks like the one above, are based largely on forecasts of more slowly varying components of the Earth's climate system that exhibit some predictability (over chance) at long lead times.  For example, although the day-to-day weather cannot be reliably predicted after about two weeks, ocean temperatures in the tropical Pacific (e.g., La Niña or El Niño) exhibit some predictability at long lead times.  

The outlook above was based largely on the presence and anticipated persistence of La Niña for this winter.  Forecasts probabilities of above, near, or below median precipitation were based largely on what happened during past La Niña, with some consulting of computer models forecasts and expert judgment.  

This sounds straightforward, but the the Earth is a complicated place.  First, although we can anticipate La Niña with some skill, the forecasts aren't perfect or highly detailed.  During La Niña the central and/or eastern tropical Pacific cools to below average, but the strength and coverage of the cold water varies.  This in turn affects the distribution of thunderstorms and thunderstorm complexes in the tropical Pacific and in turn that  affects the atmospheric circulation in different ways.  

Then there is the inherent randomness of weather and weather systems.  Waves and other flow patterns in the atmosphere can be highly chaotic.  Think of a loose firehose.  You can see there are waves in the hose, and they tend to exhibit preferred wavelengths and amplitudes, but there's also a lot of randomness.  A firehose is relatively simple compared to the complex three-dimensional flows in the atmosphere where there are interactions between circulations near the surface and at upper levels and between the tropics, midlatitudes, and polar regions.  

The existence of La Niña and other slowly varying characteristics of the Earth's surface (e.g., Arctic ice coverage, etc.) can affect some characteristics of the large-scale flow pattern, but there's still a lot of random stuff happening.  How the atmosphere got the way it did during the 2022/23 winter is complicated, much like Harry Potter finding the sword of Godric Gryffindor.

With that in mind, let's look at the atmospheric circulation over the past few months.  To do this we will use analyses of 500-mb height anomalies.  The 500-mb level is often used to describe the upper-level flow pattern.  Areas with positive height anomalies are places where there were anomalously high heights and ridging at upper levels. Areas with negative height anomalies are places where there were anomalously low heights and troughing at upper levels.

The 90-day height anomaly for October 4 to January 1 shows an anomalous tough over northeast Siberia (cool shading), a monster anomalous ridge over the North Pacific centered near the Aleutian Islands (warm shading), and a weak anomalous trough over the interior western US.


For November 4 to February 1, the location and amplitude of these shift some, but the general pattern remains the same.  Anomalous troughing remains over Siberia, ridging near the Aleutians, and troughing over the western US.  


And for December 2 to March 1, the story remains largely the same. 


And suppose we looked at the 30 day period ending in mid March (our current pattern still approximates this).  Apologies for the color pattern change, but lo and behold, anomalous troughing over northeast Siberia (perhaps shifted a bit northward), ridging near the Aleutians, troughing over the western United States (and Canada).

So, this general pattern of a trough over northeast Siberia, a ridge over the north Pacific, and a trough over the western US has been locked in for the better part of the winter.  Overall, this pattern resembles something known as the negative phase of the Pacific-North American Pattern, or negative PNA, which is one of the leading patterns of atmospheric variability in the north Pacific and North America.  

Scientists have created an index to measure the strength of the PNA pattern.  Below is a graph illustrating 3-month averages of this index from 1950 through February 2023.  The PNA index tends to flop fro positive to negative.  This winter we have indeed been in a negative phase of the PNA pattern.  

All of this is well and good, but it is where I am going to get off this train and here's why.  First, the negative PNA pattern is associated with La Niña, so that makes some sense.  However, La Niña weights the dice toward a drier southwest, which didn't happen this season.  Something else is going on with the large-scale circulation and one index, like PNA, doesn't tell us enough.  There's a lot happening in the Earth's climate system globally that might shift the PNA pattern characteristics or perhaps randomness played an important roll this season.  People who are smarter than me and specialize in the large-scale circulation can perhaps answer these questions, but I can't.  

As Tom Petty sang, "baby even the losers get lucky sometimes" and boy did we get lucky this winter.  

Damn the Torpedoes. 

Tuesday, March 28, 2023

Optimism for the Corn Harvest

March is winding down and what a run of cold storms we have had.  How long they continue, I don't know but I was thinking that this spring has serious potential for a major corn harvest if the weather cooperates.

First, the snowpack is enormous and it is enormous on every aspect at at all elevations.  We're not limping into spring as we have frequently over the past several years.  The ability to follow the sun, work the softening snow on differing aspects, and to have relatively easy access to adventurous terrain could be as good as it gets this spring.

Second, we have had so much snow this month that any dust layers are buried deep in the snowpack and will take some time to emerge.  Many years we have a dust emerging quickly in either March or April.  An example below from 2018.

Thus, I am optimistic for the corn harvest, but the wildcard is the weather and perhaps the timing of strong south wind events with agricultural activities that disturb the land surface.  It's helpful that it has been so wet this year, but lowland soils can desiccate quickly and agricultural fields can be huge emitters.  We have seen examples of enormous dust emissions from tilled fields in the Cedar Valley in April (see Where Today's Dust Is Really Coming From (Not Sevier Lake) from April 2018).  Such an event would sadly put a big dust layer on top of all this wonderful snow. 

Let's hope for a great transition from powder to white corn, without any snirty dancing on dust until late in the spring.  

Sunday, March 26, 2023

I'm Exhausted But Thankful

What a run of weather, and it ain't over yet.

I decided I could not miss out on this one-in-a-generation pattern and skied Friday, Saturday, and Sunday.  My brain is basically whitewashed at this point.  My waking hours have been in a snow globe.  Friday and Sunday I toured.  Saturday I racked up an enormous amount of lift-served vertical given my fragile back.  I'm exhausted.

Thank God tomorrow is Monday.  

Seasonal snowfall records have fallen at nearly all of the resorts.  It's well known that this blog has an Alta bias, so we'll give them a hat tip for breaking their record since 1980. 

In all likelihood, that's an all-timer, but we should probably wait for the Alta Guard reports to come in since records there go back to the 1940s (although the site hasn't always been in exactly the same location.

Also getting news is that the statewide average SNOTEL water equivalent is also at an all time high.  This record has an asterisk.  In particular, the sites used have changed from 59 sites in 1981 to 114 today.  Thus, the elevations and spatial locations of new sites could have affected trends in the average.   

It is also important to recognize that the statewide average being at an all-time high doesn't necessarily mean that every drainage is at an all time high.  Snowbird, for example, is at a record high for the date (records begin in 1990), but is still more than 10 inches below its all time record.

So, let's be careful about thinking this year will be like the 1983 flooding down State Street because the statewide average is at a record.  We certainly are concerned about the runoff, but much will depend on what happens over the next few weeks.  Additionally, there have been important infrastructure upgrades since 1983.

Let's forget graphs for a while and look at some pictures.  It's been a while since I've been above the S-curves in Big Cottonwood.  What a scene!  How about this snowbank at Spruces?

Bus anyone? 

Good luck finding your cabin in Mill D after the next storm.  

Someone shovel this roof before it collapses and makes a mess!

Meanwhile, on north aspects, I have friends that call this FM100 Easy Listening Skiing

The snowpack is so deep that in some areas that it's up into the aspen canopy.  

You know all that crap I say about Steenburgh winter and the low-angle sun before February 10th?  It's so bloody cold that south aspects actually survived today.  It got just a little stiff, but you can't feel that in the pictures. 

Count your blessings that you are alive during the winter of 2022/23.  I can't tell you how fortunate I feel to have lived to ski this season. 

Friday, March 24, 2023

Deep Trouble

What an unbelievable season.  It just keeps coming.  McKenzie Skiles, a snow hydrologist here at the University of Utah, tweeted the photos below taken by Otto Lang of the Atwater snow study site above the Town of Alta.  Multiple groups have instruments on the platform, including a profiling radar from my group (that's the dish).  What a snowpack!

I attempted to ski tour this morning, but really, the snow was too deep for the hill we were on.  The pictures looked good though.

Photo: Michael Wasserstein

It snowed hard for the entire 3500 vertical foot climb and I arrived at the top as a frozen wet sponge.  I'm still shivering!  It's late March and the snow was cold and in pretty good condition even at low elevations.  Melt-freeze crusts?  Perhaps buried, but not really an issue.  Did I say it was late March?  What a season.

We exited Mill Creek into the wall of snow associated with a strong snow squall.  Visibility less than a quarter of a mile and rapidly deteriorating road condition.  

Every day I look at the models and wonder when this will end.  I don't know.  Here's the latest downscaled NAEFS for Alta.  A mean of more than 3" of water for the next week.  

Our radar is in "Deep" trouble.

Wednesday, March 22, 2023

It May Never Stop

Do you ever wonder what it would be like if it started snowing and never stopped?
- Steve Casimiro, Editor, Powder Magazine, 1987-1998 

It's been a long week at the HAARP Weather Control Center.  About a month ago, someone "discovered" that the Sierra-Wasatch snowstorm lever was locked at 11.  Nobody knows who did it or when it happened, but it is jammed.  They've tried shifting other levers to control the storm track over the past month, to no avail.  

Weather and snow-depth sensors in the Wasatch are starting to disappear, like this one at Snowbird (photo from Sunday, 19 March). 

The medium-range forecasts are clued in on this and continue to provide a parade of storms for the Wasatch Range.  Last night Alta picked up another 7 inches, with their total snow depth hitting 190 inches at 6 AM this morning.  The models continue to advertise more snow for today with the HRRR producing 1.27" of water and 15.4" of snow at Alta-Collins from 6 AM this morning to 9 AM tomorrow morning and the GFS 0.9" of water and 12" of snow.  

Let's go with 12-18" and hope that comes through.  No need to hope for more when the models are in the Goldilocks range. 

Time for blogging has been limited this week.  I've been quite occupied with the day job.  If you see me on campus, treat me like one of this season's cornices and give me a wide berth.  Grumpiness abounds. 

Saturday, March 18, 2023

Snowpack Observations

What an incredible season it has been.  A few observations from around the area.

I took the photo below of Mineral Fork yesterday morning from the Wildcat Ridge between Big Cottonwood and Mill Creek Canyon.  What struck me most as I looked into that area (and my eyes have better "resolution" than this blown up phone photo) was the lack of pucker trees and brush.  Nearly everything is buried, including on the mid-canyon slopes.  

Similarly, the main Porter slide path has only sparse tree coverage.  

In lower snow periods, that path has gotten quite choked up with trees over the years, but that's not an issue currently.  Similarly, a lot of lower-to-mid elevation treed and brushy areas have great coverage and many areas with difficult brushwhacking are pretty easy to move through.  

Below is a non-scientific comparison of the snowpack this season to that in 2010/11 at 6600 ft in Porter Fork.  I did some offline measurements and the photo I took yesterday might have be bit more roof snow in it than the one from 2010/11, but the latter was taken 11 days earlier.  

From Mount Timpanogos north to Ben Lomond Peak, here is where the current snowpack water equivalent ranks at SNOTEL stations with long periods of record:

Timpanogos Divide: #1 out of 45 years
Snowbird: #1 out of 34 years
Brighton: #1 out of 37 years
Thaynes Canyon (PCMR): #2 out of 34 years
Mill D North: #1 out of 34 years
Parleys Summit #2 out of 45 years
Louis Meadow: #1 out of 24 years
Lookout Peak: #1 out of 35 years
Hardscrabble: #1 out of 30 years
Parish Creek #1 out of 24 years
Farmington: #3 out of 45 years
Farmington Lower: #1 out of 20 years
Ben Lomond Peak: #3 out of 45 years
Ben Lomond Trail: #1 out of 43 years

Simply incredible, and there's nothing to suggest the parade of storms is going to slow down anytime soon.  The medium-range guidance continues to look active. 

I have been and might still be a bit reluctant to rate this season ahead of 2010/11 for skiing, but if you want to argue otherwise, so be it.  I'm a little partial to 2010/11 because although the snow accumulation started a bit later that year, there wasn't a persistent weak layer issue for as long as earlier this year.  It is also possible that I'm biased by the fact that I had a more functional body then.  In either event, we're splitting hairs.  

Thursday, March 16, 2023

Break in the Storms

All is quiet for now on the western front.  Yesterday's storm is off wreaking havoc in Colorado and the high plains and, believe it or not, we are in split flow today with the GFS forecast valid at 1800 UTC 16 March (Noon MDT Thursday) showing two branches of the jet, one moving over the ridge centered over the Pacific Northwest and British Columbia and the other around a broad trough over the Southwest, with Utah in the middle.  

That general pattern predominates through the weekend as the GFS forecast valid 0000 UTC 20 March (6 PM MDT Sunday) continues to feature weak flow over Utah with one branch of the jet moving up and through northern Canada and the other plunging down through Mexico.  

If you had to summarize a pattern like this in one word it would probably be fair.  A few weak systems will move through the split, but for the most part skies will either feature high clouds or be clear.  Unlike a high-amplitude ridge, which would result in above average temperatures, temperatures will be a bit below or near seasonal norms. The 700-mb (crest-level) temperatures this afternoon and Friday will be around -10C and Saturday and Sunday around -6C to -7C.  Average for this time of year is about -5C.  That will help with powder preservation, but it is mid March and the sun is getting intense so I'd expect a melt-freeze cycle on the southern half of the compass, western aspects, and low-and-mid elevation terrain.  The lower temps will help some with powder preservation today and tomorrow, but you can't stop the sun.  

There is another possible warm, windy storm next week.  Stay tuned.

Monday, March 13, 2023

The Next Storm

The parade of warm and windy storms continues this week.  Today and tonight we may see a mountain snowshower at times, but it won't add up to much.  

Tomorrow afternoon is when things begin to get interesting.  The GFS forecast for 0000 UTC 15 March (6 PM MDT Tuesday) shows a Pacific cyclone moving across northern Nevada with the trailing frontal trough extending across northern California and the Bay Area and the accompanying atmospheric river producing moderate vapor transport across southern and central California.  

The lower right-hand panel in the GFS forecast above is an analysis of integrated vapor transport (IVT) magnitude (color fill) and vectors.  Note that the strength of the atmospheric river, as indicated by the magnitude of IVT, declines with inland extent, as is often the case. This occurs due to the loss of water vapor to precipitation.  These losses are especially large over the high Sierra south of Lake Tahoe, which is why there is often minimum downstream of that high barrier over Nevada, as is the case in the GFS forecast above.

During this period, Utah is in strong southerly flow.  This pattern persists through 1200 UTC 15 March (6 AM Wednesday).  The IVT in Utah is generally near or just below low-end atmospheric river magnitude (250 kg/m/s; yellow shading) through this period.  

Thus, we would expect periods of valley rain and mountain snow late tomorrow and tomorrow night.  The models do differ quite a bit on amounts during this period.  For example, from 12 PM MDT Tuesday to 6 AM MDT Wednesday, the 6Z GFS produces 0.41" of water equivalent and 2.9" of of high-density snow for Alta Collins.  In contrast, the 12Z HRRR produces 1.32" of water and 7.9" of high-density snow.  

I suspect the fundamental difference in this case is topography, with the finer-scale HRRR topography yielding more precipitation than the GFS.  That said, we have seen the HRRR overproduce sometimes in situations like this in which the synoptic forcing (e.g., associated with fronts) is weak.  That's not a guarantee, however.  I'm inclined to go with something like 5-10" of high density snow for Tuesday afternoon through 6 AM Wednesday, using the HRRR as near-upper-end guidance.    

But wait, that's not the end of the storm.  During the day on Wednesday, the main upper-level trough and cold front move through.  The GFS currently puts the trough at crest level right over northern Utah at 2100 UTC 15 March (3 PM Wednesday).  The ECMWF HRES has similar timing (not shown).

As things look now, this has the makings of a good day for storm skiing on Wednesday.  The GFS is really cranking out the precipitation during the day on Wednesday.

Overall, this looks to be a higher-density storm.  We might end with some low-density snow on Wednesday if we don't shift to graupel (although I like graupel, so either way its a win).  

Bottom line is that more snow is coming.  Enjoy.  

Friday, March 10, 2023

Gone with the Wind

Given that it is the U's spring break, I was fortunate to be able to get away for a ski tour yesterday.  It was a spectacular day, with fantastic snow and great skiing.  

The Wasatch looked amazing.  The snowpack is deep and the cover extensive.  It's the time of year when the north aspects are beginning to emerge from 24-hour shade and see the sun, making the views even more impressive.  A group of four clearly had a nice run down Stairs Gulch early yesterday.  

I spent most of the day reminiscing about what a great season it has been so far and what a remarkable run of cold snow and cold powder we have had.

As we discussed for several days, the storm track is shifting and we are moving to a warmer and windier pattern.  Indeed, except perhaps in a few highly wind-protected spots, yesterday's powder is now gone with the wind.  Gusts overnight reached over 90 miles per hour at ridge-top locations.  Temperatures have climbed to near freezing at 7500 feet already.  There may still be some good mid-elevation powder on north aspects in a few places, but the damage is being done from the top down and the bottom up.  

On the plus side, there is a storm brewing for today and tonight.  The two key ingredients are strong vapor transport associated with an inland penetrating atmospheric river and a frontal pushing in from the west.  At 0000 UTC 11 March (5 PM MST Friday), the atmospheric river is draped over northern Utah just ahead of the front.  

By 0600 UTC 11 March (11 PM Friday) the front is just south of the Cottonwoods.  

And by tomorrow morning it is through and we are post-frontal, although this is not a situation we would expect the Alta post-frontal magic to kick in as it's simply not unstable enough to generate orographic or lake-effect snow showers tomorrow morning.  

Looking at our GFS and HRRR derived forecasts provides a decent look at the range of possibilities between now and tomorrow morning.  The GFS  cals for mild conditions today and through this evening with Mt. Baldy (11,000 ft) temperatures in the low 20s and the wet-bulb zero level near or just above 8000', which would indicate a snow level near or just above 7000 feet.  Snow-to-liquid ratios are between 5 and 9 during this period, meaning high-density snow at upper elevations with periods of light precipitation.  After this evening, temperatures and the wet-bulb zero drop and snow ratios increase.  For Alta-Collins, the GFS generates 0.89" of water and 7.3" of snow through tomorrow morning.  

The HRRR is warmer and wetter.  It pushes temperatures on Mt. Baldy to 25˚F this afternoon and the wet-bulb zero level to 9000 feet, which would result in a snow level that flirts with the base of Snowbird and Alta.  It is also wetter today and with the frontal passage, generating 1.77 inches of water and 12.3" of snow for Alta-Collins through tomorrow morning.  

My synopsis is that these two model forecasts probably represent a reasonable range for the forecast through tomorrow morning, so my expectation is for 0.8 to 1.8" of water and 7-14" of snow at Alta-Collins by 8 am tomorrow.  Then the storm will be over.  This will be high-density snow and ski quality will probably depend on how much snow comes in the later stages of the cold-frontal passage when snow-to-liquid ratios are higher.  More snow then would at least give a right-side up profile.  

At lower elevations, expect rain today and this evening.  Some snow is possible on the benches or even on the valley floor late in the frontal passage tonight, but it won't add up to much. 

As most of you have probably heard, two skiers were buried in an avalanche yesterday in the Uintas, with one killed.  A preliminary report is available here.  I share my deepest condolences with their friends and family.  

Wednesday, March 8, 2023

January in March Is Coming to an End

The pattern over the last couple of weeks has been a really great one for late February and early March with lots of cold storms and high-quality snow.  Many mid-elevation areas have a remarkably deep snowpack right now and outstanding ski conditions.  Sure the snowpack is deepest in Little Cottonwood, but I had a meeting in Park City yesterday and was blown away by the amount of snow in town.  I had time for a few laps at Deer Valley and couldn't help but take a photo of the towering snowbank at the top of Sultan.  This is an area that is heavily windloaded, but still, very impressive.  

The view eastward showed a frozen Jordanelle Reservoir and nothing but snow-covered landscape.  Even the south aspects and under-development Mayflower resort have snow.  What a season!

Ski conditions were outstanding with a few inches of cold powder.  It felt like January, but with an epic late season base.  

Change is coming though as we will transition to a warmer pattern later this week.  For tomorrow, however, there is one last cold-powder refresh coming, with a weak trough moving through later today and tonight.  By 1500 UTC (8 AM MST) tomorrow, the 6Z HRRR is putting out about 7" for Alta, just over 5" for Canyons-Daybreak, and about 4" for Deer Valley-Ontario.  

The GFS is also right around 7" for Alta.  I'll call it a 6-12" refresh for Alta and hope we come in on the top of that range.  Additionally, snow-to-liqiud ratios for this one will continue to be higher than average.  

After that dump, change is coming. Temperatures will climb during the day on Thursday.  The next storm, slated for the Friday and Friday night, will be warmer and windier.  There will be snow, and it could ski quite well, but it will be a change from the cold events we've had of late.  Overall, the pattern will remain active, but shifted toward warm and windy events.  Nothing to complain about, but January in March is over after Thursday.   

Monday, March 6, 2023

You Ain' t Seen Nothin' Yet

We begin this Monday
The first day of spring break
With a little from BTO
Because as I look at the forecast
All I can think is
You Ain't Seen Na-Na-Nothin' Yet

The numbers for the past season, each month of the season, the past month, the past week, and even the past two days are astounding.  600+ inches of snow at Alta.  Another 15" last night.  Alta-Colllins snow depth at 7 am: 185 inches!

And our friends upstream in California?  The Central Sierra Snow Lab near Donner Pass reported yesterday that the've had a season total of 562", within a foot of the epic 2016/17 year total, with 2-4 feet in the forecast.  

But as crazy as you think this season has been, it's about to get crazier.

The recent pattern has been dominated by high-amplitude ridging over the north Pacific and a deep trough along the Pacific coast.  This has resulted in a series of cold storms across California, Nevada, Utah, etc.  The GFS analysis for yesterday morning (1200 UTC 5 March) shows this well.

That pattern will bring more snow for both California and Utah this coming work week, but change is coming.  As shown in the GFS forecast, by 1200 UTC 10 March (5 AM MST Friday), the subtropical Pacific Jet will extend across the eastern Pacific and onto the Pacific Coast where it merges with the polar jet dropping down from Alaska.  

This is an important shift in the pattern and the corresponding GFS regional forecast below shows a potent atmospheric river, what we would have once called the Pineapple Express, directed right at California with the parent cyclone making landfall over the Pacific Northwest and trailing cold front across California.  So, after all of this snow, we transition into a windy and warm storm pattern with 700-mb temperatures in the Tahoe area of -1˚C on Friday morning.  Sorry Tahoe, no more blower pow for you!

That system ultimately spreads into Utah giving us wind and warmth Friday night with a big system potentially following.  

It's a bit early to talk confidently about details, but let's take a look at what the GEFS ensemble is doing.  At the Central Sierra Snow Lab, after the snowfall during the work week, the downscaled NAEFS shows the action picking up around 6Z 10 March (11 PM MST Thursday).  There are, however, a wide range of forecasts.  Some only generate an inch or two of water equivalent (which when added to the precpitation since last night adds up to about 3" of water for the week) but some go off.  The mean for the week is about 7 inches of water and, this will be a warm storm.  Our snow-to-liquid ratio algorithm suggests ratios certainly less than 10:1 and some ensemble members call for rain at this 7000' elevation.  Batten down the hatches!

For Alta-Collins, one can also see significant spread after 6Z 10 March as much depends on the track of the storm and atmospheric river.  Regardless, over the 7-day period (including last night), most of the downscaled ensemble members are producing between 2 and 5 inches with a mean of just over 3. 

The low-end scenario is that the system tracks to the north and we get wind and warmth but not as much snow.  We still get a decent amount of snow.  2" of water equivalent and 20-25" of snow this week (including last night) would be at or just above what we would expect from climatology.  High end scenarios are more than double that.  

So, insanity to continue this week, but expect a change to a warmer pattern later in the week.  You ain't seen nothin' yet.  

Sunday, March 5, 2023

Mother Nature Can't Be Stopped!

Do you ever wonder what it would be like if it started snowing and never stopped?

- Steve Casimiro, Editor, Powder Magazine, 1987-1998 

The epic 2022/23 ski season continues. How I have wanted to write a sentence like that since the 2010/11 season!

I wasn't sure what to expect for yesterday, but lo and behold it turned out to be another pretty good day of ski touring. 

I got home and took a quick peek at the 18Z HRRR and it was only putting out about 0.37" of water and 4" of snow at Alta and I though maybe things wouldn't go off for Sunday.  Then at about 3 PM yesterday it started snowing.  Then i picked up to 2-3" per hour snowfall rates.  And by 8 PM there was 10" on the Collins stake.  Then it kept snowing.  They are now up to 21" based on the automated interval observations.

What can I say?  Mother Nature can't be stopped.  She continues to produce.  Total snow depth at Alta is now up to 178".  

Keep skiing.