Flirtin' with Disaster

As far as inversions and air pollution go, we've had a pretty good run this year.  Although November and the first half of December did not bring a lot of precipitation, a number of weak storms moved through northern Utah to keep things stirred up.  Since then, a progression of storms has also prevented persistent inversion events, limiting the severity and duration of poor air quality episodes.

That's all about to change.

The loop below tells the story well and covers analyses and forecasts for a one week period from 1200 UTC 1 Feb (0500 MST Monday 1 Feb) through 1200 UTC 8 Feb (0500 MST Monday 8 Feb).  At the beginning of the look, you can see the deep trough associated with last weekend's storm existing the state.  Then, we have another trough move through on the 4th (tomorrow), which will probably give us our last gasp of snow for a while (2-4 inches in the mountains).  Although there is a brush-by trough on the 6th and 7th, the long-term trend is for ridging along the west coast and, as far as ridges go, this one is a big one.

With snow on the ground in the valley, as far as air quality is concerned, we will be flirtin' with disaster.

The severity of the event will probably depend on two things.  The first is the strength of the brush-by on the 6th and 7th.  If we are fortunate, that brush-by will give a clean flush to the valley even if it doesn't bring much snow to the mountains.  If we're unfortunate, it will pass too far to the north.  The second is how long the high amplitude ridge will be around.  Although we have confidence in the development of the ridge, forecasts of its potential demise are far enough in the future that I don't want to speculate.  I suspect a best-case scenario is that we have a 4 day inversion event and just begin to flirt with values at or above the EPA clean-air act standard.

In the mountains next week, the ridge should produce the first extended period of warm weather and blue skies we've had in a while.  Conditions should be ideal for high-speed cruising at the resorts as it will be warm, but the sun still isn't high enough to trash the north aspects.  The backcountry snowpack, however, remains tricky, and will probably need to be treated as "guilty until proven innocent", as the Utah Avalanche Center said a few days ago.

One quick comment on the backcountry.  There are more people out than ever before.  Spooning is hard these days due to the great diversity of skis people are on, but keeping your tracks tight with your partner conserves the hill and leaves more powder for others to enjoy during dry spells.  A conserved hill is a happy hill.

Photo: "Steve the Cook"

Groundhog Day Seasonal Climate Musings

Today is that day when a bunch of old men in western Pennsylvania dress in weird costumes, pull a rodent out of a hole, and claim to forecast the weather for the upcoming spring.  Animal lovers may mildly object to the torturing of the poor groundhog, but meteorologists are horrified!

There will be no discussion of whether or not the groundhog sees his/her shadow and what that means for spring here.  Instead, we'll deal with evidence, knowledge, and predictability.  After that, then we'll guess.

Let's begin with a summary of the winter so far.  As most of you are aware, one of the strongest El Nino's on record was predicted to occur this winter and has materialized.  Outlooks issued in October showed better than climatological odds of below average precipitation during November-to-January in the Pacific Northwest and better than climatological odds of above average precipitation in the southwest.

Source: CPC

As far as mountain snowpack is concerned, the weighted dice have come through to some degree.  Most basins in the southwest are running near or above average (not sampled by SNOTEL is the southern Sierras, but they are at 107% of average) and the interior northwest is below average.  Northern Utah and the Wasatch are near average.

Source: NRCS

If you want to quibble, it would be in the Pacific Northwest, which is at average in most basins, and in the western Great Basin, which sits well above average.  It is worth remembering, however, that the outlooks above are probabilistic and areas in brown and green don't mean that above and below average are guaranteed.  They simply indicate where the dice are loaded.  For  climate projection, I rate the outlooks above as good, at least in terms of capturing the overall pattern, but not outstanding, especially when getting down to the basin scale.

Snowpack in the Wasatch sits about as close to median (the point where half the winters have more water equivalent and half have less) as you can get.

Source: NRCS

Here are a few numbers to back that up in terms of the percent of median on 1 February: Timp Divide 106%, Snowbird 107%, Brighton 107%, Thaynes Canyon 104%, Mill-D North 101%, Lookout Peak 111%, Parrish Creek 86% (an anomaly), Farmington 102%, Ben Lomond 94%.  In case you like average instead, at most sites, we sit at or just below average.  For example, Snowbird is 92% of average and Brighton 102%.

Bottom line: We're pretty much right in the middle of the climatological snowpack distribution. Some have called this an above-average ski season, but I think that perspective is strongly weighted by how crappy the past couple of years (especially last year) have been.  This year, we got off to a slow start and have been dealing with a tricky backcountry snowpack.  On the other hand, we've had a steady progression of storms since mid December, giving us regular refills and I've had a number of good powder days.  Overall, I rate the season as good, but not excellent.  

How about the rest of winter?  Well, the strong El Nino is expected to weaken by late spring or early summer, although there is some uncertainty in exactly when it will wane.  It appears, however, that El Nino conditions will hold through April, even if they might be weaker than the wintertime peak.  Based largely on correlations with past El Nino events and climate model forecasts for the late winter and early spring, the climate prediction center is going for a loading of the dice for above average precipitation in the southwest and below average in the northwest, although the transition zone is shifted a bit northward.  

Source: CPC

So, if you want to be an optimist, hang your hat on that very slight loading of the dice.

There is, however, a serious concern for us in the short term.  The models are calling for a major pattern shift to develop over the next several days, with persistent ridging developing over the western United States.  For example, the GFS has a monster ridge over the west at 150 hours.  

The Euro is similarly ridgy.  No need to panic yet, as much may depend on the position and strength of the ridge, but I'm a bit concerned about the pattern change that is presently being advertised.  Fortunately, we have a storm coming in for Thursday, before the ridge builds in earnest.  

PCMR Gets Some

Those of us who live on the western side of the Wasatch can frequently look down our noses at the paltry snowpack and snowfall in Park City, but not last night.

Overnight snowfall totals reported by the Utah Avalanche Center include 10" in upper BCC and along the Park City Ridge line and only 4" in Little Cottonwood Canyon.

The reason for this backwardness is the strong cyclone that moved across the southwest last night (which also brought some impressive snowfall totals to our friends in southern Utah).  For example, at 0700 UTC (0000 MST) last night, the 700-mb low-center was just north of Las Vegas, with a trough extending northeastward to Wyoming.  The result was southeasterly to easterly flow impinging on the Wasatch.

As a result, the Wasatch Back temporarily became the windward side of the Wasatch, with snowfall totals greatest near and east of the Wasatch Crest and the terrain in and around the middle and lower Cottonwoods receiving only spillover scraps.

Source: Secrets of the Greatest Snow on Earth

Combat Skiing

The Cottonwoods have always been popular, but this winter, things are completely out of control.  This was the scene at 10:15 AM at Solitude.  The lower lot was full.  Cars were parking up and down the road, and chaos ruled.

Another perspective, showing cars parked along the road presumably to the upper lot.

As Yogi Berra said, "Nobody goes there anymore, it's too crowded."  Traffic and red snakes aren't new to the Wasatch.  What is new is that this is happening every weekend.  The status quo has to change.

Fortunately, although the backcountry is busier than it used to be, the views haven't changed and remain spectacular.

And the snow is still the greatest on earth.  FM-100 Easy Listening Turns today.  Right-side up and smooth as silk.

Mildly DIsappointing Snow Totals Today

After heavy upper-elevation snowfall last night, mid elevation rain, and more snow expected today, we spent the afternoon "cowering in the aspens", avoiding avalanche terrain, and wondering why it wasn't snowing harder.

From yesterday afternoon to 5 PM this afternoon, Alta ended up with a total of 1.57" of water and 13" of snow, which I have to say is disappointing after looking at the radar this morning (see previous post).  After 7 am, storm totals were only .47" water and 6 inches of snow.  I thought we'd see something closer to 9-12 based on the morning radar.

Backcountry ski conditions ranged for very good to "pinbally".  Conditions were very good up high where the bottom was smooth.  Down low, in areas where there was overnight rain on snow (or at least a melt freeze cycle), we did a lot of bouncing off of old tracks.  Higher snowfall rates would have helped, but freshies are freshies.

I Love It When a Storm Comes Together!

From late yesterday afternoon until 7 AM this morning, Alta-Collins has observed 1.09" of water equivalent and Snowbasin Middle Bowl 1.15".  Ben Lomond Peak is around 1.4".

Temperatures at Alta-Collins (9662 ft) peaked at 32ºF from 11PM to midnight, afterwhich they lowered gradually and then more abruptly with the passage of the cold front early this morning.

At the base of Alta (8560 ft), and at Snowbasin Middle Bowl (7402 ft) it reached 37º.  Thus, rain may have mixed in with snow as high as the lower slopes of Alta and Snowbird and mid mountain Snowbasin during the warmest part of the storm around midnight.  Temperatures have since fallen and the recent passage of the cold front has lowered snow levels to the valley floor.

At upper elevations, the 1.09" of water at Alta-Collins yielded a total of 6" of snow, yielding a water content of 18%.  Serious Sierra Cement.  However, the snow falling this morning and today should be drier.

The radar loop is one that makes me really happy because it means snow for all elevations today.

There's nothing like a combination of atmospheric river moisture and frontal dynamics to give a solid band of precipitation.  Better yet that it will be moving slowly through northern Utah.  Thus, I'll stick with my storm total precipitation (1.5-2.25") and snowfall (12-20") forecast for Alta through 5 PM, but will note that the cards are stacked for totals in the upper half of those ranges.

I love it when a storm comes together!