Wasatch Weather Weenies

For those of you who like to get your weather geek on, I've begun to populate weather.utah.edu with some new products, specifically full vertical resolution model soundings from select locations in Utah and a few other sites of interest.  Here's an example from the NAM for 2100 UTC (3 PM MDT) this afternoon. These soundings are really fantastic and should be helpful for forecasting.  For the NAM, they are available every hour, which will be great for periods of rapid change.  If you want to see a loop of the hourly soundings, click here . I'm hoping to have these for the GFS as well, although they have lower vertical and temporal resolution and thus won't be as sharp or useful. The old soundings will be deleted as I need to cut some CPU time from somewhere!

This winter, NCEP upgraded the Global Forecast System (GFS), with improvements in both resolution and physics.  While it is likely improved forecasts of fronts, cyclones, and other major weather systems the precipitation forecasts over the central Wasatch are simply abysmal. I noticed something was up immediately following the upgrade.  NCEP began to provide direct model output (known as BUFR) for the model grid point closest to Alta.  I began downloading and plotting this data [see http://weather.utah.edu/text/COTTONWOODS.txt (GFS at bottom) and  http://weather.utah.edu/index.php?t=gfs004&r=ALTA&d=MG ] and noticed immediately that the GFS was generating far too much precipitation. I then began downloading the native (13-km) resolution GFS grid from NCEP and examining the precipitation, which showed extreme amounts of precipitation over many mountain areas.  Here's an example from 23 January through 22 Feb (courtesy of a colleague).  During...

My friends at UDOT tell me that Alta-Guard sits at 276.8" of snowfall for Nov–Apr.  The previous low was 314.5" in 1976/77. With nothing but a flurry or two possible through the end of the month, the record is in the bag.  Congratulations, you survived the lowest snowfall season since WWII, although I still rate 1976/77 as a worse ski season (see Has There Ever Been a Snow Season Like This? ). Of course, the usual caveats apply (see Limitations of Long-Term Snowfall Records ).

There was some good upper-elevation snow to be had today, but visibility was about as nasty as it can get in the Wasatch.  I opted for a tour in the Supreme area and was glad I did as the trees were essential.  Conditions were quite good above about 9500 feet. I returned to Alta only to discover that I had actually been transported to the Cascades.  That's the Albion and Sunnyside lifts from the Albion Grill.  Visibility perhaps 150 meters. The high humidity air made for some nice hoar frost on my son's hair.  Not sure if the vapor source was the atmosphere or his perspiration.  He is a teenager after all.

The skiing wasn't half bad this morning as the cream-on-crust skied pretty well despite the fact that it only added up to about 7 inches in the upper elevations and far less in the lower elevations.  It was nice to see white snow again, although the snirt was very quickly starting to appear in tracked areas by noon. I've lived long enough in Utah to know that we can get some freshies nearly any time of year and I've seen some good dumps in May and even early June.  Even if that happens this year, the snow we get tonight will be, for all intents and purposes, the last dump of the season.   I suspect that something in the 4-8 inch range is the most likely scenario for accumulations in upper Little Cottonwood through 9 am tomorrow, with a modest chance we'll do better than that.  With an early start, the high altitude (>9500-10000 ft) north aspect ski touring might be decent tomorrow as the snow should be right-side up and falling on what we got last night. ...

Snow remains in the forecast and hopefully we'll have some white stuff this weekend for Alta's closing day #2, to help Snowbird extend their season, and perhaps to give us an extra week or so of white corn in the backcountry.  However, I have something more entertaining to share than a discussion of the weekend forecast. Jeff Lukas is a research scientist with the Western Water Assessment .  He recently presented a Dr. Seuss inspired summary of recent and future climate and water trends for Colorado that has gone viral amongst my colleagues.  It's worth a 5 minute look and does an excellent job summarizing current knowledge of our changing hydroclimate. Although emphasizing Colorado and the recently completed report, Climate Change in Colorado , it is quite applicable to Utah.  

I had what I thought was a great last ski day of the year last weekend.  With warm weather on tap for this week and a layer of dusty snow not buried far below the surface, I figured that we'd be skiing nothing but snirt by this weekend. I'm now thinking that I will be doing some skiing this weekend.  The models are advertising the passage of two troughs, the first late Friday and the second late Saturday. These look to be fairly warm systems bringing mountain snow and valley rain through Saturday, with somewhat cooler air moving in for Sunday, although even then current forecasts suggest snow levels at or above bench level.  Given the warmth of the storm, expect heavy, near-Cascadian snow that may become somewhat drier on Sunday. Nevertheless it's white.  Our downscaled ensemble forecast plumes show the two periods of heavier precipitation with a mean water equivalent after subtracting off the showery stuff today and early tomorrow of about 1.5 inches w...

"Good intentions score big, good actions score bigger" –Mark Fischetti, Scientific American Yesterday, in honor of Earth Day, I did something I've been dying to do for some time. I told Commuter Services to stick it ! Actually, that's an over statement.  I called them up and politely cancelled my parking pass.  Although Earth Day provided some motivation, the cancellation was the result of several factors, not all environmental.  Depending on your situation, you might be able to do it too.  Skip to item 4 if you don't want the back story. I've always been a multimode commuter.  For many years this involved biking in the summers and driving in the winters.  I was never a bus fan primarily because I found it so inconvenient, but circumstances have changed and the bus has become my primary mode of commuting.  Here's why. 1. The development of smart phones and bus-tracking apps .  I no longer waste time at the bus stop.  I get ready...

A somewhat smoky/dusty sunrise of the Salt Lake Valley this morning Several days ago, wildfires set by Russian farmers in preparation of spring planting raged out of control, killing 23 and leaving more than 5,000 homeless .  It was a terrible catastrophe. Smoke from these fires, along with perhaps some Asian dust, has since spread across the Pacific. Source: NASA And is currently draped across portions of the western U.S.  Below is an image from MODIS from yesterday.  The smoke is easiest to see against the dark background of Pacific Northwest fires west of the Cascade Crest.   Here's an image showing the estimated aerosol optical depth.   Warmer colors indicate higher aerosol concentrations.   Evidence of the smoke can also be seen in air quality observations, which show a gradual upward trend in PM2.5 over the past two days.

It was the first closing day of the season at Alta today.  Although the freshies are gone, the turns were quite good and you could carve a hell of a trench for much of the afternoon. As usual, costumes and revelry prevailed for the day. Special thanks to this dude for throwing in some old-school air and for keeping his clothes on. Snirty snow is already making an appearance in wind scoured and sun exposed areas.  A brown spring is in our future. There was something in the air throughout the day obscuring the views.  I was wondering if it was smoke from the Siberian fires.  Perhaps one of you out there can take a look and comment. Now is a good time to say thanks to all the avy pros, patrollers, snowmakers, groomers, and lifties for their exceptional efforts this difficult snow year.

"A very strong cold front arrived on April 15th with near hurricane velocity winds.  The storm knocked down trees, signs and power poles all over Utah and filled the air with choking dust.  In the next week, 42 inches of snow fell on top of the chocolate brown layer of dust.  Backcountry recreationists had their last fling with some of the best powder of the season on mostly stable snow.  Then, finally, spring arrived." Sound familiar?  That quote is from the Utah Avalanche Center 2001-2002 annual report.  The very strong cold front on April 15th was produced by the 2002 Tax Day Storm, which like the storm we experienced earlier this week, was a huge dust producer. AVHRR satellite imagery at 2046 UTC 15 April 2002.  Dusty areas not obscured by clouds identified with warm colors in inset at upper left.  Source: West and Steenburgh (2010) . The snow that year was remarkably brown once we were well into the melt season.  We are guarantee...

As Mr. Rodgers liked to say, it's a beautiful day in the neighborhood!  It feels so good to have a taste of winter, even if it is in April.  Snow totals in the mountains are crazy big in Little Cottonwood. Snowbird has a 45 inch storm total, Alta-Collins 32 inches based on the automated sensor.  As discussed in the previous post,  Snowbird Dumpage , the biggest snow totals appear to be in mid Little Cottonwood and  drop off as one moves through Twin Lakes Pass into upper Big Cottonwood and then even more dramatically as one moves further east to Park City.  As meteorologist and backcountry skier S. D. Green said in 1935, " Skiers will eventually find that the…heads of the [Cottonwood] canyons…offer the best skiing to be found in the Wasatch Mountains."   That dude knew his weather. On Monday, a friend in the avalanche business told me that he was hoping we would obliterate the all-time low snow season at Alta-Guard.  We have suffered mightily...

This afternoon, some great micrometeorological magic has been blessing Snowbird, which is now reporting 36" of new snow.  Snowfall amounts appear to decrease as one moves further east.  Automated sensors at Alta-Collins show 24" and near the base of Supreme 17".  I've also heard reports of lesser amounts from ski tourers at Solitude, and of lesser amounts at the top of the Tram compared to lower on the mountain at Snowbird.   I'm always hesitant to jump to conclusions based on automated sensors, so this discussion should be read with caution.  Nevertheless, the radar seems to support the view of a decline in snowfall from Little Cottonwood to Big Cottonwood to Park City.  Although this often occurs in NW flow, it's appears to be especially pronounced this afternoon.  To show this, I'll show a radar loop in which the high terrain around Little Cottonwood and the Park City ridge line are identifed with red lines.   In the loop below, wh...

Tuesday Afternoon to Wednesday Morning: Change You Can Believe In! What a storm!  Massive temperature fall, high winds, blowing dust, and now heavy snow.  It's a meteorological dream!  What do we call it?  The Black Tuesday/White Wednesday Storm?  The Tax Day II Storm?  Make suggestions.  Naming rights will be auctioned off later today. Let's look at this storm piece by piece. Temperatures We'll concentrate here on the University of Utah because we have a long record of 5-minute temperatures allowing for comparison with earlier storms.  At the University of Utah, yesterday's maximum temperature was 71ºF, achieved just before frontal passage, which occurred between 2:45 and 2:50 PM MDT. The temperature changes accompanying the frontal passage include 12.4F in 5 min, 17.8F in 10 min, 21.1F in 1 h, and 29F in 2 h.  The total temperature change from 71F at 2:30 to 32F at 8:05 was 39F. The mother of all Salt Lake City front...

A remarkable dust storm has been raging over the Salt Lake Valley now for a few hours.  As is often the case, the dust became very concentrated along the cold front, resulting in what I'll call Black Storm conditions.  The Black Storm is a name commonly used for intense dust storms over China. Evidence for the extreme nature of the dust is provided by visibilities at the Salt Lake City International Airport, which dropped to a half mile immediately following frontal passage.  In addition, observations at the University of Utah show a nearly instantaneous temperature fall from 70ºF to 52ºF with a concurrent PM2.5 spike to over 210 ug/m3.  For reference, the clean-air act standard is 35 ug/m3 (24-hour average). I've been sheltering inside, but I'm sure the frontal passage was positively miserable to experience outside.

I love days like this.  A quick update. As anticipated, the new front has formed over eastern Nevada and Northwest Utah and is now draped across the Salt Flats and northern Great Salt Lake. This is clearly a case of discrete propagation.  Despite the NW wind, it is currently 63ºF at Wendover.  That's much warmer than what was immediately behind the front 24 hours ago. Remarkable dust plumes are being driven by the strong southerlies ahead of the front.  These plumes can be clearly seen in visible satellite imagery (not to mention by looking out the window). Major dust sources below are outlined in red boxes and include the West Desert in and around Dugway Proving Ground, the Tule Valley (I think there's a small dry lake bed there), and the Sevier Lake Bed.   There are probably others. Visibility in the Salt Lake Valley is dropping like a rock.  We are seeing PM2.5 concentrations on our Trax mounted sensor in excess of 20 ug/m3.  Air quali...

I hope you brought a jacket to work or school today as you are going to need it later this afternoon. Yesterday we discussed the anticipated discrete propagation of a cold front across the Intermountain West (see Excitement At Last! ).  Everything is coming together this morning for this to occur and for a strong cold front to move through the Salt Lake Valley later today. We begin with a trick question.  Where is the front in the image below? That band of precipitation in central Nevada really gets my attention, as does the shift in the wind from southerly at Elko to Northwesterly at Winnemucca.  Compared to balmy Salt Lake City, it's another world right now in Winnemucca (when isn't it — ha ha) with a temperature of 36ºF and a NW wind of 20 knots. However, let me add the corresponding short-range HRRR forecast of 700-mb temperature and wind to that plot.  When I do this, you can see that indeed there is a trough associated with that band of precipitation...

Tuesday and Wednesday look to be the most meteorologically exciting period we've had around here in some time as a strong cold front develops over the Intermountain West.  There's something for everyone including strong winds, blowing dust, mountain snow, and then, for Tuesday night and Wednesday morning, the chance of mountain and valley snow depending on how everything comes together.  The forecast for 1800 UTC (1200 MDT) today shows a Pacific cold front making landfall along the Pacific Northwest coast.  Ahead of the landfalling cold front, however, temperatures increase fairly dramatically from the Pacific coast to the Intermountain West (circled). As the Pacific cold front pushes into the interior, a new cold front forms ahead of it from that temperature gradient that currently exists from the Pacific coast to the Intermountain West.  By the time we get to 2100 UTC (1500 MDT) tomorrow, the front pushing through Utah is essentially a new front, with th...