Wasatch Weather Weenies

There are a lot of ways to look at the downscaled NAEFS plume for Alta-Collins below.  One could focus on the upper-end forecasts.  What could be better than 5+ inches of water and 75+ inches of snow?   Or one could look at the low end forecasts.  Those aren't so bad, but give a pretty different result with less than 20 inches of snow and 1.5 inches of water.   Or one could see the period beginning on Friday morning (about 12Z 1 Dec) through Monday (about 18Z 4 December) as a stormy period in which there are a wide range of possibilities depending on details that cannot be confidently predicted at this stage.   Let's take a look at what some of the models are saying.  The GFS is pretty much right in the mean of the NAEFS forecast and puts out a total of 2.75" of water and 41.8" of snow for Alta-Collins.  A close look at the accumulated precipitation and snowfall traces shows a series of three waves moving through, with precipitation...

It's pretty rare that stratus clouds, which otherwise are a zero on a meteorological scale of 1 to 10, can make for a great weather day, but they did today.   Morning dawned in the Salt Lake Valley with dreary, grey overcast in the form of stratus clouds covering the entire sky (the image below taken looking south from the U at 8:12 AM).  However, a look toward the Cottonwoods showed a brighter spot, suggesting that perhaps there was hope for sun at high elevations.   Source: University of Utah Department of Atmospheric Sciences Sure enough, the Alta webcam showed clear skies above a Sea of Stratus over the Salt Lake Valley.   Source: Alta Ski Area And the morning satellite loop was really quite incredible with snow capped mountains, especially the central Wasatch, Southern Wasatch, and Uinta Mountains, sticking up above the Stratus Sea.   Source: College of DuPage And, as we started out ski tour from Alta at 9:52 AM, skies were clear, althou...

Instead of arguing with your crazy uncle about politics this Thanksgiving, consider arguing about the weather instead.  There's certainly plenty of room for debate and disagreement if you are trying to forecast snowfall in northern Utah.   The culprit is an upper-level trough that will develop and "dig" (move equatorward) over the Great Basin on Thanksgiving.  at 1200 UTC 23 November (5 AM MST Thanksgiving morning), the trough is forecast to be an open wave  with no closed circulation and an axis that extends from Oregon and California.  However, the trough is also diffluent , with an intense jet on it's upstream side and flow that weakens and fans out on its downstream side.  Such troughs are prone to amplification and digging, and that is exactly what is forecast to happen during the day on Thanksgiving.  By 0000 UTC 22 November (5 PM MST Thanksgiving), the trough has closed off over southern Idaho, and concomitant precipitation is moving into n...

Pretty good weekend storm if you happen to be in the hallowed ground that is Little Cottonwood Canyon.  Based on the automated measurements, Alta-Collins got 5 inches of snow on Saturday (with .51" of water), far more than I was expecting (which would have been maybe an inch or two) to get the weekend off right.  Then another 14" with 1.54" of water on Sunday, bringing the storm total to 19".   Watching the radar yesterday, it was very apparent that the economics of this storm was going to increase the snowfall wealth divide.  Given the northwesterly flow and shallow nature of the storm, echoes tended to be stronger and more persistent over the Salt Lake Valley, lower to middle Big Cottonwood Canyon, and Little Cottonwood Canyon than over the Park City Ridgeline (red line below) or south and east of the Alpine Divide between Little Cottonwood and American Fork Canyon (purple line), as shown in the example below.   Thus, Alta and Snowbird, which flank M...

Change is coming, albeit a temporary one, in the form of a digging trough that will bring a pretty good round of snow to the Wasatch on Sunday. Until then, today (Saturday) will be a "meh" day with a few upper elevations now showers in the form of wet snow up high and rain below about 7500 or 8000 feet.   But Sunday looks better.  The GFS forecast valid 1200 UTC 19 October (5 AM Sunday) shows the trough extending from the Washington coast into western Nevada with precipitation spreading eastward to northern Utah.   During the day Sunday, we should get an extended period of mountain snowfall with the frontal passage and eventually, as pictured below, the cold northwesterly flow during the afternoon.   This is not a prolonged storm cycle with multiple waves to really help build snowpack.  Snowfall will begin Sunday morning and probably taper off shortly after 11 PM.  The 6Z GFS is putting out a total (including the dribs and drabs today) of abo...

Sort of a "mixed-bag" storm last night and this morning with some good and bad news. The good news is that we got the precipitation that the models were advertising to develop.  The bad news is it was even warmer than advertised a day or two ago, with relatively high snow levels, at least for the overnight and early morning precipitation period.  Automated observations from Alta-Collins show 0.81" of precipitation, which would be in the upper end of forecasts from a couple of days ago.  The bad news is that temperatures at Alta–Collins during the precipitation period were 34˚F to start and are currently sitting at 32˚F, so this was gloppy, wet snow adding up to only 3 inches.   It may have even started as mixed rain and snow at that elevation (9662 ft).  Above that elevation, there's probably a pasting of high density snow.   Below that elevation, it was even warmer at the base of Alta, which as of 7 AM was 35˚F.  As of 7:45 AM, the Mt. Super...

For the past several days, some of our computer models have been producing a somewhat unusual banded precipitation event for northern Utah on Thursday.  I'm not sure what to make of it, but let's take a look.   We'll begin with the setup.  Below is the GFS forecast for 1200 UTC 15 November (5 AM MDT Wednesday).   The upper-level flow off the Pacific coast is best described as "split" with a branch of the jet south of a deep low off the coast of California and a second branch over the Pacific Northwest.  The latter has a short-wave trough embedded in it (sashed line).  Over the Pacific Northwest, those two branches come together.  This is referred to as confluence by meteorologists.   By 0600 UTC 16 November (11 PM MST Wednesday), the upper-level trough in the northern branch of the jet has moved over Idaho and a second trough that is pinwheeling around the low has is over the Sierra Nevada.  The confluent flow has shifted down...

Update from Jim @6PM :  Due to an issue on our server, the NAEFS forecast used below is old.  Updated forecasts still show scant precipitation until the 16th.  Let's hope things look better after that. ---- Wait and see is the summary of the forecast today.   Snow conditions on the "Collins Glacier" improved marginally this past week thanks largely to artificial snow which helped improve the cover a bit, although there are many areas even along the main line where the snowpack remains scant.  The view from Germania Pass pretty much tells the story and shows why Alta is hesitant to open.  There's still a lot of work to do before they have adequate top-to-bottom coverage on even a single run.  The coverage is probably best in the high collection areas up high (Ballroom, Baldy Shoulder), at least in those areas that are not littered with big rocks, and ironically near the base where they have made a good deal of snow.  Still, it's low-tide condi...

The start of ski season is always a bit of a crap shoot, even in Little Cottonwood Canyon.  Sometimes we get started in October.  Other times it can be deep into November.  What can be skied varies. Two of the more memorable starts were in the early 2000s.  In 2001, snow was scant and the resorts were not open on Thanksgiving.  Then Alta got 100 inches in 100 hours during the holiday weekend and it was on.      In October 2005 2004 (Editor: My bad!), we got pounded and Brighton was open not by Thanksgiving but Halloween.   This year Mother Nature is electing to tease us with infrequent storms of modest size.  Per the Alta web site, 13.5" on October 11 and 12,  7.5" on October 26, and 11" on November 7.  Storm size and frequency have both been too small to establish a snowpack on sunny aspects, while a very marginal snow depth of 15" lingers at the Alta-Collins observing site.  Snow depth and water equivalent at the S...

I'd like to share a few updates that we've made to products on weather.utah.edu since last winter.  The Little Cottonwood forecast guidance derived from the HRRR ( https://www.inscc.utah.edu/~steenburgh/ml/hrrrlccforecast.html ) and GFS ( https://www.inscc.utah.edu/~steenburgh/ml/gfslccforecast.html ) has been updated with retrained machine learning algorithms that include last season in the training dataset.  An example from the GFS is below.   We also added a temperature forecast for the Collins (9662 ft) observing site, which is a bit more representative of mid-mountain conditions than Mt. Baldy, which is still included as it is useful for ridge-top temperatures. The new snow-to-liquid ratio (SLR) algorithm is based on a technique known as a random forest trained with observations from Alta-Collins.  It is more accurate and should produce a somewhat wider range of SLRs (up to about 25:1 if conditions are right) than the technique we used last year.  We t...

If anybody is looking for a cheap bike, I'm selling my 2008 Cannondale Rush 26er for $200.  Full suspension (100 mm travel) carbon fiber frame (medium).  Lefty shock (the one item that has relatively low mileage as it is the 3rd one I had on this bike.  Tubeless. Teeth on the rear cassette and front chainrings are worn down to nubbins.   It was once a great bike, but has been lapped by new geometry.  Would work if you are looking for a Lefty shock, commuter bike, or maybe to get your kid into riding at low cost. I've been riding a different bike for a couple of years and need to get this one out of the garage.   If interested, e-mail me at jim.steenburgh at gmail dot com.  

I got out for a few turns of the year today on the "Collins Glacier."  Like most glaciers around the world, it's not in good shape right now.  Oddly, the coverage and skiing are probably best on the lower half where humans have decided to help.   The snow there is firm but generally carveable, at least in the early afternoon when there's been some sun on it.   The man-made coverage continues to lower Mambo. There is, however, a gap in coverage just above the angle station that seemed to be growing in size in today's sun.   It gets grim in places with sun exposure.   Coverage improves again in Ballroom and environs, although the snow conditions there were challenging, especially for the first turns of the year.  There are also some Great White Sharks looming in places, just waiting to take a bite out of your skis.   We need snow.  Next shot is on Tuesday, although there's a great deal of spread in how productive that s...

October is in the bag.  I would describe it as fairly meh with nothing too extreme.   At the Salt Lake City International Airport the average temperature was 55.9˚F.  This was warm, but not exceptionally so, rating as the 24th warmest October since 1874.   Source: https://xmacis.rcc-acis.org/ The airport recorded 1.97" of precipitation.  A bit wet, but not exceptionally so, rating as the 36th wettest October since 1874.  Up at Alta, the cooperative site in town recorded 4.01" of water and 14.9" of snow.  The records for that site are fairly spotty so good long-term comparisons are difficult.  The ski area, which measures higher on the mountain, reported 22", compared to an average since 1980 of 26.6".   Essentially it was a Goldilocks October weather wise in northern Utah.   Utah has not had a statewide average annual temperature below the 20th century average since 1993.  Numbers through October are not ye...