Wasatch Weather Weenies

I keep hoping for a big storm cycle to add to the current snowpack, but the forecast is pessimistic.  Below is our experimental downscaled forecast system (see Snow is Coming but How Much for more information) and through 0000 UTC 7 December the downscaled average precipitation produced by the 22 ensemble forecasts is less than an inch of water for the central Wasatch and less than 12 inches of snow.  Only 80% of the downscaled ensemble forecasts produce more than 6 inches of snow in the higher elevations of the central Wasatch and none produce more than 24". Although I emphasize that this is an experimental product and we don't know the biases all that well (I suspect if anything these forecasts are too wet and snowy on average), it is sufficient to illustrate that we'll be living on storm scraps for the next week, with our best chance of snow late Tuesday and Wednesday.  Let's hope one of the snowier ( > 12 inch) forecasts verifies, although I suspect a more ...

I can't decide if cirrostratus or fog is my least favorite cloud, but after three days of high overcast and flat light, I'm leaning toward the former. Here's how things looked on Thanksgiving.  And here's how things looked today. Yup, cirrus monotony.  Come on Mother Nature, do something already!  Give us snow or give us sun! An irony of thick cirrostratus is that it produces flat light and difficult skiing, but it also results in outstanding visibility.  In fact, the best visibility is usually on days with high overcast.  This is because cirrus clouds reflect some of the incident sunlight back to space, so there's less scattering of sunlight by atmospheric gases and aerosols at low levels.  Below is the view from the Avenues foothills yesterday.  One can easily see Mt. Nebo, roughly 100 km distant, on the horizon to the right of the central Wasatch.

The Wasatch are a remarkably snowy interior mountain range, but they would be even snowier if not for the High Sierra. One way to illustrate this is to look at the fraction of cool-season (November to April) precipitation produced over the western U.S. when atmospheric rivers (ARs) are present.  ARs are filaments of strong water vapor transport characterized by high water vapor content and strong winds.  As can be seen in the figures below, more than half the cool-season precipitation along much of the U.S. west coast is produced when ARs are present.  ARs sometimes extend inland, especially over the Columbia Basin and panhandle of Idaho, the Snake River Plain and southwest central Idaho Mountains, and much of Arizona, where >30% of the cool-season precipitation occurs when ARs are present.  In contrast, AR penetration into central Nevada and Utah is less common and AR-related precipitation is less common. Source: Rutz et al. (2014) This is primarily the r...

Ideal weather will prevail over Utah tomorrow for your Thanksgiving festivities with high pressure firmly in control. I can think of only a few individuals who might be unhappy. Source: visualparadox.com Happy Thanksgiving!

The radar loop for this morning shows some very weak echoes forming over and upstream of the Wasatch Mountains.  If you look specifically at the eastern Salt Lake Valley, you'd probably think it is raining or snowing. Very little of that precipitation, however, is reaching the valley floor (although it's beginning to get close as I write this).  It's mostly snow that is falling and sublimating (when ice turns directly into vapor) before it reaches the ground. The reason that this precipitation shows up on radar is that the beam originates on a mountain peak (Promontory Point) and is oriented with a slight tilt relative to the horizon (0.5º).  The starting elevation, combined with the slight tilt and curvature of the Earth, overwhelms the slight tendency of the atmosphere to bend the beam back towards the Earth's surface.   As a result, the KMTX radar samples the atmosphere well above the valley floor, meaning it sees the snow aloft rather than what's happenin...

“ It doesn’t need a reason to snow in Little Cottonwood Canyon; it needs a reason to stop .”  - Alta Meteorologist Mike Kok The natural advantages of upper Little Cottonwood Canyon and the high terrain surrounding the Cottonwoods are on display today.  It doesn't look like much, but notice the weak radar reflectivities that have been lingering in the central Wasatch this afternoon.  Alta and upper Little Cottonwood Canyon identified with a red box. Those weak radar returns have been producing about an inch an hour of low-density fluff at the Alta-Collins site this afternoon.   Most of that snow growth is probably occurring at very low levels, some of it below the radar beam.  This is often a problem in shallow orographic storms, as illustrated conceptually in the figure below from my book Secrets of the Greatest Snow on Earth. Source: Secrets of the Greatest Snow on Earth If you look carefully at the radar loop above, you can see ano...

Pretty good storm totals in the upper Cottonwoods so far (as of 8 am) including 20 inches at our site in upper Albion Basin and 19 inches at Alta-Collins.  Water totals are also great for base building with 1.96 inches of water equivalent at the former and 2.21 inches at the latter.  That works out to a water content of about 10-12%, which is high by Utah standards, but it's stacked right and should ski great this morning, although there's lots of buried monsters (stumps rocks, etc.) and high backcountry avalanche danger to contend with.  Let's be careful out there! This morning we've had a nice round of orographic snowfall add to the totals, with some possible lake enhancement to the southeast of the Great Salt Lake.  This particular period of snowfall appears to be winding down as I write this (about 8:30 am).  If you look carefully at the radar loop, you can see one of the reasons why Park City gets so much less precipitation than the upper Cottonwoods. ...

Not much change from yesterday in the forecast for today and tonight (compare time-height section below with that in the previous post).  Looks like a pretty good dump for the Wasatch.  I suspect most of you will be happy in the morning.   I'm still perplexed about what to expect thereafter. It's the weekend, so I'll let you surf around and look a the divergent forecasts out there and pick what you want. A quick update on my book Secrets of the Greatest Snow on Earth.  Amazon is finally reporting that it will be in stock on November 25.  I've heard delivery dates ranging from November 28th to 30th.  Thanks for your patience!  In addition, it is now available in Nook and paperback (shipping with 24 hours) from Barnes and Noble .  I'm a huge fan of e-books, but in this case, I recommend the paperback.  For those of you on or near the University of Utah campus, I will be doing a lecture and book signing (Thanks to King's English who should ...

Time-height sections are remarkably powerful tools for weather forecasting (see Forecast Tools: The Time-Height Section for a basic introduction).  The forecast NAM time-height section for Salt Lake City for the next couple of days is an absolute classic, showing beautifully the likely storm environment changes over northern Utah. With time-height sections, we typically reverse the x-axis so that time increases to the left, as is the case above.  So, scan from right to left to see the passage of various weather systems between now and Monday afternoon.  Instead of temperature, we also use a thermodynamic variable known as equivalent potential temperature, also known as theta-e or  θe,  which considers temperature and moisture and can be useful for examining atmospheric stability. As can be seen above, we begin today with a mainly dry (and polluted environment).  The leading edge of the precipitation system is marked by a pronounced warm front ...

I've been distracted by Buffalo's snowmaggedon the past couple of days.  Incredibly, they are getting more again today.  Never has so much powder gone to waste.  If only Mother Nature could have arranged for the Adirondacks, especially the high peaks , to be located more strategically relative to Lakes Erie and Ontario. Of course, there is a place where Mother Nature has fortuitously aligned the weather, topography, and geography for great skiing and that's the Cottonwood Canyons.  And, the good news is that we are going to be getting some beginning this weekend.  The storm will be warm on Saturday with a passing warm front.  Following the cold frontal passage late Saturday, temperatures will fall and we are looking at what will likely be an active northwesterly flow period through Monday Night and possibly Tuesday. The image below shows the 1200 UTC GFS forecast accumulated water-equivalent precipitation through 0000 UTC 25 Nov (6 PM Monday MST). ...

Do you ever wonder what it would be like if it started snowing and never stopped? - Steve Casimiro, Editor, Powder Magazine, 1987-1998 The quote above is one of my favorites and one that I often think of during major snow events.  It came to mind this morning as I examined the snowfall totals for the Buffalo area so far, with maximum storm-total accumulations of more than 60 inches.   At the moment, it's actually not snowing in Buffalo.  The camera image below shows the New York State Thruway near West Seneca, near the heart of the most intense snowfall.  This is a major thoroughfare and one of the best maintained highways in America.  They have finally carved a trough through the snow, but there's a lot of work still to do.   A few miles to the north accumulations are much lower and the road looks fine.   Although Buffalo can exhale this morning, more snow is expected later today, tonight, and tomorrow.   At first, ...

Note: This post has been updated to include a remarkable video of the lake-effect band at the end.  You don't see this every day.  Even in metric, 40-60 (cm) is a pretty good storm.  But this is the forecast in inches.  Source: WIVB.com Contrary to popular belief, Buffalo is not the snowiest city in the United States, it's Syracuse (96 vs. 126 inches).  However, when it comes to behemoth storms, Buffalo is king.  Why?  It sits on the eastern end of highly elongated Lake Erie and thus can be pounded by intense snowbands that form along the major lake axis.  Such snowbands are sometimes called Long-Lake Axis Parallel or LLAP bands and are responsible for some of the most intense snowstorms in the world.  Last night and today portions of the Buffalo Metro Area have been getting pounded by a persistent LLAP band, as illustrated by the 18-hour-long radar loop below.  The approximate position of the Buffalo metro area is outline by the...

I've been told by some of you that you've received e-mails from Amazon stating that they are having trouble obtaining copies of Secrets of the Greatest Snow on Earth.  I'm not sure what the problem is with their cyborgs but I suspect that there's been some minor glitch in their receipt or processing that's pushed their ship date past November 14.  Sit tight as I suspect it won't be long now. I do know that copies are available currently at Weller Book Works in Trolley Square.  You can find them on their signed copies table and in their winter sports section.  You should also be able to order directly from Utah State University Press  or by calling their customer service center at 1-800-621-2736.  I just bought 20 copies and they will be here by the end of the week.  Alternatively, check with your favorite book store as the book is beginning to appear at other retailers.   Thanks for the interest and patience!

I know everyone is anxiously waiting for more snow, but it's worth remembering that even though the odds are better here than elsewhere, it's still pretty much a crap shoot for having a decent natural snowpack by mid November. Let's take a look, for example, at the snowpack statistics at the Snowbird SNOTEL site, which covers a 26-year period.  The snowpack snow water content at this site currently sits at 2.4 inches, compared to a median of 4.0 inches (and an average that is also right around 4 inches).  That basically means that the difference between what we have right now and average is one good storm (think a wet 15 incher).  Years with big snowpacks in early to mid-November, like 2004-2005 (purple) are really fantastic, but they are the exception, not the rule.  What we have right now is not all that unusual. When I moved to Utah, I was always surprised to see snow rich resorts like Alta making snow.  It seemed like an embarrassment of riches, but i...

Thanks to a few hours of low-density snowfall this morning, the overnight and morning totals in upper Little Cottonwood aren't looking too bad. Automated interval board observations at the Collins site show the 3 inches that fell Thursday night.  The board was wiped between the 1600 MST and 1700 MST observation, then you can see the accumulation of about 10 inches of snow through 0900 MST this morning (ignore the spurious 34 inch observation at 0600 - one of the hazards of automated snow measurements are the occasional spurious observations).  It appears the board was wiped this morning between 0900 and 1000 MST with a 3 inch accumulation after the wiping.  That observation seemed a little odd given that only .01" was observed by the rain gauge.  If it is legit, that would give us an event total of 16 inches and an overnight total of 13 inches.  If not, it's more like 13 and 10. I believe that Collins Gulch is currently closed to uphill skiing.  If y...

Imagine if Jack Bauer wasn't a secret agent, but instead was a meteorologist.  Fox would have an endless treasure trove of plot ideas to tap into.  Forecasts for severe and unusual weather.  Tornado out breaks.  Snowstorms.   Let's start season 1 this morning since the next 24 hours are pretty interesting. Instead of terrorists, we have a band of precipitation precipitation near the Utah–Idaho border.  There are a few scattered showers over the Wasatch Range to the south.  This pattern will likely persist for most of the day today.  The north gets most of the action, while we get some intermittent mountain snow showers to the south.  It's not too exciting, but the climax is of course tonight. The NAM forecast for 0300 UTC (2000 MST) shows things picking up in the evening.  The main precipitation band associated with the approaching front remains to the north, but the orographic snow showers pick should be picking up in frequenc...

With regards to the forecast through the weekend, we're in a tough spot.  The pattern in the higher latitudes is completely wacked out with a high-amplitude ridge centered currently over the Yukon Terrritory and a deep trough over the eastern United States.  Meanwhile, southerly flow is cutting underneath the high-amplitude ridge and penetrating over the southwest U.S. Downstream of the col in the height pattern, Utah is in an area of confluence between westerly flow from over the Pacific and flow originating over western Canada, as illustrated above.   In terms of the timing and intensity of precipitation features moving through northern Utah, there's a lot of sensitivity in a pattern like this and I've been watching the models struggle coming to a consensus over the past couple of days.  Look at the difference, for example, in the GFS (top) and NAM (bottom) forecasts for 11 PM MST Saturday night.  The GFS has the upper-level trough axis over northern Utah...

My first interview about Secrets of the Greatest Snow on Earth occurred this morning on Utah Public Radio.  Click here for a listen.

The new High Resolution Rapid Refresh (HRRR) modeling system is now providing remarkably detailed analyses and short-range (0-15 hour) forecasts operationally at 3-km grid spacing.  This is a major advance for weather analysis and forecasting in the United States and I'm hoping it should prove useful for ski forecasting this winter. Below is the HRRR analysis for 1300 UTC (0600 MST) this morning showing the remarkable structure of the current cold surge interaction with the high topography near and along the Continental Divide.  Analyzed surface temperatures are below -12ºF across much of central Wyoming and southwest Montana.  The strong pressure gradient associated with this cold airmass is driving easterly and northeasterly flow into the Columbia Basin, Snake River Plain, and northern Utah.  In the case of the latter, one can see how the Uinta Mountains splits the cold flow, with easterlies pushing across Evanston to the Wasatch Mountains and northeasterlies pus...