Wasatch Weather Weenies

After five years of nearly continuous blogging, I am taking a break during the holidays this year.  Please check back in 2016.  My best wishes to you for deep powder and an enjoyable holiday season. If you enjoy this blog, please consider making a donation to our Mountain Meteorology Fund .  The fund supports research and education in mountain weather and climate at the University of Utah.  Visits by people like Jordy Hendrix were made possible this past year because of the fund, as well as support for students who make many of the custom and experimental products we provide on weather.utah.edu and which are used by many in the Wasatch forecast and ski communities.

Skiing today involved breaking trench up...and at times, down! After reading some reports of good low angle skiing yesterday, I was pumped for a ski tour today. In the wake of this morning's cold front, however, temperatures dropped and the winds picked up.  Peak gusts on the higher peaks exceeded 80 mph and snow was moving nearly everywhere, including at lower elevations. Basically it was a perfect recipe for an upside-down-cake snowpack with the high density wind affected snow sitting on top of a remarkably deep layer of lower density snow.  Conditions were about as difficulty as any I've skied in open areas.  My advice for tomorrow: Stick to the low angle trees in wind sheltered areas and hope for the best!

It's a hell of a storm and it is raging again this morning as a cold from moves through northern Utah making the morning commute miserable in the Salt Lake Valley, but also pushing accumulations in the mountains to even higher levels.  It should be a quick hitter for the valley, but the timing is bad news for anyone having to travel during the morning rush. Source: RAL As of this morning, water totals in the mountains are impressive.  Ben Lomond Peak's automated gauge is up to nearly 5 inches (green dots).  Snowbasin middle bowl is approaching 4.5 inches (blue line).  Alta-Collins is at 2.4 inches.  The big winner is Sundances site with over 6.5 inches, although the Utah Avalanche Center is reporting 4 inches in their advisory this morning, so I wonder if that might be overdone compared to manual observations.  It is apparent, however, that they got quite a pasting down there. Source: MesoWest With the total snow depth at Alta-Collins up...

It is unusual, but upper Little Cottonwood seems to be a dry spot in this storm, although dry spot in this sense is a relative term. Observations from Alta-Collins show a total of about 27 inches of snow if you add up all the interval accumulations before the board is wiped back down to zero (top panel) and include the 4 inches observed so far today.  The water total is only 1.6 inches, although there may be some underdone a bit as that yields a water content of only 6%, which seems quite low compared to other locations. Source: MesoWest In contrast, Snowbasin has had 3.4" of water, more than double that at Alta-Collins (note scale change). Source: MesoWest In addition, snowfall reports from upper Big Cottonwood and Deer Valley have also topped those in upper Little Cottonwood.  I'm less sure about PCMR, but suspect they are at least close to what Alta has had so far too.   And the latest radar shows that it continues to snow at Snowbasin, but Alta is tem...

We may be amateurs, but every now and then we pull the government weather-control levers and get it right.  Despite a brief lull yesterday evening that briefly caused many of my friends to text or e-mail me to ask if the storm was over (no, it wasn't), this storm has has provided Christmas presents for all you girls and boys. Let's start with some water totals since 5 AM yesterday from automated sensors that report to MesoWest: Northern Wasatch Ben Lomond Peak: 3.3" (through 6 am) Ben Lomond Trail: 2.1" (through 6 am) Snowbasin Middle Bowl: 2.35" (through 7:15 am) Central Wasatch Alta-Collins: 1.01" (through 7 am) I'm seeing some widely disparate SNOTEL measurements in the central and southern Wasatch depending on if the gauge or pillow measurement is used, so I'm not using them here.  Snow reports in Park City and Big Cottonwood Canyon, however, are much higher than those in Little Cottonwood Canyon, so it's safe to assume tha...

I love mornings like this as I anticipate an approaching storm and peer out of my office at a cap cloud draped over Lone Peak. We had a pretty good storm last week, but that was a cold storm producing low density cold smoke.  This week's storm promises to be of the juicier variety. This morning's 1200 UTC (0500 MST) analysis shows a potent atmospheric river, characterized by a tongue of high precipitable water (warm colors) extending from the sub-tropical west Pacific across the north Pacific. Atmospheric rivers typically decay rapidly as they move inland, so if you one to survive intact to Utah, it's best to start with a strong one on the coast and then to bring it inland through regions of low topography so that there's less water-vapor depletion over upstream mountain ranges.  Avoiding the southern high Sierra is essential, and the best option is to bring it across the comparatively low Sierra and Cascade crest of northern California and across northern N...

The Snow Miser has some tricks up his sleeve for Christmas Week After some periods of mountain snow Sunday and Monday, some serious winter weather will be blowing into the Wasatch late Monday and Tuesday.  As shown by the GFS forecast below, which is valid for 1800 UTC (1100 MST) Tuesday, the Pacific jet is expected to extend into the Intermountain West, yielding strong westerly and west-northwesterly flow at nearly all levels.  This is an extremely moist fetch as well, with strong orographic enhancement expected over the mountains. This can also be seen in the GFS time-height section for Salt Lake City (time increases to the left).  That period around 1800 UTC Sunday features deep moisture and very strong flow, reaching 50 knots as low as 750 mb (~8500 ft).   Our downscaled NAEFS forecast plumes show the light accumulations ahead of the storm, but then the big event on Tuesday (22 December) when most ensemble members are generating over 2 inches of...

Great banner cloud downstream of Mt. Baldy this morning. Classes at the U ended last week, but these motivated graduate students got a real-world education about Wasatch weather today. And what a sunset!

Clouds are quickly returning this morning over the Salt Lake Valley, but as is evident in the photo above, it was a bluebird sunrise that ignites a skier's soul this morning.  Winter has finally returned to northern Utah. Cold Smoke Although it took a little while to get going with the benches picking up more snow on Monday , the Little Cottonwood snowmaking machine has been going full bore since Monday night with another 12" falling overnight.  That brings their storm total to 46 inches of cold smoke.  The water content of that snow was only 1.9", yielding a mean water content of only 4.1%.  Thus, that 46" won't go as far as you think for base building, but have no fear, because more snow is coming.... A Snowy Future Readers of this blog know I don't like to hang my hat on detailed, specific, medium-range forecasts, but by and large, it looks pretty good that after a bit of a break through Saturday (other than perhaps some snow showers tonight), w...

It's been quite a while since we had a storm like this, especially on the valleys and benches.  It's great to have winter as it should be.  A few thoughts on the event this morning. How good were the forecasts? Snow forecasting in northern Utah is all about synoptic possibilities and mesoscale uncertainties.  The former means that we can often anticipate when the large-scale ingredients for a significant storm are present, but the latter implies that the devil is in the detail and specific forecasts of the timing, intensity, and spatial distribution of the snowfall is exceedingly difficult. For the present storm, we had strong agreement amongst the models and ensemble modeling systems that a significant storm would hit the state.  The NWS issued watches and warnings in a timely manner with good lead time.  The forecasts did not capture, however, some aspects of the snowfall timing, intensity, and distribution, most notably in some bench areas where the sno...

Don't be fooled by the relatively modest water equivalent rates in the upper elevations of the Cottonwoods today. The mountains are having a dramatic influence on this storm, but more in the lower elevations. The word orographic means relating to mountains.  When we are talking about orographic precipitation or orographic effects, we mean precipitation or effects related to the mountains. The orographic effects today are dramatic and pronounced on the radar.  Check out the radar loop below, which covers the period from 1938–2144 UTC (1238–1444 MST).  In the northwesterly flow, there is clear enhancement of precipitation on the windward side of the Cedar, Stansbury, Oquirrh, and Wasatch Ranges as one moves from west to east across roughly the center of the image. Note also that there's shadowing on the east (downstream) side of those ranges too. If one looks carefully over the Stansbury, Oquirrh, and Wasatch ranges, however, the highest returns are not found ov...

There are a couple of good opportunities to learn about Wasatch weather and climate this week.  Surely you are interested after todays storm? At 7:30 PM on Wednesday evening, UAC Forecaster Drew Hardesty and University of Utah Professor and fellow Wasatch Weather Weenie Larry Dunn will be giving a fireside chat entitled "Predict the Pow: Backcountry Meteorology 101" at the Black Diamond Retail Store. Source: Black Diamond and Utah Avalanche Center At 6:00 PM on Thursday evening, I'll be giving a talk on my book Secrets of the Greatest Snow on Earth , with an extended section on the potential impacts of global warming on Wasatch skiing, for the Utah Adventure Journal Speaker Series at the Wildflower Lounge in Snowbird's Iron Blosam Lodge.  Admission is free, but you must be 21 to attend.  Consider making a $5 (or more) donation to the Utah Avalanche Center, which gets you into the drawing for some sponsor schwag.  

A few members of the University of Utah Cross Country Team were out training today.  Love it!

For the overnight and morning stages of this storm, the benches have gotten more snow than the central Wasatch Mountains.  This is true for both total snowfall and water equivalent.  For example, as of 10 am we've had 0.95" of water equivalent at our observing site here at the University of Utah campus, whereas only 0.47" has fallen at Alta-Collins. We don't completely understand why we get these upside down storm periods, but there are some common threads.  First, they nearly always feature light, shallow, northwesterly flow.  Below is a radar image from earlier this morning showing surface observations with predominantly W or NW flow.  I've highlighted three boxes.  The westernmost box is on the west side of the Oquirrhs.  Note the precipitation enhancement there.  The central box is over the east bench of the Salt Lake Valley.  Note the precipitation enhancement there as well (plus further north along the northern Wasatch Front.  F...

As expected, a winter storm moved into northern Utah overnight and is giving us the best storm of the season so far.  Based on reports to the National Weather Service, there are some impressive snow totals on the benches including 13 inches on the Bountiful Bench (as of 6 am), 12 inches in Cottonwood Heights (as of 6 am), 7 inches in the upper Avenues (as of 6 am).  In the mountains, Snowbasin Middle Bowl was at 10 inches as of 5 am and Alta-Collins sits at 7 inches as of 7 am. I suspect the snow at Snowbasin was heaviest during the southwesterly crest-level flow overnight. The heavy bench snow, however, is very consistent with what we've seen on radar since the low-level flow shifted to northwesterly.  Note how the highest returns are on the benches west of the Stansbury, Oquirrh, and Wasatch Mountains, especially in the terrain concavities near Bountiful/North Salt Lake and the mouths of the Cottonwoods. Mountain precipitation rates haven't been as great in the c...

I've been out skiing and lack the time to put together a proper forecast for tomorrow.   Below is the winter storm watch issued early this morning by the National Weather Service.  This is going to be a statewide storm with significant travel impacts.  Plan on a rough commute in the morning, and hope for the best. The NWS forecast for the mountains looks pretty good as well.  This will probably be the biggest storm of the season so far (although that's a fairly low bar, with water totals somewhere in the 1-2 inch range by 5 PM Tuesday. Enjoy the storm and be careful out there.

" New agreement is just words.  We're still on a business-as-usual course. " - Jim Hansen Today representatives of 195 nations approved an agreement that commits every country to reduce greenhouse gas emissions.  The full document, available here , recognizes that climate change "represents and urgent and potentially irreversible threat to human societies" and that "deep reductions in global [greenhouse gas] emissions will be required."  The agreement seeks to hold the global average temperature "to well below 2ºC above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5ºC above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change."   In case you are wondering we are currently about 0.8ºC above pre-industrial levels [2015 is a full 1ºC above pre-industrial levels, although that's partly due to the intense El Nino], with additional wa...