Wasatch Weather Weenies

One of the more exciting developments over the past few years in my field has been the development of applications that can integrate data from ground-based radars, space-borne radars, precipitation gauges, and other platforms to produce very detailed analyses of the three-dimensional structure of precipitation systems and the accumulation of precipitation on the ground. One such system, which radar and precipitation junkies can access and play with at nmq.ou.edu , is the Multi-Radar Multi-Sensor System (MRMS) developed as a joint initiative between the National Severe Storms Lab, FAA, National Weather Service, and the University of Oklahoma Cooperative Institute in Mesoscale Meteorological Studies.  The MRMS allows one to examine historical (beginning July 2013) or real-time storms, which is great for both researchers and weather junkies. Here are a few snippets from the system.  I'll concentrate on a particularly intense lake-effect storm that we examined during the Nati...

Wednesday night was remarkably warm, with an overnight low at the Salt Lake City Airport of 74ºF, good enough for a record high minimum temperature for both the day and the month, or was it? Source: NWS. As noted in the NWS statement above (see the * and +) records at the Salt Lake City airport are based on the calendar day (i.e., midnight to midnight).  As such, the low temperature for the day can occur at any time during that period.  So what happened before midnight last night?  There was a cold-frontal passage just before midnight, but temperatures remained quite high, dropping to only 73ºF by midnight.  Still good for a record right?   Nope.  The calendar day is defined using standard time and we are currently on daylight time.  Midnight standard time is actually 1 AM daylight time.  By 1 AM, the temperature fell to 67ºF and that stands as our official non-record minimum for the day.     Easy come, easy go. ...

Source: sltrib.com As discussed in over the weekend in the Salt Lake Tribune , Salt Lake City Mayor Ralph Becker is proposing to eliminate city support for July 4 and July 24 (Pioneer Day) fireworks at Liberty and Jordan Parks, suggesting it would be a symbolic measure for combatting poor air quality.  Not surprisingly, this has proven to be a controversial proposal, setting off fireworks with the city council. We have discussed this issue previously, especially after this past New Years Eve when numerous fireworks displays went off despite wide-spread poor air quality.  This led to a measurable increase in PM2.5, making a bad air quality episode even worse.  Although I am less concerned with summertime fireworks when mixing is typically more vigorous, their impact on air quality has been documented and it would make sense to curtail them in situations where the air quality is degraded and we don't want to add insult to injury. Below is a repost of the  ...

With a likely high at or perhaps just above 90ºF at the Salt Lake City airport this afternoon, I guess we can say that summer starts today.  Tomorrow looks to be a hot one as well, with stronger southerly flow and the possibility that we may see some dust blowing in from the Sevier desert and lake bed. The pattern through Saturday is characterized by troughing over the west coast with Utah in warm, dry southwesterly flow, as illustrated by the ECMWF forecasts for Thursday afternoon (00UTC Friday), and Saturday afternoon (00UTC Sunday) below. Thus, even though tomorrow (Wednesday) looks to be the warmest day of the week, above average temperatures and dry conditions are likely to persist through Saturday.  If you've been putting off sprinkler maintenance, this will be the week to get caught up.  

A feature sometimes referred to as a deformation band has been sitting over the Salt Lake Valley all morning, spoiling the start of the Memorial Day Weekend. Such features sometimes develop to the northeast of closed upper-level lows, as is the case today, where there is a subtle shift in the wind.  Note in the image below the slight shift in the wind from northerly or northeasterly to the northwest of the band and more easterly to the east of the band. These bands tend to be slow moving, and that's why we've been stuck in the rain all morning.  In winter, a band like this can create all sorts of problems as the snow piles up in a narrow corridor.  Today, it's just ruining everyone's golf and picnic plans.

My son was off school today so we decided to beat the weekend rush for first turns in the Wasatch (ha ha) and go for an early morning tour.  Thanks to this winter's dust storms and Alta preparing to improve the trails in the Corkscrew/Nina's Curve area, the base was rather unappetizing.   Things looked only marginally better a bit further up the mountain as the impacts from this spring's dust storms are readily apparent and the snowcover is quite dirty.  What a shame.   The view of a a few lingering patches of "white corn" mixed in with snirt. Despite the unappealing color, the snow is well consolidated and skied reasonably well. The forecast hasn't changed much from my Wednesday update, except that the "pesky trough" is perhaps lingering over the state a bit longer.  Looks like some showers and thunderstorms statewide tomorrow, southern and eastern Utah on Sunday, and perhaps some lingering stuff on Monday.  Afternoon will ...

It was just 10 days ago that we were talking about snow across much of the central Rocky Mountain region, including several inches in the Denver Metropolitan area (see It's Not Over Until We Say It's Over ).  My how things have changed as yesterday a remarkable supercell thunderstorm moved through the Denver Metropolitan area, resulting in a tornado warning for an area that included the Denver International Airport. Some great photos of the storm are available from thedenverchannel.com .  As of this morning, the Storm Prediction lists 9 tornado reports from the area. The Doppler velocity image below shows the remarkable mesocyclone that accompanied the storm with green indicating flow towards the radar (lighter green indicates stronger flow towards the radar) and red indicating flow away from the radar.  A mesocyclone is a storm-scale area of strong rotation.  At this time, the counterclockwise circulation associated with the mesocyclone is centered to the im...

A pesky upper-level trough is presently sitting over and bringing showers to Nevada.  This trough is the main fly in the ointment for the Memorial Day weekend forecast as it is expected to slowly move across the southwest United States bringing with it a chance of showers and thunderstorms. The track, intensity, and speed of the upper-level trough has been subject to uncertainty the past few days.  Overnight runs from the North American Ensemble Forecast System (NAEFS) and ECMWF ensemble system center the trough just south of the four corners by 0000 UTC Sunday (6 PM MDT Saturday). Source: Environment Canada Source: ECMWF The system is not particularly strong, but contains sufficient moisture, instability, and dynamics to bring a threat of showers and thunderstorms to the southern and eastern portions of Utah on Friday and Saturday, with a lingering threat in the far southeastern part of the state on Sunday.  Keep an eye on the forecasts and an eye to the sky....

A pretty good guess for the rate of snowmelt in a mature snowpack on north facing aspects in the Wasatch Mountains in late spring and early summer is 2–2.5 inches a day.  Obviously this changes depending on the weather and snow conditions (for instance, how dusty and dirty it is) but it works pretty well in patterns like these and is a pretty good guess for the rate of snow loss this time of year.   The gradual demise of the snowpack at Alta-Collins can be seen in the 7-day trace of hourly snow depth measurements below. Source: Alta–Collins The drop over this 7 day period is from 115 to 98 inches, or an average of 2.4 inches per day.  At that rate, we have 41 days until the end of snow at this site, which would be about June 27th.

What a pity. I'm going to guess, and this is purely a guess, that we have enough dust on the snow this year to accelerate the loss of snowcover by about 10 days.  We need to get a snow-energy balance station in the Wasatch so that we can collect the data needed to better quantify the impact of the dust.

The head Wasatch Weather Weenie on a rare ski tour It was a magical day today. First, I got my favorite e-mail from Google.  You know, the one with the header that says: "You have no events scheduled for today."  Oh, how I love it when that happens. Then, my back felt unusually spry once again.  I'm hoping this is a trend, but if not, I decided to go for a short ski tour just in case.  If there was 18" new, the day would have been perfect, but 2 out of 3 ain't bad. As is often the case with spring skiing, timing is everything and we had one great run and one terrible run.  On the ascent, we were quite pleased to find the snirt to be buried and the snow white.  Any hint of yellowing in the photo below is purely an artifact of my poor photography.  The snow had frozen just enough overnight to be supportive. Our timing was perfect for a great run on a south-facing aspect into Snake Creek where we found the turns to be surprisingly good. ...

Over the years, some people have criticized me for emphasizing "bad" aspects of global warming rather than "good" aspects.  Since I am very concerned about global warming, this might partially reflect a personal bias.  However, even though there will be some so-called winners with climate change, negative impacts will exceed positive ones, especially if the climate change is abrupt. Why?  Because our entire society has been built around the climate of the 20th century (and to some degree the climate of the last couple thousand years).  Where we grow crops, how we store and distribute water, where we have built cities, and how we have built infrastructure for resiliency against weather and climate variability are a function of that 20th century climate (and to some degree the climate of the preceding centuries). Here are some examples.  Water is the agent that delivers most climate impacts and even if there are a few winners with climate change, everyone lose...

I suspect there won't be many people out and about in the Wasatch Backcountry the next few days, but if you are heading out, let's be careful out there.  Conditions are ripe for wet spring slides.  Over the past week, the snowfall at upper-elevations contained about 3 inches of water, quite a dumpage for May when you consider that the monthly average precipitation for May at Alta is 3.86 inches.   Source: Alta-Collins Now we are going to warm it up.  Temperatures in the upper elevations will be climbing each day for the rest of the week and the nightly freeze will become weaker and weaker.  Temperatures at 11,000 feet will be solidly in the 40s by late Thursday through Saturday, and it will be much warmer than that at lower elevations. Source: weather.utah.edu The gradual rise is perhaps better than an abrupt shift, but still, one needs to be cautious when going from big spring dumpage to a big spring warmup.

The ski season this spring has been quite a roller coaster. Source: http://www.telegraph.co.uk/news/newstopics/howaboutthat/5881002/Man-skates-down-roller-coaster.html Spring is known for ups and downs, but this spring has been especially interesting as we've had fluctuations from high amplitude ridges, accompanied by several days of warm sunny weather, to cold troughs that produce significant mountain snows.   As a result, the evolution of the snowpack in the central Wasatch this winter looks like one of those old wooden roller coasters with a long climb to great heights, followed by a series of drops and climbs.  This is especially apparent at the Brighton and Thaynes Canyon (mid-mountain Park City) SNOTEL stations where peak snowpack snow-water equivalent (SWE) occurred in early April, but you can see two sharp recoveries following storms in late April and mid May (green line is this winter, red last winter, blue average, and purple median).     ...

For Colorado, Utah, and Wyoming, Mother Nature is pulling a Bluto Blutarski and declaring that winter is "nothing is over until we decide it is!"  Warning, the clip above includes strong language, but also a good history lesson. The calendar may say May 12th, but a major winter storm has just rumbled through the central Rockies. Below are some daily snowfall observations provided to the Community Collaborative Rain, Hail, & Snow Network (a.k.a., CoCoRaHS ) this morning in Colorado.  Accumulations in Denver area of up 9 inches, in the front range of up to 20 inches, and near Kremmling in Grand County of up to 22 inches. Source: CoCoRaHS Ah, spring in the Rockies.  As Al Pacino said in the Godfather, "just when I think I'm out, they pull me back in!."  It will be interesting to see the storm totals as snow is still falling in places. The average monthly snowfall in Denver features a peak of 11.5 inches in March, with April being the 2nd snowiest...

Snow is falling in the mid and upper elevations across most of the state today.  Here's some web cam eye candy. Alta. 5 inches new overnight.  This could be the last powder day of the season, although perhaps the snow will hang on through tomorrow. Get on it. Soldier Summit. Rattlesnake Bench, I-70, San Rafael Swell. Boulder Summit south of Torrey. SR-14 east of Cedar City.

Some good turns were had at upper elevations today My balky back has kept me from ski touring for most of the year, but I felt unusually spry this morning so I got out to sample some of Mother Nature's late-season offerings.  I was glad I did.  For May 10th, the skiing was just fine with some heavy powder above 9500 feet and some surprisingly smooth Cascade concrete at lower elevations.  The tracks in the Baldy Main Chute above aren't mine, but show why it pays to never give up on the ski season.  Further, we've now buried the dust layer under a couple inches of water equivalent, so maybe we'll have a few days of decent "white" corn once things start to warm up. There's a decent chance that this weekend will provide our last flirtation with freshies for the season.  A monster ridge builds in over the west next week. Although there's always the possibility of a cold storm in late May or June, perhaps that's all she wrote for the 2013–14...

A nice thunderstorm is rolling onto campus as I write this (12:15 MDT).  Here's a view as it approached from the northwest Source: www.timecam.tv and a recent radar image. Source: NCAR/RAL Thunder and lightning abound, as well as some really cool cloud interactions with the terrain (sorry, no photos).  Enjoy from indoors!