Wasatch Weather Weenies

Surely you remember it.  That unbelievable low altitude snowpack we had this winter.  I do.  This is what the Avenues foothills looked like on January 11. Here's the view up City Creek Canyon from the Avenues foothills today. City Creek Canyon is one of several that provides water for the Salt Lake Valley.  Things are looking grim for runoff this year.  There is a SNOTEL station at 8200 feet in City Creek on the slopes of Lookout Peak, the snowy mountain on the horizon in the photo above.  With a snowpack SWE of 18.8 inches, it presently sits at only 73% of average for today. Source: NWS/CBRFC

Next to powder, I don't think there's much better about living in Utah than spring.  My guess is that pretty much everyone felt good to be alive as they soaked up the rays today. For those of you who have given up on the ski season, you're missing out on a decent corn harvest.   The conditions at Alta were pretty good this afternoon, especially on the steeps.  And, without much of a crowd, there's quite a bit of elbow room on the groomers.  If you can't ski good, ski fast, and that's what we did for much of the day. On the way home we ran across this snowboarder.  Perhaps he is auditioning for Easy Rider II.

The 2014 Olympic Winter Games will be held in Sochi, Russia next February.  Sochi lies on the northeast shore of the Black Sea, near the Russian border with Georgia. Nordic, Alpine, and Freestyle ski events, along with snowboarding, bobsledding, and ski jumping events will be held within the so called "Mountain Cluster" in the Caucasus Mountains east of Sochi.  I suspect that the organizers will rue the day that they named their venue areas clusters.  Jon Stewart should have a field day next winter. Source: http://www.sochi2014.com The weather and climate of Sochi is already getting attention, including an article earlier this week in the New York Times discussing how organizers are already making and stockpiling snow for next year ! Source: New York Times Much has been made of the fact that one can find palm trees in Sochi.   How can you have a Winter Olympics in a place where there are palm trees?  However, palm trees are not exclusively...

Our brief flirtation with winter is over and while the snow was greatly appreciated by skiers, it put only a small dent (if that) in the snowpack deficit that presently exists in the central Wasatch and elsewhere in the western U.S. The latest snowpack snow-water equivalent analysis shows only a handful of basins presently sit above average.  These basins are located in the Olympic and Cascade Mountains, as well as interior ranges near the Canadian border.  All basins in the upper Colorado and Great Basin are below average. In the central Wasatch, Snowbird, Mill D North, and Thaynes Canyon are at 77–84% of average.  Although Mill D and Thaynes Canyon are thankfully above last year, Snowbird is pretty much neck-and-neck with it. Source: NWS/CBRFC April 1st is not only April fools day, but typically an important date for anticipating the spring runoff.  It is close to the average time of peak snowpack at many locations in the west, although that peak i...

Here are four great reasons to study at the University of Utah, courtesy of Wasatch Magazine.  Photo at upper right should be credited to U alum Trevor Alcott.  I could never take such an iconic photo.   Source: Wasatch Magazine

Over the past few days, we have experienced a potpourri of convection , updrafts that transfer heat and moisture vertically in the atmosphere and lead to the generation of cumulus clouds and snow showers.  Depending on the place and time, this convection was produced by the Great Salt Lake, daytime surface heating, and/or flow over the mountains. After a day of skiing yesterday, I visited Antelope Island State Park today.  Antelope Island is a spectacular place, especially in the spring.  The grass is just starting to green up, so the next few weeks are prime time for a visit. Here are some perspectives on todays convection.  Orographic convection bubbled over the Wasatch Mountains at about 11 am MDT due to flow over the mountains and/or weak thermal forcing.  The accompanying radar shows the weak echoes over the mountains. Radar Source: NCAR/RAL At 11:35 AM MDT, some beautiful cumulus clouds developed over Frary Peak.  They are carried southea...

The lake effect and orographic snowshowers got Alta-Collins to a 103 inch settled snow depth.  Whoot whoot!

Some musings about lake effect, beginning with observations of yesterday's lake band.  First, here's a video of the snow squall that came through late yesterday morning, courtesy of George Wilkerson and Steve Krueger. Here are a few photos from Peter Veals of the event as well.   Source: Peter Veals   Today we have snow showers in the area, but the role of the lake is debatable.  There is some evidence of more frequent and persistent returns downstream of the lake, but it is relatively unorganized and there is scattered precipitation in areas not downstream of the lake as well (this precipitation extends northward into southeast Idaho).  I'll call today weakly lake enhanced.   The models suggest a pattern favorable for lake-effect tonight, with cold, moist, northwesterly flow moving over the Great Salt Lake as shown, for example, in the NAM forecast for 1200 UTC (0600 MDT) tomorrow morning). Historically, such patterns ...

We're seeing some nice lake-effect snow squalls moving off the Great Salt Lake this morning.  Also evident in the radar loop below are persistent orographic snow showers (orographic is just a fancy word for mountain) in the high terrain surrounding the Cottonwoods. I suspect the lake-effect will weaken and become more scattered this afternoon, as is typically the case during these events, especially in the spring.  The graph below shows how the frequency of lake-effect tends to decline during the day, especially in the spring (purple bars). Number of days with lake-effect at a given time of day. Source: Alcott et al. (2012)

It's good to see a storm finally come through as we've been disappointed one to many times this year and we really needed a refill.  As of 9 am, our Alta-Atwater site near the base of Alta has recorded 0.72 inches of SWE with a settled new-snow depth of about 7 inches.  The Alta-Collins snowstake about 1000 feet higher recorded 0.84" of SWE and about 10 or 11 inches of new snow depending on how you add up the increments.  I've seen higher amounts from a couple of automated high-elevation sensors in upper Big Cottonwood Canyon.  Not a huge dump, but greatly appreciated nonetheless.

Astronomical spring arrives today, but no matter what my daffodils say, meteorological reality will beg to differ in the coming days. This morning we have some snow falling in the mountains and rain in the Salt Lake Valley.  The precipitation began with your classic "cloud storm" scenario.  An incredibly dry airmass was in place over the Salt Lake Valley this morning, so much of the early precipitation evaporated before reaching the ground.  In this morning's sounding, taken about 5 am MDT, there was a 34ºF dewpoint depression at the surface (which equates to a relative humidity of 25%) and even drier air just above the surface layer. Source: NOAA/NWS/SPC A cold front moves in tonight, followed by a prolonged period of northwesterly flow that will gradually bring in even colder air on Thursday and Friday.  By Saturday morning, our 700-mb temperatures are forecast to be about -16ºC, which is below average even for January. The overall change in ...

Public forecasts issued by the National Weather Service and most news broadcasts are usually fairly vague with regards to snow accumulations.  They usually provide a range (e.g., 4-8 inches) for a broad period of time (e.g., tomorrow). There are, of course, many users who need far greater precision than that.  Determining how much salt to apply to highway for the morning rush hour, or whether or not to close a canyon to traffic to perform avalanche control work requires knowing very precisely how much snow is going to fall and when.  The temperature and the strength of the wind might also be important for these applications too.   With those examples in mind, let's think about the ramifications of the forecasts being produced for tomorrow (Wednesday) afternoon through Thursday morning by the 12-km NAM and its 4-km high resolution nest, which are remarkably different in terms of the timing and amount of precipitation. For the three-hour period ending at 3 P...

On this day last year, during one of the better storm cycles we had all year, the snow depth at Alta-Collins hit the coveted 100 inch barrier. And the snow depth kept climbing, eventually topping out at 118"on March 20th.  Ah, we'll go dancing in the dark, walking through the park, and reminiscing.  I bet you never thought last year would look so good. Currently we sit at 84 inches at Alta-Collins.  Maybe we can make a run at the coveted 100 inch barrier later this week, when the models advertise a bit more action.  I don't see us catching up to that 118" snow depth, but any refill will be appreciated. And, in case you were wondering, on March 18, 2011 we were sitting on 153 inches, on our way to 200+.

My subjective impression of the 4-km NAM forecast for this morning's 0900–1500 UTC (0300–0900 MDT) period discussed in the previous post is that it was far too wet in both the mountains and the lowlands.  Here are a few precipitation observations for the period, which are all less than what was produced by the 4-km NAM. Ogden: T Salt Lake City: T Alta-Collins: .09" Alta-Atwater: .12" Alta-Guard: .16" Lookout Peak: ~.20" Ben Lomond Peak: ~.10" Powder Mountain: ~.11" Call this false alarm (i.e., overforecast) #1.  We'll see how it does in future events, but I'm going to guess we are going to see more of this, especially in the mountains, although there will eventually be a moment of glory when it nails a big one.

Earlier this week, we started downloading and processing forecasts from the NAM high-resolution nest, which covers the continental US at 4-km grid spacing, which is three times the resolution of the regular NAM. We will start to see if the greater resolution proves useful for Wasatch forecasting over the next few weeks.  During the 2002 Winter Olympics, we found that a 4-km model did produce more accurate precipitation forecasts over northern Utah than a 12-km model, but also with more false alarms.   The 4-km model got more forecasts right, but when it was wrong, it was a disaster.  Thus, like a well-designed golf hole, resolution offers up risks and rewards. We have a dust-on-crust storm in the offing for tomorrow, so I thought we would do a quick comparison.  First the 12-km, which lumps all the major mountains of northern Utah, including the Stansburys, Oquirrhs, Wasatch, and Uintas, into a single broad mountain that is highest where the western Uintas sit. ...

DModel/DT is calculus-based slang that meteorologists use to describe a trend in model forecasts.  For example, the GFS forecast from 0600 UTC 12 March showed a less than favorable forecast for snow in the Wasatch late Saturday night and Sunday morning, with a short-weve trough over the Pacific Northwest and Utah under the influence of a short-wave ridge.  Subsequent forecasts, however, have pushed the short-wave trough further east and sagged the storm-track southward, resulting in snow over the Wasatch late Saturday night and Sunday morning.  This model trend is illustrated in the DModel/DT loop below, which is based on 0600 UTC initialized GFS forecasts from the past four days all verifying at 1200 UTC 17 March (Sunday).   Note how each successive forecast produces more precipitation over northern Utah. You have to be careful when using DModel/DT because the existence of a trend doesn't necessarily mean that the trend will continue in future forecasts. ...

Following up on the previous post, the National Weather Service reports that we've hit 71ºF at the Salt Lake City airport, breaking the previous record that was set in 1935.  If you are wondering, I think the all-time record for March is 80ºF, which we set March 31, 2012.  That record is safe.

That 70's Show airs today, but it might not be available from your cable provider. For example, you might want to avoid going near the Great Salt Lake.  The lake is quite cold right now as illustrated by temperatures from 4 PM yesterday afternoon.  While it was 67ºF at the Salt Lake City airport, it was only 54ºF at the Saltair marina, 53ºF at Hat Island, and 51ºF at Gunnison Island. Source: MesoWest That's an impressively cold airmass sitting over the lake and it will be there today too. Another cool spot was the Cache Valley where the high at the Logan Airport only reached 50ºF.  The issue there is snow cover, as can be seen in yesterday afternoon's MODIS image. Source: NASA They even had some fog yesterday morning and this morning, which can just be made out along the valley floor in this Utah State webcam image. Source: Utah State University All of this provides a good example of how the state of the land and lake surfaces can affect the local...

Asheville, NC, March 14, 1993.  Source: NOAA This week marks the 20th anniversary of the 1993 Superstorm, one of the biggest snowstorms ever in the eastern United States and a seminal moment in modern weather forecasting. As summarized in the now classic paper by Kocin et al. (1995) , the Superstorm began as disorganized low over the Gulf of Mexico, but deepened 17 mb in 12 hours to reach 984 mb when it was just south of Louisiana.  As it moved up the eastern seaboard, the central pressure dropped to 971 mb over Georgia and 960 mb over Delaware.  The storm set record low sea level pressures at locations spanning from Georgia to Maine. Source: Kocin et al. (1995) Measurable snow stretched from the Florida Panhandle into southeast Canada, covering an area containing 90 million inhabitants in the eastern U.S.  Accumulations of more than 40 inches were observed at locations in Maryland, New York, North Carolina, Pennsylvania, Tennessee, Vermont, and Wast ...