Wasatch Weather Weenies

Source: whimquarterly.com Every year in the spring, there is a vocal minority that complains about daylight savings time.  Some don't like the "hangover" from the time change.  Others think it is some government conspiracy. I think these people are all nuts . The problem with daylight savings time isn't that it starts, but that it ends . If I were King, I would make daylight savings time permanent for the entire calendar year . Why do we even bother with standard time?  Who cares if the sun is at its highest point around noon? What I care about is recreation, and I like it when the light lingers after I get home from work.  I can do that this time of year when we are on daylight savings time, but not standard time. Yesterday I was out for a walk in the foothills until almost 6:30 PM and it was light out.  How enjoyable.  Next week, it will be a walk in the dark.  Why must we suffer in this fashion? What are the arguments for going on da...

The last gasp of this week's storm is motoring through the Salt Lake Valley this morning in the form of lake-effect rain and snow showers. The early season snow is partly a blessing for upper-elevation north-facing terrain where it is likely to linger and serve as base for our next storm.  It could, however, be a curse as well. The Utah Avalanche Center reported the first avalanches of the year yesterday, all triggering on weak, faceted snow left over from the storm earlier in October.  That weak snow probably won't strengthen much the next few days and we now have a thin snowpack on other aspects.   The ideal situation for a strong snowpack at the beginning of the season is to have it start snowing and not stop until the snowpack is deep enough to prevent the formation of weak, faceted crystals near the ground.  The worst case scenario is to have a thin snowpack linger and weaken, which often happens after storms in October.  This creates plenty of b...

This time of year when ski area and snow safety operations are still a few weeks away, we rely on a very small number of automated stations to provide us with information on snowfall in the mountains.  In addition, automated snow-depth gauges tend to be a bit sketchier when the snow depth is low.  Therefore, there's more uncertainty than usual in determining how much snow fell last night. The Snowbird SNOTEL came in with about 1.3" of snow-water equivalent after temperatures dropped to near 32ºF.  The automated snow depth sensor was fluctuating around an inch prior to the storm, and currently measures 13 inches after a peak at 14 inches.   Alta–Collins recorded a bit less.  The total snow depth increased from 12–15 inches prior to the storm (pick your favorite, note that this depth sensor read 6 inches when the ground was bare a couple of weeks ago, so deduct 6 for a snow depth estimate) to 24 inches at last observation.  The interval stake reco...

Salt Lakers enjoyed a spectacular sunrise this morning, but as the old saying goes, red sky in morning, sailors take warning.  The winds of change are upon us and our long run of sunny fall weather is coming to an end. Sowing the seeds for this change is a trough that dug rapidly and deepened over the Great Basin overnight last night.  This is a classic case of what meteorologists call  downstream development  in which the ridge over the Gulf of Alaska amplifies followed by trough amplification over the western U.S., as shown in the 500-mb geopotential height loop below which covers the 48-hour period ending at 1200 UTC (0600 MDT) this morning. The trough amplification has led to gusty winds over much of Utah.  Over the past 6 hours, peak gusts reported to MesoWest include 61 miles per hour at Cedar City, 54 miles per hour at Stockton Bar (Tooele Valley), and 52 miles per hour at Dugway Proving Grounds.  The deepening low has also generated a mod...

Downtown Salt Lake City from the Avenues Foothills, 5:24 PM October 24, 2013 Over the past few days, PM2.5 levels in Salt Lake City have been gradually climbing.  They reached a maximum hourly value of 27.3 ug/m3 yesterday afternoon and the 24-h average reached at 16.2 ug/m3 this morning.  That's below the National Ambient Air Quality Standard, but still high enough to put us into the "Moderate" air quality category. Source: Utah Division of Air Quality Such elevated values are unusual but not unheard of.  The plot below shows the percent of days that PM2.5 exceeded 17.5 ug/m3 and 35 ug/m3 versus the week of the year from 1999–2011.  We currently sit in week -10 (negative implies weeks prior to the first week of January).  From 1999–2011, days with PM2.5 (presumably 24-h average) exceeding 17.5 ug/m3 represent about 2% of the days (probably 2 of the 84 days that make up all the week -10s during the 12 year period).  Note that as I write this we ...

Given that the weather in Salt Lake continues to be dominated by the passage of just some occasional "cirrus monotonous", I'm looking elsewhere for some interesting weather and the winner is Alaska.  Things are setting up for a major surge of moisture into south central Alaska.  The 0600 UTC GFS shows the setup with a pronounced upper-level short-wave trough approaching the state from the southwest at 1200 UTC 28 October (4 AM Alaska time Monday morning) and low-level fetch extending from the tropics over the Gulf of Alaska and into the state's interior. What is most impressive about forecasts of this event is the penetration of moisture into the high latitudes.  Over interior Alaska and the Yukon, for example, the forecast precipitable water (a measure of the total water vapor in the atmosphere) reaches 0.5 to 0.75 inches at 4 AM Monday morning (solid contours below).  Such values aren't all that unusual over the Gulf of Alaska, but are unusual for this ...

Pollution over the Salt Lake Valley as viewed from above Big Cottonwood Canyon, October 23, 2013 Paraphrasing Hunter S. Thompson seems appropriate today as my fear and loathing of the wintertime inversion are on the rise.  It's October and we are already seeing pollution in the valley, as one can plainly see looking out the window or in the photo above.  October!  PM2.5 concentrations in the Salt Lake Valley are not as high as they reach during winter inversions, but they are elevated, reaching about 18 ug/m3 yesterday. Source: DAQ Perhaps it's just me, but it seems like we are more susceptible to events like this than we were 10–15 years ago.  We do have a big ridge in place, but perhaps emissions have reached a point where we're seeing a creep of the pollution season into earlier in the fall and later in the winter.  Events are infrequent enough to make trend detection difficult, but perhaps an adventurous reader out there can dig into the numbers a...

Utah has not has a year with a statewide average temperature below that of the 20th century mean since 1993. Source: NCDC That is quite a run and it reflects a warming climate. However, so far this year is very close to that 20th century mean, so the next several weeks will determine if the streak will continue.  In northern Utah, we had a remarkably cold January followed by a remarkably hot summer.  The extremes in southern Utah haven't been quite so pronounced.  When you put all of this together, the statewide average temperature for January–September is just a shade (< 1ºF) above the mean for the same period during the 20th century. Source: NCDC If we can eke it out, that would give us 20 consecutive years with statewide average temperatures above the 20th century mean.  If Utah's climate wasn't changing and remained equivalent to that of the 20th century, the odds of that occurring are about 1 in a million (basically, the same as flipping a coin ...

Source: American Meteorological Society Congratulations to University of Utah Atmospheric Sciences Professor Dave Whiteman and Alpinist Rolando Garibotti who have the cover article of the latest Bulletin of the American Meteorological Society, which explores the characteristics and formation mechanisms of rime mushrooms.  Rime mushrooms are mushroom-shaped formations of hard ice that form on mountain summits and ridges.  They are especially prevalent in Patagonia and other maritime alpine regions, where they frequently pose a challenge for mountaineers.  Click here to access the article, which should be publicly accessible.  Although in a technical journal, the article is quite readable and contains some great photos.

Meteorologists in Utah can take some time off as a ginormous ridge will dominate our weather through the week.  Below is the 12-hour forecast from last night's North American Ensemble Prediction System (NAEFS) showing the situation this morning, followed by the 120 hour forecast valid at 6 PM Friday.  There's very little change in the overall pattern with a high amplitude, long wave ridge firmly ensconced over the western U.S. Source: NWS Source: NWS Looks like a good week to be in southern Utah if you are so fortunate.

Looking south from the Avenues Foothills, 1250 MDT October 19, 2013 Although we are not yet in the inversion season, we are now nearly a full month past the fall equinox, days are shorter than nights, and the sun is getting low on the horizon.  As a result, we're simply not able to mix out the air over the Salt Lake Valley very vigorously, and the net result is a touch of smog.  The sounding taken from the Salt Lake City airport yesterday afternoon shows that the surface-based mixed layer extended to about 750 mb (~8500 ft), where a stable layer basically put a "cap" on the valley atmosphere.  The base of that cap was very near the visual top of the densest smog in the photo above. Source: SPC The difference between yesterday and a full blown wintertime smog event is the height and strength of the inversion or stable layer.  Yesterday's stable layer was fairly high, so pollutants were dispersed through a fairly deep layer and there was some transport o...

High country snow on north facing aspects above Mill Creek Canyon, October 18, 2013 As so often happens in Utah during October, and early season snowstorm is followed by an extended period of splendid fall weather.  The long-range forecast models suggest that the dry weather we've experienced the past couple of days will persist for at least several days more as both the GFS ensemble (upper left panel) and the ECMWF ensemble (lower left) keep us under the influence of a high amplitude ridge through the middle of next week. Source: NWS Even longer range forecasts suggest that this dry weather may continue even longer, although we'll have to see if that comes to fruition.  One thing is certain, the snow that currently exists on south, west, or east facing aspects is toast.  The $64,000 question is what will happen to the snow on upper-elevation slopes facing the northern half of the compass.  It's tough to melt snow this time of year on those aspects.  ...

Editor's Note : Special thanks to Jeff Massey for contributions to this post.   Today marks the 29th anniversary of one of the largest snowstorms to hit the Wasatch Front.  It desperately needs a name, but to my knowledge one hasn't been coined, so we'll just call it that Great Storm of October 1984 . A brief analysis of the Great Storm was produced by David Carpenter and published in the journal Weather and Forecasting in 1993 ( Carpenter 1993 ).  David is now the meteorologist-in-charge at the Rapid City National Weather Service Forecast Office and recently made headlines for h is office's dedication to public service when a huge blizzard hit western South Dakota during the federal government shutdown . In the Salt Lake Valley, the Great Storm was a beast, producing 18 inches at the Salt Lake City airport, 27 inches inOlympus Cove, and 25 inches in Cottonwood Heights.  The heaviest accumulation was along the east bench, whereas there were locations in the we...

Today marks the first day of our field activities for the Ontario Winter Lake-effect Systems (OWLeS) field program.  Two of my graduate students, Leah Campbell and Peter Veals, arrived in Syracuse, NY last night and will be installing equipment over the next several days. OWLeS (yes, lower case e) is a National Science Foundation sponsored field program examining the formation mechanisms, cloud microphysics, precipitation dynamics, and terrain enhancement of lake-effect systems ( http://www.owles.org ).  We are specifically examining "short-axis" lake-effect systems that form when the wind flows across the long axis of Lake Ontario, "long-axis" lake-effect systems that form when the wind flows along the long axis of Lake Ontario, and the enhancement of long-axis lake-effect systems over the Tug Hill Plateau. Participants include the University of Utah, University of Wyoming, University of Illinois, SUNY Oswego, Hobart and William Smith Colleges, Millersville...

A phenomenon that I frequently see from the Avenues on cool mornings is a pronounced pool of haze when I look southward over the Holladay and Cottonwood Heights area. Here's a closeup showing a fairly distinct northern edge. For such a haze pool to form, one typically needs high relative humidities, so a cool morning after a storm is best.  I've always assumed that the northern edge of the haze pool lies at the southern edge of the outflow from Parley's canyon.  There is some evidence supporting this view in this morning's MesoWest observations.  Note in particular the 15 knot exit jet near Parley's Canyon, whereas the flow is weaker to the south in Holladay and southern Olympus Cove.  In addition, the outflow from Parley's canyon is warmer (39ºF) and drier (RH=64%, not shown) compared to the airmass over Holladay and southern Olympus Cove where it is cooler 30–36ºF (RH=87–100%). Source: Mesowest Haze typically needs a relative humidity of at lea...

One of my pet peeves it the use of the word "normal" to describe climate averages.  Even The Weather Channel has raised concerns about this , yet it is commonly done by the National Weather Service and television broadcasters to describe the weather statistics on any given day. It is perfectly "normal" in the midlatitudes for the weather to fluctuate.  The average weather for any given day does not equal normal. Over the past 31 days, we have had a very good example of this.  In fact, during the past 31 days we have had about as close to "normal" weather as we can have in late sumer and early fall.  The temperatures at the Salt Lake City International Airport have fluctuated up and down with a gradual cooling trend as we moved through September and early October.  There have been days with above average temperatures, and days with below average temperatures, but the fluctuations have not been extreme (only one record was tied during this period). ...

Early last week, the Climate Prediction Center issued its monthly El Niño/Southern Oscillation (ENSO) diagnostic discussion, confirming earlier forecasts for "ENSO-neutral" conditions to continue through spring 2014.  ENSO-neutral means that neither El Niño nor La Niña conditions will predominate. For the Wasatch Range, this means little.  We discussed last month how little correlation there is between snowfall at Alta and ENSO (see Outlook for the 2013–2014 Ski Season ), as illustrated by the reproduced figure below. Three month (NDJ, DJF, JFM, FMA) accumulated snowfall at Alta–Guard vs. the corresponding ENSO index.  Courtesy Jeff Massey. So, regardless of what you see in the news, or crazy ideas about caterpillar fur or groundhogs, nobody can say with any reliability what this year will be like in the Cottonwoods  We have roughly equal chances of a below average, average, or above average snow year.

Fall Break for the University of Utah students is almost here.  The annual pilgrimage to southern Utah and the Colorado Plateau begins for some today and continues the next few days.  There is an embarrassment of riches to choose from.  Perhaps you have a permit visit the wave or are just planning a trip to one of the National Parks.  Ah, what a great trip it could be, if our inept Congress could just get their act together and pass a budget or continuing resolution.   Should that happen, or you are targeting other great destinations that remain open for "business" (e.g., the San Rafeal Swell), here's a quick-and-dirty outlook.  The main fly in the ointment is a trough that pushes into southern and central Utah late Sunday and affects the weather through Monday.  Right now, precipitation extends down to about Cedar City and Moab, but keep an eye on the forecast in case this changes.  Be prepared for changeable conditions for Sunday to Monday. ...

The loop below shows the IR satellite imagery and 500-mb height analysis for the 2-day period ending this morning.  It shows an outstanding example of what meteorologists refer to as a digging trough .   A 500-mb height analysis is essentially a topographic map, except instead of showing the elevation of the terrain, it shows you the elevation of the 500-mb pressure level.  Troughs are areas where the 500-mb level is locally low, and ridges are areas where the 500-mb level is locally high.  The flow roughly parallels the height contours with lower heights on the left and is stronger in areas where the height contours are close together.  Thus, a meteorologist can look at a map like the one above and quickly ascertain the large-scale flow and how it has been evolving (or, see how it will evolve in the future using a model 500-mb height forecast). A digging trough moves very strongly southward and often amplifies, forming a closed low center.  One can ...

Yours truly blows off a day of graduate school for turns at Crystal Mountain, Washington. Skis: K2 KVCs.  Boots: Salomon SX-91 (yeah, rear entry).  Poles: Kerma "corrective angle." Yes, that is a flourescent pink turtleneck.  Jealous?  April 1991. As I was going through some old photos the other day I thought of two things.  First, I'm really glad I didn't grow up in the digital photography era.  Some things are best left to hazy memories or personal photo albums.  Pity you youngsters out there.  Second, I can remember every pair of skis that I've owned, although a couple of the model names remain a bit unclear.  Below is my lifetime in skis.  Feel free to comment and share some of your most memorable boards. Trek XC skis (circa 1979): My first "boards" were skinny skis as my parents took up cross-country skiing when I was in my early teens.  I can't remember the model, but they were grey, nowax, and very slow. ...