Wasatch Weather Weenies

Despite my grumblings about frustrating forecasting of hit-and-miss convection, it's been a pretty good May in the Salt Lake Valley.  Any time you can make it until late May with predominantly green foothills you have to be happy. That's about to change. Tomorrow marks the first day of meteorological summer, which covers June, July, and August (sorry astronomers, your seasonal definitions based on solstices and equinoxes are LAME and not used by meteorologists). Not only is tomorrow the first day of summer, but it also will mark a warmup that marks entry into the hottest stretch of weather that we've had all year.  As can be seen in the water vapor image and GFS analysis for 1200 UTC this morning, a high amplitude ridge lurks along the Pacific coast and is moving slowly eastward. Although we've seen some days in the 80s this year, and a max of 88 on May 14, it looks like we will eclipse 90 later in the week and see a sustained stretch of summer-like temperatu...

Frary Peak, high point on Antelope Island I've lived in Utah for more than 20 years and have had Frary Peak on my must hike list for nearly that long.  Perhaps because I've been distracted by spring skiing, I've never gotten around to doing it.  I decided to give it a go this morning, and found it to be one of the most enjoyable hikes that I've done in Utah. I probably missed the green grass and wildflower peak by two weeks, but it was still colorful on north aspects, which the trail frequents as it moves southward along the Frary Peak ridgeline. The summit is hidden for most of the hike, until you are within about a half mile. On the trip I saw bison (on the plains in the distance) and these fellas, which I think are big horn sheep. Summit view of America's great inland sea (i.e., the Great Salt Lake), with the Stansbury Mountains and Deseret Peak in the distance.  For those of you looking for something to do next weekend, the Twin Couloirs ...

I need to pick on myself today for poor lightning safety practices.  Much like avalanche accidents, human factors often come to play in lightning accidents. As I was heading out for a quick mountain bike, a cell was popping over the Oquirrhs.  It wasn't much to be concerned with at the time, but I made a mental note to keep an eye on it.  Plus, I needed to be somewhere later and had to get my ride in. The climb from the valley to the ridge was uneventful, other than running into this not-so-friendly fellow. I know little about snakes, but I come across one about once a month in the warm season.  Usually they are gopher snakes.  I'm not sure what this one was.  It was fairly non-aggressive and wasn't rattling, but a close look at the tail suggested it may have been a rattlesnake that had lost the rattle.  I watched him slither into the grass and kept my distance. Getting back to lightning safety, I didn't hear any thunder on the climb, but on...

Developing thunderstorm over the Oquirrh Mountains yesterday morning It's been a tough go finding something to blog about in the current pattern.  With weak troughing and instability over the region for many many days, we've had nothing but hit-and-miss showers and thunderstorms.  Such patterns are the ultimate in forecasting frustration for me. There's no magic pill you can take to forecast this stuff.  You can go for modest changes in coverage and frequency (e.g., today probably won't be as active as yesterday in the Salt Lake Valley), but even that's fleeting.  A couple of days of this I can live with, but it's been going on for so long I feel like Bill Murray in Groundhog Day! It does look like we'll be getting a drying out and a warming up early next week.  Probably by next Wednesday I'll be wishing for a return of the unsettled weather!

Anyone who follows seasonal predictions, including those critical to Wasatch Weather Weenies like snowfall, is immediately confronted with an acronym stew of climate indices such as ENSO, PNA, AO, NAO, PDO, IPO, QDO, MJO, etc. This post is concerned with the PDO, or Pacific Decadal Oscillation , because I receive many questions and comments regarding its use for seasonal snowfall outlooks over western North America.   What is the PDO? If we skip over the gory statistical details, the PDO is simply the dominant pattern of sea-surface temperature (SST) variability in the North Pacific.  The positive (a.k.a. warm) phase of the PDO features a horseshoe of relatively warm (compared to climatology) SSTs along the west coast of North America and the eastern subtropical North Pacific with relatively cool SSTs over the midlatitude western and central Pacific.   PDO Positive Phase.  Source: Wikipedia . During the "cool" or negative phase, the pattern is rever...

It's a bluebird powder day a few years in the future and you're heading out for a backcountry tour.  You haven't picked a destination yet, so you bring your Mill Creek Pass in case you tour in Mill Creek, your interagency access pass in case you go to Cardiff Fork, your UDOT Snowpark Pass in case you tour Butler Fork, and your Town of Alta Snowpark in case you decide to up-and-over from Alta to Big Cottonwood. You pick up your buddies, decide to tour Wills Hill due to the high avalanche hazard, and decide to park at one of the Park-n-Rides at the bottom of Big Cottonwood.  Unfortunately, you got a late start and the lots are full.  You decide your best bet is to drive. Double unfortunately, it's total gridlock at the bottom of the canyon.  That used to be a thing in Little Cottonwood, but now it's a thing in Big Cottonwood too. So, you inch up Big Cottonwood, but when you get to the Solitude Lot, not only is it $10 to park (that's not covered by your fee p...

Anyone who has read the news won't be surprised to learn that it has been an exceptionally hot northern hemisphere cold season (November to April, hereafter just cold season) globally, especially in the Arctic.  Let's have a quick look at the numbers.  Because I'm being lazy, I'm going to mix two global temperature data sets, one produced by the NASA Goddard Institute for Space Studies (NASA-GISS) and the other produced by the National Centers for Environmental Information (NCEI).  Neither of their web sites produced everything I want, but I can get it if I mix and match. Let's begin with the global temperature anomalies for November to April, which show the past cold season really was quite remarkable, running more than 1ºC (2ºF) above the 20th century average.  The tremendous surge during this period is largely a result of long-term global warming combined with El Nino. Source: NCEI The plot below shows the distribution of temperature anomalies for this pe...

A slow moving precipitation band brought significant rain to the Wasatch Front late last night and early this morning, especially north of Salt Lake City.  Radar imagery below shows the strong returns over the northern Wasatch and lowlands upstream (northern most red rectangle). As of 9:30, Snowbasin-Middle Bowl recorded 0.81" of water equivalent since 4 AM.  And yes, some of that precipitation has fallen as snow on the upper mountain. Ogden airport picked up a half inch, which is a good dousing for the lawns and gardens. Further south, the central Wasatch (southern rectangle) were late to get in on the action.  Alta-Collins has had only .12" of water equivalent since 3 AM, although temperatures are now down to 30ºF, putting that site above the melting layer for now, and they may get a couple more hours of snow.  A little something for the diehards. Meanwhile, in the Salt Lake Valley, the U is up to .27", which should be enough to keep my sprinklers off...

It was an eventful day yesterday with a power outage on campus in the morning, storms in the late afternoon (northern Wasatch Front) and evening (Salt Lake Valley), and more power outages overnight.  The Salt Lake Tribune reports that 85,000 people lost power overnight after a "cascade of outages" struck numerous areas of the Wasatch Front an Tooele.  If high winds were indeed the cause, chalk this one up to cheapness.  Bury those electrical lines and we wouldn't be as vulnerable to these events. Turning from commentary to weather, I mentioned in Wednesday's post that the cold front would tease us Thursday afternoon and then retreat back to the north and the west and that's exactly what has happened.  Check out how the frontal precipitation band pushes into northern Utah, doesn't like what it finds (insert your favorite colorful reason why here), and then decides to tuck tail and move back to the north and west. You don't see that every day and it...

The Storm Prediction Center is giving northern Utah a little love, putting us in the marginal risk category for severe thunderstorms for today and tonight. Source: SPC The impetus for this is the expected late-day increase in thunderstorms near and along the cold front, combined with a deep boundary layer and strong low-level flow that could allow some storms to organize and produce strong to severe wind gusts and hail.  These storm-environment characteristics show up fairly well in the NAM sounding for 2300 UTC (5 PM MDT) this afternoon. A marginal risk means that these severe storms would be limited in organization and longevity, or low in coverage and marginal in intensity.  Thus, not everyone will see a severe storm, but you should keep an eye on the weather.

Trouble is lurking this morning in the form of an upper-level trough that is presently over the northeast Pacific. The latest model runs call for this trough to dig along the Pacific coast and be centered over southern Oregon by 6 PM MDT Friday. The forecast for northern Utah on Thursday is a bit touch-and-go as the cold front ahead of the upper-level trough is expected to push into the northern part of the state.  The latest NAM puts the surface front right at the Salt Lake City airport at 0300 UTC 20 May (9 PM MDT Friday), giving us a chance of some showers and thunderstorms late tomorrow and early tomorrow evening. This is not a simple cold frontal passage, however.  The models tease us with the front late tomorrow and tomorrow evening and then push it back to the north and west.  As a result, during the day on Friday, we're forecast to be in strong southerly flow, which could mean a possible dust event Friday afternoon. All in all, it looks more in...

Source: The Onion "Pseudoscience is a societal mental disease too powerful to be fought in the public arena. The media — the public's main source of information — are more interested in what is popular than what is right. However, behind the relative protection of classroom walls, we have an opportunity to reach the future citizenry and thus a hope that our grandchildren and their children will not succumb to the irrationality that has afflicted our generation." – Sadri Hassani in the May 2016 Physics Today

During the cool season the past few years, it seems like upper-level ridging has been an omnipresent feature over the western United States.  That's not the case at present.  Cooler air and upper-level troughing moved over Utah yesterday and the GFS forecast shows another one moving in right behind it. We may get a break in the action between the troughs, especially if the second one opts to dig down the coast, but for the most part the pattern over the next several days looks springy, with some showers and thunderstorms scattered about.  The NWS forecast summarizes this nicely. No need to panic as there should be periods of dry weather in there with opportunities for outdoor activities, but keep an eye to the sky and adjust plans accordingly. Meanwhile, on the east coast, check out the photo below from Caribou Maine this morning.  They've had 3.5" of snow so far today, the most on record so late in the season. Source: NWS Caribou Forecast Office Re...

Although it fell short of the daily record (89ºF in 2013), today's high of 88ºF was the highest of the calendar year so far. Temperatures were in the 80s beginning just before 11 PM, giving us a day more typical of late June than mid May. Source: MesoWest More seasonable weather returns tomorrow.  Hooray.  I can live without the 80s for a while longer.

Significant upgrades were made by the National Centers for Environmental Prediction (NCEP) to the Global Forecast System (GFS) yesterday.  Perhaps the most significant is a shift from three-dimensional to four-dimensional hybrid ensemble-variational data assimilation.  This, along with other changes to add or improve the assimilation of several satellite and aircraft datasets, should improve the initial analysis.  A complete list of the gory details is available in Technical Implementation Notice 16-11 . In celebration, NOAA issued a slick announcement with some fancy visualization, including the loop below. The meteorological world is waiting, however, to see if these upgrades make the GFS more competitive relative to the ECMWF Integrated Forecast System (IFS, typically called the ECMWF, EC, or Euro). In the future, I'm hoping we will see some significant upgrades to the GFS cloud and precipitation parameterization, which clearly has problems over the mountai...

Yesterday evening, the foothills were so green and the view so spectacular that I could hear Julie Andrews singing "the hills are alive with the sound of music" in my left ear. Regularly spaced deluges have led to a remarkably lush carpet in many areas. But is all this grass a green monster lying in wait?  Each year I see reports on what kind of fire season to expect.  A recent report on Fox-13 called for an average fire season , but what does that mean? Nothing. We are living in a world where the baseline for fire is changing rapidly.  Much of the arid west has and is experiencing rapid development, much of it in the wildland interface.  Our vulnerability has never been higher. Now add the rise in wildfire intensity, which has occurred for many reasons including past wildland management practices, invasive species, disease, and climate change.  With regards to the latter, there is quite a bit of variability from year to year and periods of wet...

Source: Tinelot Wittermans via Wikipedia A student recently alerted me to an article earlier this month in the Washington Post examines plans by the United Arab Emirates (UAE) to build a man-made mountain to "try and maximize rainfall in the country."  The National Center for Atmospheric Research here in the United States is apparently serving as a consultant on the project, evaluating what type of mountain to build. Weather modification is the term given to the alteration of weather by humans.  It can be intentional (e.g., cloud seeding) or inadvertent (e.g., effects of aerosols and land-use changes on precipitation). We are doing both today.  Cloud seeding is intentional, but it really isn't really all that well understood how it works in nature and what the unintended consequences might be.  Modification of local meteorology by cities, especially large ones, is inadvertent but has a robust and clear signal through the urban heat island and changes in prec...

A quick look at the radar loop this morning shows that the Salt Lake Valley will be seeing steady precipitation for most of the morning. A closer look reveals that the broader-scale precipitation shield is moving southward as the echoes move from the northeast.  This is a classic "wrap around" situation in which we receive precipitation being generated in the northeasterly flow behind the upper level low.  Those cells are being generated well above crest level as the flow at mountaintop level shifted to southwesterly overnight. Of one goes up a bit higher, however, to 500 mb (about 18,000 feet above sea level), one finds the magic northeasterlies and the layer where those cells are being generated. One might wonder why with northeasterly flow we're not seeing downsloping and drying on the west side of the Wasatch Range.  The answer is wind shear.  The upper-level flow is northeasterly, but as can be seen in the Ogden Peak time series, the flow at crest...

Although the University of Utah general commencement was last night, most college convocations are today, ensuring that campus is bustling with activity.  The morning dawned, however, with thunderstorms and rain on campus, which surely sent a shiver down the spine of Deans, Administrators, and campus planners. Thunderstorm over the University of Utah campus around 7:05 AM MDT this morning. Radar imagery at 1333 UTC (7:33 AM MDT) showed stronger returns just west of the Wasatch spine east of campus, with two cells further west, including one over campus. These storms were moving northward and as I write this at 7:50 AM MDT, rain has stopped. Graduation day was always stressful for me back in the day.  We used to have our college reception outdoors, and the dean would always want to know if he needed a tent and would call me for a forecast starting days in advance. Today, we have a new building and enough room to hold the reception indoors, so I'm off the hook. ...

There's no better time of year to take advantage of the close proximity of the Avenues foothills than spring.  The hills are green, the mountains are white, and the views simply spectacular.  Yesterday was especially nice with sunny skies and a high of 82ºF.   We're fortunate to have wilderness and the BST at the offing, but development continues below protected areas.   Below is a new McMansion going in just east of Ensign Peak.  I'm no geologist, but I'm not sure this is the best place to build a house given the rocks and boulders that have calved off the cliffs above.  Society exists by geologic consent, subject to change without notice. It always amazes me how much aspect affects the ecology in Utah.  As arid as the south aspects are, it's pretty lush still on north aspects.  Last week the flowers were in bloom here too, but they are past peak now. Graduation celebrations and ceremonies here at the U are today and tomorrow. ...