Wasatch Weather Weenies

It's not easy to perform a surface frontal analysis tonight.  There are two fairly well defined boundaries, I'll call them frontal fragments , evident in the MesoWest data.  The first is in southwestern Wyoming there there is a wind shift and collocated 10-12F temperature contrast just west of Green River.  This is the likely position of the Arctic front that will push into northern Utah from the east late tonight. The second is over the Snake River Plain just east of Twin Falls where there is also a wind shift.  The baroclinity here is a bit more broad, with temperatures decreasing from about 30F near the front to the single digits in the upper Snake River Plain. In contrast, it is very difficult to nail down a wind shift or front in the intervening highlands.  The flow is almost exclusively from the northern half of the compass and finding the leading edge of the cold air is very difficult.  Although Arctic air is leaking into this region, there is n...

The latest 1.3 km WRF forecast is in (initialized using the 6-h GFS forecast for 1800 UTC 31 Jan), which includes a forecast projection through tomorrow evening.  It produces a broad region of downslope winds along the northern Wasatch tomorrow afternoon and evening with sustained winds between 30 and 40 knots. Note that the center of action has shifted southward from the earlier WRF simulation.  The strong winds downstream of the Cottonwoods seem odd.  That is an unusual place for downslope winds.  Perhaps this reflects the lower height of the model topography.  It's also a bit unusual for the downslope flow to be strongest in the afternoon, although this time of year the solar forcing is fairly weak, so that might reduce the diurnal variability. As previously mentioned, we've never used this model before to examine downslope winds, and it is unclear if reliance on a single high-resolution model might lead to serious "crash and burn," so it will be intere...

This morning's (1200 UTC) initialized NAM forecasts the movement of a back-door Arctic front from Wyoming into Utah and across the northern Wasatch Mountains at about 1200 UTC (0500 MST) tomorrow (Tuesday) morning.  I refer to this as a back-door Arctic front because it is approaching from the east.  Below are three perspectives of the NAM-forecast back-door Arctic Front as it moves into the Wasatch Front. NAM 2-m temperature (color fill every 2C) and 10-m wind (full and half barb denote 5 and 2.5 m/s, respectively) valid 1200 UTC 1 Feb 2011 Perspective view with potential temperature cross section (white) More oblique perspective showing potential temperature "wall" with arctic front merged with mountain wave induced by the Wasatch Mountains I suspect tomorrow and possibly Wednesday are going to be a brutally cold area along portions of the east bench from Parley's canyon north.  Not only are we dealing with very cold air, but easterly flow, a strong ...

Enjoy the relatively balmy conditions while they last.  MesoWest observations today are simply fascinating and show cold air approaching northern Utah from both the north and the east. In extreme northeast Idaho, northeasterly flow is pulling cold air across the continental divide and into the upper Snake River Plain.  At Island Park, temperatures have fallen from a high of 43F yesterday afternoon to a minimum of -5F this morning (although they have since rebounded to 3F). Meanwhile, cold air is moving westward across Wyoming toward Evanston through the low elevation basin between the Uinta and Wind River Mountains.  Rock Springs has remained solidly at 10F all day today. Thus, cold air will be approaching Utah from two directions.  There is nowhere to hide!

Glasgow, MT

The latest surface observations show a balmy 30F here in Salt Lake, but 10F in Rock Springs, -6 in Cody, and a nasty -24F in Great Falls. MesoWest surface observations at ~1600 UTC (0900 MST) 31 Jan 2011 At Rock Springs, winds shifted from westerly to east-northeasterly between 4 and 5 AM MST.  Temperatures began to fall ahead of this wind shift, but dropped more quickly following it.  Thus, I suspect it represents the leading edge of the arctic air. Change is most certainly on the way...

So much to talk about today and so little time!  An exciting week of weather is forthcoming, and I'm looking forward to it. As we discussed in the previous post, the models are forecasting a serious blast of cold air to move into Utah this week, with the arctic air arriving Monday night and Tuesday. The 12Z initialized NAM from this morning (Sunday) drops Salt Lake's 700-mb temperatures down to a brutal -23C by Tuesday afternoon.  There are not many days around here where the 700-mb temperature is that low. This morning's 0900 UTC initialized SREF is event colder with a forecast ensemble mean 700-mb temperature for KSLC of -25C. The GFS remains the "warmer" model, with a forecast 700-mb temperature of -22C.  Warm here is clearly a relative term! The setup for the arctic blast involves interactions between large-scale features in the high latitudes and the mid-latitude Pacific Ocean.  In the high latitudes, a deep low is presently centered near Hudson ...

The NAM forecast initialized at 1800 UTC 29 Jan (Saturday) has an impressive blast of cold air coming into Utah.  As discussed in October , the 700-mb temperature at Salt Lake City is usually between -20C and 20C, so I use -20C at 700 mb as an indicator of "really cold air."  The 84 hour forecast has sub -20C air covering much of the state of Utah, including about -21C at KSLC.  BRRRR!!!! On the other hand, the GFS forecast initialized at the same time has a somewhat different solution.  The coldest 700-mb air comes through 12-h earlier, at 1800 UTC 1 Feb, with the 700-mb temperatures at KSLC only falling to -19C.  Cold, but not as far out the tail of the bell curve. Given the differences between the NAM and the GFS, I thought I would also consult the NCEP Short-Range Ensemble Forecast system (SREF).  As I understand it, the SREF is comprised of 21 forecasts produced by four different modeling systems run with differing initial conditions.  For t...

Somewhat related to the previous post , recent changes in the Arctic the past few years are quite remarkable. NOAA has developed a nice web site called the Arctic Report Card for tracking environmental change in the Arctic.  The YouTube video below provides a nice summary, although the hypothesized linkage between recent sea-ice loss and cold waves over North America and Europe is a subject of ongoing investigation.

I've been holed up all week at the American Meteorological Society Annual Meeting in Seattle.  I've attended a couple of interesting talks on climate change and communication, including one by Richard Sommerville in which he conducted an interesting thought experiment that went something like this. Imagine you are living on a planet that is exactly like Earth, including the rate of fossil fuel consumption that has occurred since the industrial revolution.  What is different on this "Planet B" is that there are no weather observations for examining past and recent climate change, no satellite observations for observing sea level rise, sea-surface temperatures, and ice-sheet changes, and no supercomputers and Earth Systems models for understanding and attributing past climate change. Planet B...almost the same as Earth The citizens on such a planet would have no idea that the planet is warming, that the arctic is becoming ice free, that the Greenland ice sheet is...

In the previous post  examining the best colleges for winter sports enthusiasts, I opined that " t he University of Utah is hands down the best University/College on the planet for winter sports enthusiasts ."  I also offered up a couple winter-sports worthy colleges/universities that were not included on the US News and World Report list . I've thought of some additional North American institutions that warrant mention.  They are: University of Vermont .  It's really quite shocking this wasn't on the list as Burlington sits at the best intersection of mountains and snow in the eastern United States. University of British Columbia .  Granted the skiing right in Vancouver isn't great, but you can ski on the edge of town and Whistler/Blackcomb and numerous backcountry adventures are within easy striking distance.   Western Washington University .  Also within striking distance of Whistler/Blackcomb, Mount Baker, and incredible backcountry skiing. ...

An article in today's Daily Utah Chronicle reports that the U has made the list of Best Colleges for Winter Enthusiasts from U.S. News and World Report magazine . Let's be real.   The University of Utah is hands down the best University/College on the planet for winter sports enthusiasts .   It isn't even close.  Where else in the world can you get a low-cost, world-class education and ski or snowboard some of the best terrain and snow on Earth just minutes from your dorm room? The start of this backcountry ski tour is 20 minutes from the U.  Eat your heart out CU-types. The other schools on the U.S. News and World Report list: University of Colorado-Boulder .  The article touts the "short driving distance" to Vail and Winter Park.  Apparently the author hasn't spent hours sitting in traffic on I-70 during one of Colorado's rare deep powder days.  How rare are those deep powder days?  Berthoud Pass near Winter Park, one of the snowiest ...

Bears, Packers, Jets, Steelers.  It's hard to imagine a better matchup of black-and-blue-type football teams than that (although the AFL-derived Jets might not be a classic old school team, they have the attitude). I'm especially pleased to see it is going to be well below freezing for both the NFC and AFC championship games.  Championship football should be cold and a cold anticyclone is in firm control over the eastern United States. The current (0900 MST) temperature in Chicago (1300 MST kickoff) is an unlucky 13F, with a forecast high of 18F. Further east, in Pittsburgh, the current temperature is also an unlucky 13F, with a forecast high of 16F. Kickoff, however, is at 1630 MST, after sunset, so it's going to be colder during the game.  BRRRR.  Fair conditions should prevail at both locations, so a snow bowl scenario is unlikely.  Nevertheless, I'll be happy to watch these games from a warm bar with a cold beer in hand.   This is of course...

Something different for your reading pleasure today.  Having formerly skied a lot in the Pacific Northwest, I've had a few encounters with tree wells from hell.  Little did I know there was an entire web site devoted to the topic. A tree well is an area around the base of a tree where the snow is poorly consolidated.  A fall into one of these wells can be extremely treacherous, especially if you are alone, as it is very difficult to extract yourself without the help of a partner.  A head first fall into a tree well can result in death from suffocation.  This sounds like an urban myth, but it is not.   Have a look at the Tree Well and Deep Snow Safety web site for more information.

What may be the biggest most persistent, high-amplitude, upper-level ridge of the winter is about to build over the western United States.  The good news is that it will be preceded by yet another short-wave trough embedded in northwesterly flow, which should give the Wasatch Mountains another quick hitting storm late tonight and early Saturday. 0600 UTC 21 Jan GFS Forecast Valid 1800 UTC (1100 MST) 22 Jan 2011 That storm will be our last major shot of snow for at least several days, so it is imperative to "ski now, work later."  After that, we'll likely be high and dry as we won't be in a dirty ridge situation like we've had for the past week.  This ridge is very high amplitude.  We will, however, have great weather for long adventure tours and for skiing fast corduroy in the warm sun at the resorts. 0600 UTC 21 Jan GFS Forecast Valid 0600 UTC 27 Jan 2011 Don't forget to wear your sunscreen!

There are probably as many definitions of front as there are meteorologists and, if there is something that meteorologists love to argue about, it is surface frontal analysis. Mother nature does not think in terms of fronts.  She thinks in terms of fundamental physical processes.  Those processes frequently produce strong temperature gradients or, what humans, for the sake of convenience, call and frequently analyze as a front.  However, the magnitude of temperature gradient (or temperature contrast) required for the existence of a front remains subject to debate and frequently the position of a front on a surface weather map is ambiguous.   The classic example is a composite of the fronts and troughs analyzed by the participants of a workshop convened at the National Meteorological Center (NMC, now the National Centers for Environmental Prediction, NCEP) and published in Uccellini et al (1992) and Sanders and Doswell (1995) .  Note the lack of agreement with...

Great discussion of a monster cyclone over the North Pacific on the Cliff Mass Weather Blog.  Central pressure of 933 mb!   Have a look .

What Mother Nature giveth, Mother Nature taketh away.  Our run of quality ski conditions and low-moderate avalanche hazard, extending all the way back to early November, ended this weekend.  Ski conditions on the Wasatch Back were said to be like "eastern skiing."   My experience in Little Cottonwood on Sunday was more like something from the Pacific Northwest, but I didn't bother going out on Monday to see if the snow conditions had degraded further.  Evelyn Lees' Salt Lake Avalanche Advisory suggests that the ski conditions are currently something that only a seasoned New Hampshire skier could love: "Our rain saturated snow-scape is something else…there are smooth, ice rink rain crusts at the upper elevations, with some surprisingly decent turns on lower angle slopes where an inch or so of graupel stuck onto the ice. But, sharpen your edges and glue in your dentures for the sections of wind scoured bare ice sheets and rough frozen crusts at the mid and low e...

I may have spoken a little too quickly about the demise of the cold pool .  It appears there still are a few cold-pool fragments persisting around the area.  For example, check out the observations near Lehi, Point of the Mountain, Bluffdale, and Riverton where temperatures range from 39-47F. Check out the temperature variability at the glider port near point of the mountain, which suggests it sits right near the top of the cold-air pool with the cold air intermittently spilling over the observing site. Finally, haze and smog within the cold-pool fragment can be seen when looking south from the Avenues.  In particular, check out the visibility obscuration in the saddle of the Traverse Mountains. Further evidence of the value of MesoWest.

It is remarkably warm in the Salt Lake Valley today.  As of noon, we've hit the big 50 here at the University of Utah and several locations in the Salt Lake Valley are reporting temperatures in the low 50s. This morning's sounding showed a strong inversion and surface-based cold pool persisting in the lowest elevations near the Great Salt Lake, but I think we have finally scrubbed out most (but perhaps not all) of the cold pool.  In particular, temperatures at KSLC airport have climbed to 49F (10C), which gets us close to a total mixout, and Hat Island is even 47F. This is a welcome change from the dreary gloom of the persistent cold pools that have been in place over the past few weeks.  On the other hand, the rain, wind, and warm temperatures have largely trashed the skiing.

Cup and windmill anemometers are frequently used for remote observations in mountainous regions, including the Wasatch of Utah. Automated weather station with cup and vane anemometer on top. Photo: Walter Siegmund and Wikipedia Commons Windmill Anemometer.  Courtesy NOAA/NSSL and Wikipedia Commons Both are vulnerable, however, to heavy riming, which prevents the movement of the cups, windmill, and/or vane.  Such riming occurs frequently in maritime mountain ranges, but is less common in Utah. The warm storm last night, however, appears to have led to heavy riming and the failure of the wind sensor at Cardiff Peak.  The tell-tale sign of riming is a rapid, unnatural drop in wind speed to zero, and this is what happened at Cardiff Peak between midnight and 1 am MST last night. Given that the wind direction changes some after 1 AM, it could be that the cups or windmill are not rotating, but the vane is able to move some.  Of course, there's also the ...

As advertised a couple of days ago, snow levels have climbed today and as of about 2PM this afternoon sit somewhere near 8500 feet.  The Alta cam photo from this morning summarizes the day nicely. I'm now ready to "officially" declare that  this dirty ridge has reached at least NC-17 status .  I've skied some warm storms at Alta, including some with serious Cascade concrete, but don't recall ever squeezing as much water out of my gloves as I did at the end of the day today.  Dirty indeed! Skiing at Alta today, I found the "wintery mix" of ice pellets, mist, and drizzle to be quite interesting.  Even above the freezing level, which as of 2 PM sat at about 9500 feet, I was constantly wiping my goggles to see.   The existence of liquid water above the freezing level is not uncommon in warm, shallow clouds like todays, but there were also plenty of ice pellets around and very few snowflakes.  This is speculation, but I suspect that today the...

Today's maximum temperature of 45F at the University of Utah looks to be the the highest temperature observed on campus since December 18. As is often the case during winter when snow is present, we have either been in cold post-frontal air or mired in a valley cold pool for quite a while.  It's great to break 40 and see my driveway free of snow! In contrast, temperatures on Mt. Baldy have peaked above today's maximum of 23F on six calendar days since December 18.  Note that at this high altitude location, the maximum temperature is not always in the afternoon. This crudely illustrates how decoupled conditions in the valley can be from the free atmosphere.  Further evidence why it would be good to understand the contribution of cold pools to long-term climate trends over Utah.

As discussed in an earlier post , we're presently under the influence of a "dirty ridge," a long-wave ridge with relatively low amplitude that allows moisture and upper-level troughs to spill over it so that we still see periods of clouds and snow. For the most part, this is good news as the Wasatch desperately need a freshening up, but I'm thinking about upping the rating for this dirty ridge to NC-17 or even XXX.  Why?  Well, the latest NAM is bringing in periods of precipitation beginning on Sunday, but with 700 mb temperatures rising to near 0C by Sunday evening. 1800 UTC 14 Jan 2011 Initialized NAM Forecast Valid 1500 UTC 16 Jan 2011 (8 AM MST Sunday) 1800 UTC 14 Jan 2011 Initialized NAM Forecast Valid 0300 UTC 17 Jan 2011 (8 PM MST Sunday) So, in the heart of January, the climatologically coldest time of the year in Utah, we are going to see a warm storm, with snow levels Sunday evening near or even above 8000 feet.

As discussed in yesterday's post examining global temperatures , the National Climatic Data Center has released its preliminary year-to-date global, national, and statewide climate summary for 2010. If you thought this was a relatively cool year in Utah, you are right, but only in terms of the recent climate.  The statewide average temperature for Utah in 2010 was 48.9F.  This makes it the second coolest year (after 2009) since 1993, so it certainly seemed cool for recent Utah transplants or native Utahns who are short in the tooth.  Those with a longer memory might have a different perspective as 2010 was still a full degree warmer than the long term average for the 20th century (47.9F). Graph: NOAA/NCDC In fact, Utah has not had a year with an average temperature below the 20th century mean since 1993.  There are ups and downs from year to year, but the dice are loaded for warmer years. One thing I would like to see done with the Utah temperature reco...