Wasatch Weather Weenies

Before talking about the the potential for snow the next few days, I'd like to remind everyone that this blog isn't a forecast service and many days we don't discuss the forecast.  Thus, if you need a forecast for the Wasatch, you can always check out www.utahskiweather.com , run by some really talented students here at the U. Now that's out of the way, let's talk briefly about the next few days.  Everyone is salivating for powder, but we're not going to be seeing any.  We have two quick hitting storms moving through.  The first is tonight: And the second is Sunday night: The storms are going to be wet and sloppy.  In the Cottonwoods, snow levels in each storm will start out in each storm near 8000 ft.  Temperatures and snow levels fall during each storm, but only marginally.  Accumulations below 8000 ft are likely to be minimal.  Above that level, the snow is going to be a high density variety.  Given the quick hitting nature ...

Some spectacular clouds could be found over the Salt Lake Valley this morning.  First, we have a marvelous example of an orographic cloud over Lone Peak.  It's been sitting there since yesterday and is produced by southerly and southwesterly flow being forced up and over Lone Peak and the high divide that separates Little Cottonwood and American Fork Canyons. Even better are examples of Kelvin Helmholtz Billows , referred to by meteorologists as simply KH.  KH billows look like waves breaking on the beach. Photo: Peter Veals Water waves break because friction slows the wave more at the ocean floor than near the ocean surface.  This causes the wave to steepen and eventually break. KH waves in the atmosphere are produced by strong vertical wind shear.  In the photo above, the flow at the top of the wave is stronger than the flow at the bottom.  This leads to wave breaking much like occurs in the ocean.  Note that wave breaking is evident in ...

From the Weather Channel today, an article entitled "Mt. Shasta: Is U.S. Snowstorm Record in Jeopardy? To quote the article , "The Thursday morning National Weather Service summit forecast for Shasta predicted an incredible 33 to 39 inches of snow -- just for Thursday alone...Add up the high end of the numbers and you get a forecast maximum of 218 inches of snow in four days! " Unfortunately, this is an example of extrapolation and sensationalism run amok.  The world record single snowstorm accumulation of 189 inches was set from Feb 13-19, 1959 at Mount Shasta ski bowl. The ski bowl is going to get a pounding over the next few days, but some of the precipitation is going to fall as rain.  Snow levels are quite high in this storm.  Here's what the base looked like at noon today. What about higher up on the mountain?  Well, the 218 inch figure noted above is for the summit.  Surely it will snow a ton there?   Unfortunately, precipita...

During inversions, meteorologists frequently call the airmass beneath an inversion a cold pool .  The name seems appropriate as the dense air, when it is full of pollution or topped by clouds, behaves in much the same way as a pool of water. In some instances, however, the cold pool is incredibly shallow.  As such, it might be better labeled a cold puddle.   One could observe lingering pollution in such a cold puddle yesterday afternoon over the Great Salt Lake and and lower elevations of the northern Salt Lake Valley. Pollution in an extremely shallow cold pool (a.k.a. cold puddle) over the Great Salt Lake and lower elevations of the northern Salt Lake Valley at about 5 PM MST 28 Nov 2012 (click to enlarge) That cold puddle represents the last remnants of our latest inversion event, which was extremely persistent over the Great Salt Lake.  One can see the cold puddle pretty well in the surface analysis from 5 PM MST yesterday.  Check out the...

Looking out over the northern Salt Lake Valley and southern Great Salt Lake from the Avenues Foothills yesterday @ 430 PM MST Although the past few days seem pretty boring weather wise, they are simply fascinating for a micrometeorologist.  The contrasts in surface temperatures in northern Utah have been astounding.  Let's take yesterday afternoon as an example. At 2200 UTC (300 PM MST), it was a balmy 56ºF on the University of Utah campus and 58ºF just up the hill at the Utah Museum of Natural History.  However, at the Salt Lake City International Airport, which is about 500 feet lower, it was only 50–52ºF. Source: MesoWest This reflects the incredibly shallow nature of the inversion.  However, it gets even more interesting if you look out over the Tooele Valley where temperatures were only in the 40s.  During many inversions, especially those without snowcover, afternoon temperatures over the lake are often much colder than those over the surround...

How many of you scientists out there can say that it is a Hollywood starlet's lifelong dream to do your job?  Scarlett Johansson fulfilled that dream this morning when she did the weather on the Today show. Of course, most meteorologists don't work in television broadcasting, and most television weather reporters aren't meteorologists (Al Roker's degree appears to be in Communications), so ScarJo isn't really doing what most meteorologists do.  Nevertheless, we're more than happy to be so appealing to  one of the 100 sexiests actresses of all time .  Perhaps Channing Tatum will have a go next.

Source: foodiesteve.wordpress.com Not much has changed.  The pre-thanksgiving forecast was a turkey, and so is the post-thanksgiving forecast. The GFS still calls for the storm track to remain to our north.  Here's the accumulated precipitation for the 192-hour period ending at 0600 UTC 4 December.  Depressing.  We get just a couple of weak brush-by systems. Source: NOAA/NCEP The European Center forecast is a bit more optimistic as it sags the jet a bit further south.  Thus, it's a bit wetter, with a system coming through Friday and Saturday.  Let's hope so.  We could use the snow.  A dietary change is desperately needed.

Source: http://davidlansing.com The prospects for a deep-powder day for the holiday weekend are not zero, but are fairly low.  The latest computer model forecasts keep the action largely to our north.  The total accumulated precipitation forecast by the GFS between 1200 UTC this morning and 2100 UTC Sunday afternoon shows heavy precipitation over the northwest, and dry conditions over the southwest.  The Wasatch sit just to the south of the goods. Source: NOAA/NCEP Two weak systems graze northern Utah during this period, one Wednesday night, the other late Saturday and Sunday.  We'll have to hope these storms are more productive than currently forecast if we're to get a good freshening up during the holiday weekend.  Yes, it's a turkey of a forecast, but there is something to be thankful for.  The snowpack SWE at Snowbird is 140% of average.  At upper-elevations in the central Wasatch, we will have an above average snowpack for this time of...

It goes without saying that altitude can be a blessing, especially during a warm period in the shoulder season.  While the higher elevations of the Wasatch picked up a gain in snowpack this weekend, the lower elevations, specifically those below the snow line, suffered. John Paul Gondola Base (8800 ft) Strawberry Gondola Base (6800 ft) What a shame to lose all that natural low-elevation snow in the northern Wasatch from a couple of weeks ago. While this event is simply the result of a relatively warm period and storm, it does provide a glimpse of what we will likely see more of in the coming decades—a greater fraction of precipitation falling as rain at the lower elevations, where the snowpack will also see more frequent cool-season melt events ( several studies suggest this is already happening ).  On the other hand, the upper-elevations have some insurance against the initial wave of warming given their colder temperatures.  Thus, the contrast between the lo...

Early morning snow at Alta Last weekend's lake-effect snow was relatively low density, and thus underwent substantial settlement and compaction this week.  The Alta-Collins 7 am snow depth dropped from a maximum of 42 inches on October 11 to a minimum of 24 inches yesterday. Notice, however, the uptick to 29 inches this morning.  The dribs and drabs of wet snow yesterday and overnight are adding up.  And it is high density base builder.  Over the past 24 hours, Alta-Collins has observed 8 inches of snow with 1.16 inches of SWE.  That's 14.5% water content.  The Utah Avalanche Center suggests the storm is producing quite a bit of graupel.  If it's white, it's good, and if it's graupel, better yet.

Looking for a way to blow some time at work today?  Peruse the National Climatic Data Center interactive map for record 1-, 2-, and 3-day snowfall by station . Yup, this is it.  The history of record snowfalls at your fingertips.  Alta's records for 1-, 2-, and 3-day snowfalls are 34, 52, and 70 inches respectively.  Highmarket, NY on the Tug Hill Plateau east of Lake Ontario can top that with 43.5, 63.8, and 84.2 inches.  And of course, there is Thompson Pass, Alaska, with 62, 120.6, and 147 inches.  That's crazy! A few caveats.  This map is based solely on data provided by National Weather Service cooperative observers.  Snow depth is typically measured once a day at the same time each day.  Thus, these are daily and not 24-hour records.  Alta's 24-hour record is 55.5 inches.  I suspect that storm cross the daily measurement time and thus was split into two days (I suspect the measurement wasn't made by the cooperative obse...

Early season snow is of course a blessing for the mountains, but it can be a curse here in the valley. Valley snow leads to stronger and more persistent cold pools (a.k.a. inversions).  The buildup of pollution over the past couple of days is quite evident looking south over the Salt Lake Valley this morning. The morning sounding from the Salt Lake City airport shows a stable, near isothermal (i.e., constant temperature) airmass extends from the valley floor to about 750 mb, or about 1000 m above the valley floor.  We're pretty much cutoff from the clean air above. Source: NOAA/NWS/SPC Fortunately this will be a short-lived event as the flow aloft is expected to increase tonight and will probably be strong enough tomorrow to at least stir things up and keep the pollution levels from getting annoyingly high.

Source: BizarroComics.com The borderline El Nino event that was thought to be a possibility a couple of months ago (see Oct 5 and Sep 12 posts) appears to be toast.  The Climate Prediction Center officially cancelled the El Nino watch last week and expects ENSO-neutral conditions through the winter.  In other words, this is likely to be a No Nino winter.  Click here for the gory details. And thank goodness for that, not because it means anything in terms of what to expect this winter , but because I won't have to hear people mindlessly blaming every weather event on El Nino.  I guess now they can blame it on the absence of El Nino.

The New York Times recently published a couple of interesting articles in the wake of superfrankenstorm Sandy.  The first is related to the disaster-preparedness economy, or what the author appropriately calls Mad Max Capitalism (article access here ). The bottom line is that there is big money in disaster preparedness, and this is a growing segment of the economy.  My bet is that they will sell millions of generators in the NY metropolitan area in the coming years.  One of the people interviewed is from The Ready Store, which is based in Draper, Utah.  One of you enterprising meteorology students ought to give them a heads up before the next big storm. The second discusses a neighborhood on Staten Island where there were unfortunately several fatalities (available here ).  Relevant is how residents were lulled into complacency by false alarms or past storms that were not all that severe.  This is one of the challenges facing meteorologists and emer...

We just received this morning's visible satellite image from MODIS.  This is the first visible image since the storm and, although there are some high clouds, they are thin enough that you really can't miss where it snowed and where it didn't.  Check out the lack of snow cover north of Utah Lake around Saratoga Springs and American Fork.

I thought I'd spend a moment today to put the weekend storm into a climatological context, especially the lake-effect phase.  To do this, I'll be concentrating on data collected by the NRCS SNOTEL stations located at mid mountain at Snowbird.  Based on the climatology developed by Yeager et al. (2012, in press, but available here ), this site receives more lake-effect precipitation than any other regularly reporting site in northern Utah (Note: Alta might receive more, but we lack the data to verify this, and there is a site in the northern Oquirrhs that is a very close second).  In addition, during the weekend storm, the Snowbird SNOTEL received more lake-effect precipitation than any other SNOTEL, although Parleys Summit was a close second.  As can be seen in the meteogram below, there were two major phases of precipitation during the storm.  The first was during the cold frontal passage on Friday.  The second was during the lake-effect period, which b...

As reported to the National Weather Service.  Totals through time indicated. Snowbird: 46" (8 am Sunday) Alta: 45" (6 am Sunday) Alta-Collins: 42" (8 am Sunday) Spruces: 35" (6 am Sunday) Bountiful Bench: 28.5" (9am Sunday) Cottonwood Heights: 25" (7 am Sunday) Upper Millcreek: 24.5" (8 am Sunday) Sandy (4852 ft): 22.7" (7 am Sunday) Centerville: 18.2" (7 am Sunday) Upper Avenues: 17" (7 am Sunday) I suspect many of these are settled snow depth measurements (I have 15" at my house at 4800 ft in the Avenues).  Measurements taken every 24 or 12 hours and added would be larger.  These totals include snow from the frontal portion of the event on Friday.

As noted in the previous post, this lake-effect storm is one of the best of the last 15 years or so, and it continues this morning. Data from Alta-Collins shows quite well how the lake effect intensified each of the last two nights, as is common with the Great Salt Lake effect.  Note the ramp up in precipitation rate, with a peak Saturday morning and then another peak on Sunday. Source: NWS The automated snow-depth sensor at Alta-Collins busted through the 40" mark this morning.  I always consider that to be the start of decent early season skiing (my standards are high).  It's tough to say whether or not we'll be able to hang above 40" once things start to settle after the storm, but this is a really good start regardless. We are going to continue to see lake-effect this morning.  The storm will wind down after noon.  There should be some great views once the clouds start to break up.  Enjoy!

Wow, what an event.  After a bit of an afternoon lull, the lake-effect is raging once again. Source: NCAR/RAL We are now up to 1.1" (28 mm) of SWE at the Snowbird Snotel since 0700 UTC 10 Nov, when this lake-effect period began.  For the 1998–2009 period examined by Yeager et al. (2012), there were only a handful of lake-effect periods that produced more precipitation. SWE produced at he Snowbird SNOTEL during lake-effect periods 1998–2009 Source: Yeager et al. (2012) We have a long ways to go to get into the top three, but we are now in the top five.  Valley accumulations are also impressive.  It is spectacularly beautiful with the dendrites stacked deep in the Salt Lake Valley.  

The lake-effect event continues to rage.  This morning, the event has slowly transitioned into a more banded structure, as is now apparent in the radar image below. We don't really understand these structural transitions, but I think in this case it might be related to a gradual veering of the large scale flow at ~700 mb (roughtly crest level) from westerly to northwesterly.     This means the large-scale flow is transitioning from primarily across the surface convergence zone (see previous posts) to along it. I really should be skiing.

Non-banded lake-effect events don't get much better than this one.  What a beautiful radar loop below. Can it hang on?  Let's hope so.  Looks like heavy precipitation now from Little Cottonwood through the Bountiful area mountains.  It appears that Alta-Collins is getting creamed with very high snowfall rates.  The automated total snow depth is squirrelly, but if you ignore the false 240 numbers, it looks like they got 10" since 4 am.  The interval board was wiped twice during this period.  Looks like 10" through yesterday afternoon, then 13" through 9 am this morning, then another 3" as of 10 am.  Yes! My impression is that this is one of the better lake-effect events we have had in some time, and it ain't over yet.

Overnight we had a nice transition to lake-effect snow, which has been concentrated over the northern Wasatch Front and eastern Salt Lake County. 0707–1454 UTC 10 Nov 2012 KMTX Radar Loop  As can be seen in the loop above, the event thus far has been what we call "non banded" in that there is a broad area of lake-effect precipitation rather than a narrow, isolated band. MesoWest observations show what we often see during lake-effect events with strong westerly flow over the western half of the Great Salt Lake converging with a stagnant and cooler airmass along the Wasatch Front and over the eastern half of the Great Salt Lake. This convergence serves as the trigger for lake-effect convection, with precipitation falling downstream to the east and southeast. During the October lake-effect event, we discussed how lake effect tends to weaken during the day (click here ).  This effect is greatest in the fall and spring and weakest during the winter.  It will be ...

This has been a very impressive precipitation event thusfar in the Salt Lake Valley.  As of 2 PM MST, 0.94 inches of precipitation (snow-water equivalent) has fallen at the Salt Lake Airport. Most skiers typically expect that when it snows this much in the valley, it must be snowing a lot more in the mountains, but that is simply not the case so far today.  On average during the month of November, Alta receives about 5 times as much precipitation as the Salt Lake City airport, but that's the average.  Today, we're seeing very limited orographic enhancement  of precipitation.  For example, Alta-Collins has received only 1.17 inches of precipitation (snow-water equivalent) thusfar, or only 1.25 times more than Salt Lake City Airport. Why is the enhancement so small?  It's because the precipitation is being generated primarily by the front and typically the orographic enhancement of precipitation is smallest over the Wasatch Mountains during periods when l...

I love it when a front decides to linger over the Wasatch Front.  Below you can see it slowly moving through northern Utah over the past several hours. Looks like snow will continue for the better part of the day in the valley and mountains.  6 inches and counting in upper Little Cottonwood as I write this.

A strong cold front passed through Salt Lake City at about 4 am MST this morning, as clearly shown by the meteogram from the Salt Lake International Airport. Such a large and dramatic temperature fall is somewhat unusual in the early morning hours, but with strong prefrontal winds, there was little cooling at the surface overnight, so the full brunt of the front could be felt at the surface. Winter arrived with a bang following the frontal passage as thunderrain turned to thundersnow with falling temperatures at the airport between about 6 and 7 am MST. It will be interesting to see how much accumulates today in the Salt Lake Valley.  Temperatures are right at the margins for snow and the ground is very warm.  There should be dramatic contrasts in accumulations between the valley floor and the upper benches, and from surface to surface. BTW, the leading edge of the front was very shallow.  At 7am it was 34ºF at the Salt Lake Airport, but still 31ºF at Alt...

We have an exciting stretch of weather ahead and it starts today with an Intermountain cyclogenesis event. Cyclogenesis is the formation and development of a cyclone, known colloquially as a low pressure system.  Today we have a nice example of this happening over the Intermountain West.  Watch in the loop below, which includes both analyses from yesterday and last night and forecasts for today, how a cyclone digs southward along the Pacific Coast and decays as a new cyclone forms over the Intermountain West. This sort of behavior is not uncommon in areas of complex terrain.  Cyclones have a difficult time penetrating through areas of high topography.  As a result, they often decay as they approach a mountain range (in this case, the Cascades and coastal mountains of the Pacific Northwest) and reform in the lee.  The Intermountain West is a favored region for cyclone formation because it lies downstream of the Sierra Nevada and Cascade Ranges. Also cont...