Tomorrow Will be Deep

Since last night we’ve been experiencing strong southwest winds and rounds of heavy precipitation out ahead of an approaching strong cold front. In a couple hours (around 8PM) the front will swing through. Several hours of very heavy snowfall, strong winds, and dropping temperatures will accompany it. Snow levels will drop to the valley floors as winds swift from south west to north west. Travel through mountain passes will become extremely treacherous. Output from the HRRR depicts this frontal passage well:

hrrr_ref_frzn_swus_fh1-18

The intensity of the snowfall will begin to decrease overnight, but on and off snow showers should continue in the mountains through midday tomorrow during a period of moist NW flow.

So far most resorts have picked up anywhere between 10 and 15 inches. Through midday tomorrow I expect another 15 to 20 inches, bringing totals to 2-3 feet.

The skiing should be awesome in the mountains MLK weekend. Saturday will be generally clear (maybe a snow shower or two in the mountains) and Sunday will be mild with increasing clouds out ahead of our next storm system.

The next system will enter the region Sunday night and last through the day on Monday. Right now it looks like a moderate event. The NAEFS below shows there still decent uncertainty regarding the size of this system.

NAEFSPL_CLN2019011712F168

Beyond Monday’s system, another one may impact the region midweek. More details will be provided on these systems in upcoming posts. Enjoy the powder!

On to Phase Two

TLDR: The current lull in activity will give way to a rather exciting burst of energy Thursday evening into Friday morning in which very large mountain snowfall totals are expected. Quiet weather for the weekend before another system comes through Monday; active period continues through (at least) next week.

Summary of previous system:

A short wave trough came through our area last night into this morning, bringing with it modest amounts of snow at the ski resorts. Below is an image showing the snow totals for several resorts in northern Utah. Alta and Snowbird were the big winners last night/this morning with 10+ inches of snow. So far, though, Brighton has reported the most amount of snow for the season, hauling in 227 inches (almost 19 feet of snow!).

Snow totals for the past 24 hours at several northern Utah resorts. Also shown are season snowfall totals for these resorts.
Snow totals for the past 24 hours at several northern Utah resorts. Also shown on the right are reported season snowfall totals. Totals taken from individual resort snow reports on their websites: http://www.powdermountain.com/en/resort-conditions, https://www.snowbasin.com/the-mountain/conditions, https://www.parkcitymountain.com/the-mountain/mountain-conditions/snow-and-weather-report.aspx, http://www.deervalley.com/OnTheMountain/Mountain, https://solitudemountain.com/on-the-mountain, https://www.brightonresort.com/mountain/snow-report, https://www.alta.com/conditions/daily-mountain-report/snow-report, https://www.snowbird.com/mountain-report

 

Avalanche Watch:

Take note! There is an Avalanche Watch for the Wasatch (and Uinta Mountains) from now through 6 AM Thursday! Be very careful in the backcountry. From the National Weather Service in Salt Lake City:

RECENT SNOW COMBINED WITH HEAVY SNOW TOMORROW
  WILL LIKELY CREATE WIDESPREAD AREAS OF UNSTABLE SNOW AND
  DANGEROUS AVALANCHE CONDITIONS. BOTH HUMAN TRIGGERED AND NATURAL
  AVALANCHES WILL BE LIKELY. STAY OFF OF AND OUT FROM UNDER SLOPES
  STEEPER THAN 30 DEGREES

Current Conditions:

We are in a bit of a lull in precipitation as the short wave trough that passed through last night and this morning has given way to a short wave ridge. In fact, throughout the afternoon we have seen a pretty rapid increase in temperatures. All of the snow that fell overnight in the valleys and benches has already melted as temps have soared into the middle and upper 40s in some locations. In the mountain resorts, however, it has remained just below freezing, so only minimal melting has occurred with maximum solar radiation this afternoon. Looking at the broader view, a low pressure system is currently off the coast of northern California, and a large amount of moisture at middle levels is advancing ahead of it. The water vapor (moisture between ~600 hPa and 200 hPa) image shown below depicts an “atmospheric river” about to make landfall over California. This indicates that a large amount of precipitation could fall over the West and Intermountain West over the next 24+ hours.

Water vapor imagery from 15:30 MST this afternoon indicating a large amount of moisture entering into the West and Intermountain West. This is a precursor to large snowfall amounts that are expected in our area through early Friday morning. Courtesy:https://www.goes.noaa.gov/dml/west/nhem/weus/wv.html
Water vapor imagery from 15:30 MST this afternoon indicating a large amount of moisture entering into the West and Intermountain West. This is a precursor to large snowfall amounts that are expected in our area through early Friday morning. Courtesy: https://www.goes.noaa.gov/dml/west/nhem/weus/wv.html

Thursday and Friday:

Most lingering mountain snow showers should subside completely by early morning Thursday as peak short wave ridging occurs. However, as a shortwave trough approaches, expect waves of snow showers with  to pick up in the mountains starting around 6 AM MST. By early afternoon, snow showers should be widespread and steadily increasing in intensity. In the meantime, most models are picking up on a strong squall line of convection  within a baroclinic zone (separation of warm, less dense air with cold, dense air) developing over northwest Nevada and pushing through the valley into the Wasatch Mountains around 9 PM Thursday evening. During this time, extremely high snowfall rates of up to 3-4 inches an hour could occur for ski resorts over the northern Wasatch Front. After the baroclinic zone pushes through, cold northwesterly flow will induce orographic uplift and additional snowfall over the Wasatch through the night Thursday until early afternoon on Friday.

66312673
HRRR forecast radar reflectivity with precipitation type validThursday evening at 5 PM through Friday morning at  1AM. Green/yellow/red = rain/moderate rain/heavy rain, pink = mix of rain snow, and blue = snow. Darker shades of each color indicate heaver precipitation. This forecast radar loop indicates a strong line of convection moving through northern and central Utah. Within the convective line, valley rain should quickly turn to very heavy snow, and in the mountains extremely high snowfall rates will occur as it passes through. Courtesy: weathernerds.org

The image below shows the 72 hour snowfall accumulation forecast for northern Utah. Most mountain resorts look like they will receive AT LEAST a foot of snow, with the bull’s eye of accumulations occurring over the Cottonwood Canyon resorts; up to 3 feet of snow is possible for Alta/Snowbird and slightly less for Solitude/Brighton.

GFS 72 hr snowfall accumulations from Wednesday afternoon through Saturday afternoon. Most all of the precipitation will occur within the first 36 hours of the forecast period. Courtesy: weathernerds.org
GFS 72 hr snowfall accumulations from Wednesday afternoon through Saturday afternoon. Most all of the precipitation will occur within the first 36 hours of the forecast period. Courtesy: weathernerds.org

Saturday and Sunday:

Weak ridging will move into the area Friday evening through the weekend on Saturday and Sunday. However, a very weak piece of energy moving along the northern periphery of the ridge could slide into northern Utah and provide a little bit of mountain snow (0.5-1″) on Saturday, but don’t count on much of anything. Otherwise, expect mostly cloudy skies Saturday with a bit less cloud cover on Sunday. Overall, there will be GREAT ski conditions this weekend. Hopefully you can find some leftover powder too!

Long Term:

The next system with a chance for substantial snow looks like it will make its way into the area on Monday. A shortwave trough entering the northern California coast is forecast to move into and deepen over the Intermountain West. It looks to be a cold system with high snow ratios of at least 10:1 to 12:1 early Monday morning, and likely 15:1 to 20:1 snow ratios in the afternoon and early evening.

GFS forecast 500 hPa vorticity showing a strong, deepening trough pushing through the West and Intermountain West.
GFS forecast 500 hPa vorticity valid Sunday evening through early Tuesday morning. A strong, deepening trough looks to push through the West and Intermountain West. With high vorticity values (cyclonic spin and rising air), in addition to cold air in place and being advected by the system, we could receive another round of very good snow amounts. Courtesy: weathernerds.org

It’s tough to say at this point how much snow will fall Monday, but early indication is that it could be in the 12+” range for many resorts. We’ll keep an eye on it!

After that, there is indication from the global models that we will remain in a relatively cold, northerly flow regime with the potential for more snow-producing short wave troughs. Hopefully that pattern holds true! Stay tuned for more information on that and for any changes for the system affecting us Thursday and Friday.

-Pete

 

Wet Remainder of the Week

We are looking at a snowy remainder of the week across northern Utah, with a couple distinct rounds of snow. As Marcel mentioned yesterday, the first will be tonight into Wednesday, while the second round will impact us Thursday into Friday.


The First Wave (tonight-Wednesday):

A broad trough over the eastern Pacific off of the coast of California with moisture taps to areas with warm ocean water just north of Hawaii are what will bring snow to us for the rest of the week. While low elevation rain and high elevation snows have impacted California so far this week, the southwesterly flow have pushed moisture into the Great Basin throughout the day today.

Hourly mesoscale analysis from the Storm Prediction Center shows SW winds at 700mb transporting a large area of moisture into the Great Basin (green = Relative Humidity > 70%).
Hourly mesoscale analysis from the Storm Prediction Center shows S/SW winds at 700mb transporting a large area of moisture into the Great Basin (green = Relative Humidity >= 70%). Radar overlay also shows precipitation over much of California and a region of precipitation entering southern Utah at this time. (https://www.spc.noaa.gov/exper/mesoanalysis/)

Southern Utah has seen rain and snow already today, with Brian Head Resort reporting new snowfall of 4″ in the last 24 hours. Wintry conditions are visible from webcams at Brian Head and from road webcams on higher elevation roads in the southern half of the state.

Conditions at 3:30 pm local time from Brian Head Resort's Chair Seven Webcam at 11,000 ft. (https://www.brianhead.com/winter/chair-seven-cam/)
Conditions at 3:30 pm local time from Brian Head Resort’s Chair Seven Webcam at 11,000 ft. (https://www.brianhead.com/winter/chair-seven-cam/)

This moisture will continue to push northward into this evening, bringing snow to most of northern Utah beginning later this afternoon/evening and lasting into the mid-morning hours tomorrow for the mountains. The upper Cottonwoods have been in the clouds most of today, and an inch of snow has already been reported at Alta-Collins as of 4pm. Snow could end earlier across the valleys or transition to rain as the cold air pool is replaced with warmer air and the associated pollution mixes out. For the first round of precipitation, there is still a pretty large range of outcomes possible in terms of snow totals through tomorrow midday. Nevertheless, here are expected snow totals overnight tonight and into tomorrow:

  • Alta/Snowbird: 6 – 14″, but 8 – 10″ more likely
  • Brighton/Solitude : 4-12″, but 6-8″ more likely
  • Sundance: 3-7″
  • Snowbasin/Powder Mtn:  3-7″
  • Park City resorts: 2-6″

  • The Second Wave (Thursday-Friday):

While snow intensity should drop after tomorrow morning, the greatest chance for a lull in precipitation is Wednesday evening into Thursday morning. Don’t expect much clearing or sun, though, as orographic showers should continue – especially over the high terrain.

Winds will increase throughout the day on Thursday ahead of our next round of snow. This second round will be slightly different that the first since it will have a decent cold front and should have much higher snow totals than the first. Valley rain/mountain snow will begin Thursday morning under the next plume of moisture from the southwest. Current model guidance has a decent cold front with a wind shift from southwesterly to northwesterly in the overnight hours of Thursday night. This is when snow should really start to pile up!

It’s too far out to give much in terms of localized snowfall forecasts, but this second wave does look like it’ll deposit a good amount of water in our mountains to continue building up our snowpack and give us several powder days. Potential accumulations are large, but so is the range of possibilities. This morning’s 12Z downscaled NAEFS ensembles have the upper Cottonwoods in the range of 3-4 feet of snow (~3″ of liquid water equivalent) by Saturday with this week’s combined storms – just in time for the holiday weekend.


Tomorrow’s forecast should have a better handle on snow totals for the second wave as model runs iron out some of the details, so be sure to check back with us! Have fun and be safe with what should be a bombardment of fresh snow this week!

-Lucas

Waves of Snow at Resorts over Four Days this Week

If you’ve recently read our posts, you know that several storms are set to impact resorts this week. Here’s the breakdown for one of them, and I’ll allude to the other.


STORM ONE

Timing: Tuesday-Wednesday

Strength: Weak

Uncertainty: Moderate

I considered splitting this storm into two parts, but concluded that this will probably seem like one event anyway. This storm will consist of waves of precipitation, but waves generally increase in strength during the period.

Models are surprisingly uncertain about the strength of these waves and how they might be discretized, but they at least hint at two periods of heavier precipitation. Note the amorphous accumulations “thru Wed evening” in the figure below, which describe both waves in storm one:

snowstorm waves
NAEFS ensemble plumes at Alta-Collins station, initialized 5AM Monday Jan 14. Universal time (mountain standard time + 7 hours) on the horizontal axis increases to the right. Vertical axis is total estimated and accumulated snowfall since initialization. Note the scale of the vertical axis. Zoomed into the first event, you might be surprised at the variability in the ensemble totals. The variability in the totals during the second event are larger, but typical for such a large event size. Courtesy to weather.utah.edu

The first dump will be weak. Its precipitation rates maximize around noon Tuesday. The second dump is weak or moderate, and maximizes in strength mid-morning Wednesday.

Snow showers in this storm approach from the southwest. Winds should remain weak through the period but become more westerly (from the west) as the storm progresses.


Accumulations

I want to preface that the models are largely uncertain about this storm. For example, some ensembles suggest a range of 2” to 15” total snowfall in Little Cottonwood Canyon. A range of 13″ inches is large for a storm that might yield only 2″.

My perspective is that these storms are indeed as weak as we believe them to be, and will deliver on the smaller end of the range in the ensemble forecasts.

Finally, assume accumulations to vary quite a bit locally. Here are accumulations for resort locales during the Tuesday-Wednesday storm:

  • Wasatch Back (e.g. Park City): 2”-4”
  • North Wasatch (e.g. Snowbasin): 2”-5”
  • Sundance: 3”-6”
  • Big Cottonwood: 4”-8”
  • Little Cottonwood: 5”-10″

Other Comments

The storm should bring a blanket of fresh pow for those planning to hit the slopes Tuesday or Wednesday. FYI, looks like we’ll be under stormy skies until maybe Friday evening. Until then, the breaks in snowfall are most likely to be in the evening Tuesday and late Wednesday night.


Storm Two

Timing: Thursday-Friday

Strength: Moderate to Strong

Uncertainty: Small to Moderate

Next, models seem to agree that on Thursday afternoon or evening a strong snowstorm will impact much of the western US and dump quite a bit of snow in the Wasatch mountains. I think resorts can expect at least half a foot, some could see several feet of snow. Furthermore, the front will bring moderately cold temperatures and strong crest-level winds Thursday night into Friday. Something to watch closely—check back with us tomorrow for updates on this storm.

-marcel

This week should be better than last week

TLDR: Continued sun for most of Mon with increasing clouds on Tue and light precipitation late Tue into Wed afternoon (likely 3-6” during that span).  Then a more potent storm Thu morning through late Fri night.

Short-Mid Term:  Mountain sun and valley clouds/fog/smog will continue into tomorrow (Mon). Valley locations impacted by clouds today should see the same tomorrow.  Tue we’ll see increasing clouds throughout the day in the mountains with light snow beginning to fall Tue evening from a weak, but relatively moist, short-wave trough.  The bulk of precipitation with this trough will arrive Wed morning and early projections are 3-6” through Wed afternoon.

Long Term:  We’ll see a brief break late Wed with the leading edge of a stronger storm arriving Thu morning.  Snow will continue off/on through Thu night with the cold front arriving Fri morning and snow tapering off by Fri night.  If current forecasts hold, this should be a notable snow producer between Thu morning and early Sat morning…more to follow as we get closer.

Bright Sunny Day in the Mountains

It’s been a dark and chilly day along the Wasatch Front. It actually was snowing a bit in some places under the cloud. The air quality improved a bit today compared to the last few days. That’s mostly because there was a layer between the ground and the cloud where the air was mixing and the pollution could disperse.

Up in the mountains it was bright and lovely as could be. Of course it was very busy up there, but that’s to be expected in weather like this. Tomorrow is POW (Protect our Winters) Day, so be sure to carpool or take UTA to the mountains! The weather will be much the same tomorrow–clear blue skies with undercast to the west.

View from Snowbird's Hidden Peak this afternoon
View from Snowbird’s Hidden Peak this afternoon via National Weather Service

After Sunday, the weather will start to change again. Monday will be nice in the mountains, but high clouds will start to move in in the afternoon. Tuesday will bring a very weak storm to the area. It’s too early to say right now how much snow it will bring to the mountains, but it’ll at least be some refreshment. Also it might even be able to stir up the cold air pool and dissipate some of the pollution.

It will be a very stormy week next week compared to the past one. There’s the weak storm Tuesday afternoon I mentioned, and then there will be a strong storm between Thursday and Friday. If the pollution doesn’t go away Tuesday it’ll surely go away Thursday. Right now it looks like the mountains are going to do very well from the Thursday/Friday storm. And, if we’re lucky, the clouds will clear out before the lunar eclipse Sunday night. Be sure to keep an eye on the forecasts over the next week!

Up above, down below

It’s one of those days where it’s just impossible to convince yourself to drive home at the end of the day, knowing that you’re about to trade a view like this:

Salt Lake Valley from Hidden Peak, courtesy of Snowbird
Salt Lake Valley from Hidden Peak, courtesy of Snowbird

For one a little more like this:

U of U William Browning Building West View
U of U William Browning Building West View

While we have been under a strong surface inversion for the majority of the past few days here in the Salt Lake valley, since yesterday evening, the inversion has deepened. as well as become quite moist. The dense fog and low-level cloud make that quite evident. Though the air quality is becoming steadily worse as pollutants accumulate, the deepening of the inversion has likely slowed the process some. For those interested in the air quality, the ‘official’ measurements show us sitting solidly in Unhealthy for Sensitive (~36 µg/m3) for the majority of the past 24 hours.

Utah Department of Environmental Quality Air Quality PM 2.5 Concentration for Salt Lake (Hawthorne)
Utah Department of Environmental Quality Air Quality PM 2.5 Concentration for Salt Lake (Hawthorne)

So when will it end? When’s the next snow? Well, models hint at a very weak inverted trough to impact our regional weather by the end of the weekend into Monday. The low-level easterly flow models hint will be associated with this passage may help weaken the valley inversions by the advection of colder air aloft – weakening the vertical temperature gradient and allowing for a little mixing. Additionally, drier air from the east may help clear some of the fog and low cloud, though where exactly is not clear – the northern end of the Wasatch seems favored.

Tuesday afternoon GFS forecast 500 mb Heights and Vorticity. Note that the stubborn ridging over the Intermountain West has given way to more zonal flow ahead of the broad trough to our west.
Tuesday afternoon GFS forecast 500 mb Heights and Vorticity. Note that the stubborn ridging over the Intermountain West has given way to more zonal flow ahead of the broad trough to our west.

By Tuesday we finally see more zonal flow, and the weakening of the ridge may finally release the valleys from the inversion’s grasp. Instability and weak synoptic forcing for lift and precipitation will be present across the region, but it’s hard to say how much snow to expect at this point – anything from flurries to feet is possible by the end of next week. Stay tuned and we’ll let you know as we know.

Significant uncertainty exists in the ensemble forecasts due to the broad, weak nature of the trough. We'll wait before diving in to this one.
Significant uncertainty exists in the ensemble forecasts due to the broad, weak nature of the trough. We’ll wait before diving in to this one.

-Mike

 

Dusting of Snow Then Sunny

TLDR: Weak snow showers passed through the area and may linger to produce a trace of snow overnight.  Expect sunny skies in the mountains for the weekend with some weak disturbances by the middle of next week.

If you saw gray skies, falling flakes, or rain drops this afternoon and hope snow is accumulating in the mountains then please take a look at the Park City snow stake image below.

https://www.wrh.noaa.gov/images/slc/camera/loopCams.php?camName=canyonssnowstake&numFrames=10
https://www.wrh.noaa.gov/images/slc/camera/loopCams.php?camName=canyonssnowstake&numFrames=10

A weak cold front and light precipitation moved through northern UT this afternoon but the frontal precipitation has ended with only a trace across the mountains.  A few trailing showers will give a dusting to the mountains this evening, but another trace is likey and 1” would be generous.

The Weekend:  Sunny skies with a warming trend will dominate the weekend, with temperatures above freezing across most of Utah’s ski resort terrain Sat and Sun afternoon.  Inverted temperatures from the valley to mountains (i.e. temperature warming with height instead of cooling) mean valley pollution will have nowhere to go over the weekend, so the mountains will be the place to be.

Long Term:  Some clouds from a system to our west are slated late Mon-Tue with a small storm currently forecast for Wed-Thu.  However, we’re far enough out that details are inconsistent for Wed-Thu.

-Tyler

Weak System then Bluebird Weekend

After an active few days, we can expect generally quiet conditions for the next few days. Today was mostly cloudy as southerly winds picked up out ahead of weak system. Tomorrow a weak front will cross through northern Utah midday. I’m not expecting much more than a few snow showers that may drop an inch or two in the central and northern mountains. The 26-member SREF shows most members producing less than 0.2″ liquid or about 3″ of snow at Alta.

SREFPL_CLN2019010921F087

High pressure takes over from Friday through Sunday, featuring sunny skies, calm winds, and mild temperatures in the mountains. Air quality will likely go down-hill in the valley as an inversion sets up and traps emissions. I’ll be spending my weekend up in the mountains like I’m sure many others will.

Models are starting to indicate that active weather will return to the region around next Tuesday. Below is the mean sea level pressure anomaly from the Global Ensemble Forecasts System (GEFS). Its advertising that the trough currently off the coast of California will begin to move east and bring unsettled weather back to Utah.

gefs_slp_stdev_noram_31

Enjoy the upcoming beautiful weekend out on the slopes!

Quiet weather continues

We’ve had good fortune the past several days with high-producing troughs that have given us quite a bit of mountain (and valley) snow. Yesterday and today, though, have been quiet with gorgeous skiing/boarding conditions. Some high clouds have started moving into the area this afternoon, but there has been plenty of sun throughout the day. Below is a view from Powderhorn Lift at Solitude from this afternoon.

View from Powderhorn lift at Solitude Mountain Resort at 14:24 MST. Courtesy: https://webcams.solitudemountain.com
View from Powderhorn Lift at Solitude Mountain Resort at 14:24 MST showing some high clouds with ample sunshine still. Courtesy: https://webcams.solitudemountain.com

What’s Next?

A weak trough out of the Pacific will make its way into our region Thursday morning/afternoon. It looks, however, like it will be relatively moisture starved, and with weak dynamics associated with this trough we should only expect 0.5-1″ of snow with this system. Below is the GFS forecast for 500 hPa vorticity and 700 hPa relative humidity (green contours) showing the approaching trough with limited moisture approaching our region Thursday.

GFS 500 hPa geopotential heights (black contours), 500 hPa vorticity (shaded) and 700 hPa relative humidity (green contours) showing approaching weakening trough with attendant limited moisture. Courtesy: weathernerds.org
18z GFS forecast 500 hPa vorticity (shaded) and 700 hPa relative humidity (green contours) showing approaching weakening trough  with attendant limited moisture on Thursday. Courtesy: weathernerds.org

Behind that, another trough will enter the continental U.S. on Saturday but looks like it will stay to our south over southern Arizona and New Mexico, leaving us high and dry. The good news is that temperatures will be relatively pleasant in the mountains this week with highs in the upper 20s – low 30s.

By the middle of next week, models are picking up on a couple of troughs that could produce some appreciable snow amounts beginning Tuesday evening. Stay tuned for more information on the potential storms next week (and for any possible changes on forecast snow totals Thursday), and enjoy the comfortable ski conditions!

-Pete