Wrapping Things Up

While skiing in the Wasatch will continue for weeks to come, this is our last scheduled forecast of the 2017-2018 season. Most resorts have had closing day festivities and shut down their bullwheels over the last several weekends or have switched to a limited schedule. The following lists resorts that still have plans to remain open:

Resort Scheduled Closing
Alta Sunday, May 6 (weekends only)
Brighton Sunday, April 22
Snowbird TBD (First Weekend in May?)

Alta wrapped up their weekday openings yesterday, but still hopes to provide some skiing the next few weekends. Brighton has 6 days left for their 2017-18 season. Snowbird doesn’t have a defined closing date, but I’d guess they’ll try to stay open at least though the first weekend in May (#LongestSeasonInUtah).

However, we still have snow on the way starting this evening! A cold front is racing across the Great Basin this afternoon and will bring some precipitation as it passes through Northern Utah. It’s also pretty windy, warm, and dusty out there! Temperatures are near freezing at ~11k feet and Mt. Baldy has been reporting southerly gusts to near 70 mph. Here’s a view from Hidden Peak looking down into the Salt Lake Valley.

12:15 pm view toward the WNW from Hidden Peak at Snowbird. (http://prismcam.com/demos/snowbird-peaks/)
12:15 pm view toward the WNW from Hidden Peak at Snowbird. (http://prismcam.com/demos/snowbird-peaks/)

As far as snow totals for overnight and into Tuesday, it won’t be a major storm, but some favorable postfrontal cold air and moist NW flow Tuesday morning may bump up the amounts (possibility for some lake effect exists). I’m going to go with around 3-6″ this evening and overnight, and maybe up to an additional 3-6″ if we really get some postfrontal goodies on Tuesday. Tomorrow should be a fun day with a little dust on crust!

It’s looking to get much warmer after this storm and as we progress through the second half of April, with possibility of a hint of precipitation later this week.

GEFS Ensemble for SLC through the end of April expecting warmth - 16APR00Z model run. (http://www.wetterzentrale.de/en/show_diagrams.php?geoid=135917&model=gfs&var=205&run=00&lid=ENS&bw=)
16APR00Z model run of GEFS Ensemble for SLC through the end of April expecting warmth to dominate (http://www.wetterzentrale.de/en/show_diagrams.php?geoid=135917&model=gfs&var=205&run=00&lid=ENS&bw=)

Thanks for your readership of Utah Ski Weather – we really appreciate it! We’ll be back in the fall to give forecasts for the 2018-2019 season!

-Lucas

More Snow This Week: Featuring Some Lake Effect

snow level
Snow levels in Logan, UT. (photo courtesy utahavalanchecenter.org)

Hey skiers,

Last Thursday/Friday’s storm made for some great runs, and wild clips like this one from @Snowbird resort Friday:

These marked the last runs of the season for many Utah resorts, but not quite the last hoorah from mother nature.

Still able to squeeze in some skiing sometime this work week? Watch for a powder dump in the canyons early on. Here are the details:


THE FORECAST

Another cold front will cross northern UT and deliver some snow to Wasatch resorts. I expect there to be a lake-effect component to total snowfall and snowfall variability within the impacted area.


Timing

Precipitation beginning with frontal passage sometime Monday evening/night, lasting through the AM Tuesday.  Moderate uncertainty.


Location

Highest amounts in the Cottonwood canyons (small uncertainty), however snowfall across the Wasatch range (small uncertainty). Small accumulations in the valleys are possible (moderate uncertainty).


Accumulations

A couple of inches across the Wasatch range, 3-5 inches in little Cottonwoods, and locally higher amounts are possible (high uncertainty).


Comments on Lake Effect:

The Salt Lake will have had two days of warm temperatures and April sun by Monday night. Given that, plus a moderately cold air mass behind the front, could bring us enough instability for a brief lake effect period after the front passes. Next, the fetch (over-the-lake distance) of the wind flow will be largest sometime early Monday morning, at which point I’d expect a maximum in the strength of the lake effect.

Last week, we saw a lake effect period that brought several inches of extra snow to Utah County the west benches of Salt Lake County. However, there is some uncertainty in the length of Tuesday morning’s lake effect period, and therefore uncertainty in snowfall amounts for the areas impacted.


Enjoy the snow this week!

-Marcel

Winter Returns

After a relatively warm period over the past several days, a strong cold front will move through the state early tomorrow morning. A frontal band of heavy precipitation will bring snow levels crashing down to the benches and likely even valley floors (though accumulations on pavement should be limited). After the initial burst of precipitation, a brief lull will be followed by cold, moist northwesterly flow. For accumulations I’m expecting 7-14 inches for most areas mid-mountain and higher. The post-frontal wild card could also certainly bump totals higher in the Cottonwoods.

ecmwf_tprecip_slc_11
ECMWF liquid water forecasted through Friday evening

Conditions will rapidly warm up over the weekend making way for some very nice spring skiing. Another storm may impact Northern Utah Monday-Tuesday.

 

Wet and Warm Storm

The next round of wet weather in the Wasatch Mountains starts tomorrow. An incredibly wet system is moving off the Pacific and dragging a lot of tropical moisture into the western United States. Scattered showers are possible at any time this weekend, but most of the precipitation here in Utah will fall in two waves. The first wave will be Friday morning and the second will be Saturday afternoon into the evening.

The incoming storm, via NOAA
The incoming storm, via NOAA

The snow levels should be above valley floor for this entire event, but which elevations in the mountains are getting snow will vary over the weekend. For the first wave tomorrow morning, snow levels will be relatively low. Elevations above 8000 feet should be seeing the white stuff and 3-5″  of wet snow will fall during this time. Once the precipitation becomes more showery later Friday, temperatures (and snow levels) will start to rise. By Saturday morning melting will pass 10000′ and further showers will mostly manifest as rain.

Most of the storms this winter have had large model spreads, and this one is no different. The uncertainty with this one is due to differences in moisture availability and the wind. Most of the day Saturday will be spent in a super-moist pre-frontal environment, and if the setup is just right the mountains will get a lot of precipitation. Unfortunately snow levels at this point will be over 12k feet and it would be a lot of rain. The range model right now is between 0.5″ and 2″, but an inch of rain looks to be most likely.

Around 5 in the evening a strong cold front comes through and switches the rain to snow overnight. By Sunday morning any pop-up showers that do form will be snow in the mountains, but it will be very hit-and-miss. All in all this weekend will be a whole lot of rain and not that much snow. It’s April, so we can’t expect too much. Hopefully we can get a colder storm later in the month.

Interesting week ahead…

A quick hitting storm is lined up for the end of the week, with most of the precip occurring Thurs afternoon through Friday morning. This one will be the colder of two upcoming hits, with snow levels starting high, around 9200′ then falling towards 8000′. At only .3-.4″ of water for the upper Cottonwoods, this will put down 2-4″ of dense cream-cheese-like snow, with the possibility of light rain at some resort bases to start as temps fall. Upper elevations should remain all snow, but again, I’m expecting closer to 10:1 for this event.

NAM 12km meteogram for Alta Collins
NAM 12km meteogram for Alta Collins

The second event of note is this weekend’s storm, and as Trey mentioned it will be more of an atmospheric river type event, with ample moisture but warm southwesterly flow. The GFS meteogram hints at the problem: note the accumulating water but not snowfall, with temps at 700 mb just flirting with the 0 C mark. It is almost certain that resort bases (and possibly up to 11 k ft!) will see a prolonged period of rain to start the event. As the trough comes through and ushers in colder air, models suggest that the last 0.5″ or so of precip may fall as all snow. At a forecast 3″ of water, this has the potential to cause some major change to the snowpack. While the skiing inbounds could be okay on top of the new snow (elevation and timing dependent as event nears) the backcountry snowpack will likely be in a dangerous state.

GFS meteogram for Alta Collins
GFS meteogram for Alta Collins
An impressively wet GFS time-height plot showing the Friday quick hitter and the prolonged saturated column with the weekend's AR event
An impressively wet GFS time-height plot showing the Friday quick hitter and the prolonged saturated column with the weekend’s AR event

Fickle Spring Skiing

Today’s storm has brought 2-4 inches to most mountain locations as expected. While all new snow is always welcome, this will unfortunately not be enough to cover the crust that’s now on all aspects except high north. The other big story was the breezy conditions and colder temperatures today. Because of the much higher sun angle this time of year, though, things will quickly warm back up by Wednesday before additional chances for some snow showers late week.

Overall, this week isn’t looking too great in terms of conditions. For good April spring skiing I typically want a big dump of snow or clear skies/relatively warm days for a good corn cycle. It looks like this week will be neither. We’ll likely see enough snow and clouds to prevent a good corn cycle but also not enough snow to cover up the sun crust. Nevertheless, ski season will quickly begin to wind down over the next month, so we gotta enjoy what we get!

Precipitation forecast from the ECMWF for SLC this upcoming week
Precipitation forecast from the ECMWF for SLC this upcoming week

Looking ahead towards the weekend, there is a potential Atmospheric River (AR) event on the horizon. Remember AR events are typically characterized by significant precipitation but also “high” snow levels. It’s too far out to get into details, but just something to keep an eye on over the next few days.

Refresher

This weekend was spring skiing at its best. Hope you enjoyed the beautiful weather! Nothing big on the horizon storm-wise, but we’ll get a nice little refresher tomorrow (Monday).

An upper-level shortwave trough will move through quickly on Monday with a cold front at the surface arriving sometime around mid-day. Temps will drop quickly, with a band of precipitation moving through, and  snow levels falling to the valley floor by evening. The precip looks to end quickly after the front moves through though, so snowfall amounts will be pretty meager. I’d expect 3-6″ in the upper Cottonwoods, with 1-4″ elsewhere.

Screen Shot 2018-04-01 at 9.43.07 PM
Precipitation accumulation through Tuesday from the ECMWF model
Screen Shot 2018-04-01 at 9.46.00 PM
Precipitation accumulation through Tuesday from the GFS model

We warm up and dry out through the week, with a storm looking increasingly likely on Friday, and maybe into the weekend.

Out Like a Lamb

If you recall one of our forecasts from earlier in the month of March, I wrote about March was appearing to come “In Like a Lion”. In that post, I longed for a boost to our snowpack and the continuation of storms through the month. However, we are definitely going to end March like a lamb.

Fortunately, March was both helpful and devastating to our snowpack. The first several days of March were plentiful with snow –  with about 30″ falling in the upper Cottonwoods and about half that amount elsewhere. Another cold storm system for St. Patrick’s Day weekend was beneficial too, depositing another 1.5-3′ of snow into our Wasatch Mountains. But just a few days later, an extremely warm period brought rain to even high elevations in the Cottonwoods. This resulted in our scarce low-elevation snowpack to melt and lose some of its snow water, while upper elevation snowpacks were able to soak up that rain and hold it in the snowpack to increase our SWE.

One example of a low elevation site that experienced rain and melt is Ben Lomond Trail (elevation: 5972 ft), as shown by the following SNOTEL water year graph. The rainy events are easy to notice when precipitation accumulation (black line) increases, but SWE (blue line) decreases for a storm period- look especially at the latter half of March.

Ben Lomond Trail SNOTEL water year chart as of March 29, 2018.
Ben Lomond Trail SNOTEL water year chart as of March 29, 2018.

So overall, high elevations did decently well during March (Alta has reported 93.5 inches of snow on the month comprising 8.79 inches of liquid water). In comparison, the average March snowfall at Alta is ~100 inches, or 7.82 inches of water. Unfortunately, we still are’t sitting super pretty on the season and there is not much to look forward to in the next few days. (Data from https://www.alta.com/conditions/weather-observations/snowfall-history).

Looking back to the sad time of two months ago and comparing it to now, we can notice some improvement based on SNOTEL stations. (https://www.wcc.nrcs.usda.gov/webmap/).

January 29, 2018 SNOTEL snow water equivalent as percentage of median
January 29, 2018 SNOTEL snow water equivalent as percentage of median
March 29, 2018 SNOTEL snow water equivalent as percent of median
March 29, 2018 SNOTEL snow water equivalent as percentage of median

In these images, white circles represent near normal, greens and blues represent above normal and well above normal, and oranges and reds represent below normal and well below normal. Some areas have made quite the comeback in the last couple months, but overall this year’s above normal snowpack in the northern Rockies has persisted.

As for the next few days and into the Easter weekend, not much exciting weather is in store besides warm and dry conditions. We are expected to run 5-10+ degrees F above average for this time of year, and no major storm systems are aimed at our area in the coming days. Perhaps a skiff of snow is possible into Sunday, but don’t expect anything much more than that.

Have your sunscreen and warm weather gear ready for this holiday weekend and enjoy the spring conditions!

-Lucas

A Look at the Week Ahead

TLDR

Warm and mainly dry weather is expected through the end of the work week.  Light snowfall accumulations of a few inches are possible Wednesday across resorts in northern Utah.

Short-Term Forecast

Clear skies and warmer temperatures are expected Tuesday afternoon under mostly sunny skies.  A weak storm system will brush across northern Utah Wednesday bringing light accumulations, with snowfall totals of around a few inches.

GFSET_KSLC2018032618F120
GFS time height cross-section of wind speed and relative humidity. Courtesy of weather.utah.edu

Looking ahead at the rest of the work week, upper level ridging is expected off the west coast.  This will lead to a period of calm winds, mostly sunny skies, and warm temperatures.  A weak disturbance could enter northern Utah over the holiday weekend, but any accumulations will be on the light side of the spectrum.

ecmwf-ens_z500a_namer_3
ECMWF Ensemble of 500 mb geopotential height anomaly for Wednesday morning. Courtesy of tropicaltidbits.com

-Alex

Something to cover up the rain crust

It rained a lot yesterday and last night, and it did it up to 9,500ft in most areas. Rainfall totals in the Cottonwoods and the southern Wasatch were generally the 2-3″ range, with closer to 1″ in the northern Wasatch. Things cooled off a bit last night and snow levels dropped to around 7,000ft this morning, with most areas picking up a few inches of dense snow before the precip shut down by late morning. Areas above 9,500ft got slammed with large amounts of very high density snow, but everywhere else, this storm was a disaster.

Screen Shot 2018-03-23 at 5.06.07 PM
The Park City webcam sums up the conditions this morning pretty well

Fortunately, the forecast for this weekend and early next week does have some snow for the Wasatch, and maybe even down to the valley floors. The amounts are not super promising, but they’ll hopefully be enough to cover up the rain crust a little bit. It looks like a quick couple inches Saturday night, followed by a slightly stronger shortwave trough moving through on Sunday. For Sunday’s totals, I’ll go with 4-8″ at the moment. Sunday’s storm looks to be a cold one, with favorable cold northwesterly flow behind it into Monday, so that snowfall forecast may go up.

Screen Shot 2018-03-23 at 5.16.05 PM
Time-height diagram from today’s 12z run of the GFS model

After that, we slowly dry out and warm up into the work week.