Another Strong Storm Arrives Sunday

Today turned out to be a deep day in the Cottonwoods with 1-2 feet plus falling in a few locations.  Snow water equivalents are 150-200 percent of normal as we continue to reap the benefits of an active storm cycle!

Storm totals over the last 48 hours

  • Brian Head 27″
  • Alta Collins 26″
  • Brighton Crest 23″
  • Snowbird 20″
  • Deer Valley 15″
  • Solitude 15″

Another strong storm system will impact Utah Sunday through Tuesday afternoon.  A strong upper level low is currently spinning off the coast of Oregon and Washington with a plume of subtropical moisture streaming into central California.  Ridge top winds are expected to increase from the SW overnight as the trough slowly progresses eastward.  By tomorrow afternoon winds could approach 80-100 mph.  Lift associated with a shortwave trough, diffluent upper level jet, and warm air advection will allow for widespread snowfall across the Wasatch Sunday afternoon into Monday morning.  During this period, strong SW winds will favor SW facing aspects, with the northern Wasatch (Snowbasin and Pow Mow) seeing significant snowfall.  Park City and Big Cottonwood Canyon resorts will be also favored during this time.

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GOES IR Satellite across the Western U.S.

Heading into Monday, a cold front will sweep across the Wasatch Front during the late morning into the afternoon with winds switching to the W-NW. Along the cold front, heavy snowfall is expected with resorts in the Upper Cottonwoods being favored.  Another period of snowfall is expected Monday evening through Tuesday morning as wrap-around snow forms along the NW sector of an upper level low centered in SW Wyoming.  By Tuesday morning 700 mb temperatures will cool to around -15 C allowing for low density Utah powder with ratios near 20:1.

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Simulated radar reflectivity from the GFS through Wednesday morning.

Summary

  • Strong ridge top winds nearing 80-100 mph Sunday afternoon into Monday morning.
  • Northern Wasatch, Park City, and Big Cottonwood resorts favored until cold front arrives Monday late morning.
  • Upper Cottonwood resorts favored Monday afternoon through Tuesday morning.

Snowfall Forecast through Tuesday Afternoon

  • Park City Resorts: 14-24″
  • Big Cottonwood Resorts: 18-30″
  • Little Cottonwood Resorts: 20-36″
  • Northern Wasatch Front Resorts: 14-24″

2 Troughs, 1 Ridge

While this week wasn’t a huge one for snow totals, the resorts still enjoyed a semi-powder day today. The good news is, more is on the way.

Trough 1:

After a quiet day with much better air quality (finally), we can expect the action to start again in the overnight hours.  A shortwave trough will move in to the Great Basin in the overnight hours bringing with it some light.  Snow levels will be at the valley floor for the duration of the event with temperatures not recovering to above freezing until noon Sunday. The highest precipitation rates should occur in the early morning hours with the moisture streaming in from the southwest.

HRRR simulated reflectivity.
HRRR simulated reflectivity.

Unfortunately, the surface low associated with this trough will pass to our south, robbing the Wasatch of the highest snowfall totals.  Through Saturday, the Wasatch will likely see 8-12″ with over a foot expected for our friends down south.

Trough 2:

The break in the action will be a short one as trough number two progresses into the area on Sunday.  Snow levels will initially stay elevated with the warm air advection and gusty southerly winds prior to the frontal passage.  After the passage, temperatures will drop and winds will shift to WNW which will get the orographic enhancement cranking. With this second trough we are looking at 1-1.5″ of QPF and the possibility for an additional 12-18″ of powder through Monday.  Totals could be on the higher end, depending on how much moisture we can condense out with that favorable northwest flow.

GFS Forecasted Meteogram for Alta, UT
GFS Forecasted Meteogram for Alta, UT

Ridge:

BOOOOOO. GO HOME RIDGE.  And boy, its an ugly one.  Unfortunately, this guy is gonna stick around through the end of the month.  Get your powder days while you can!

GFS Mean Sea Level Pressure valid 27 January
GFS Mean Sea Level Pressure valid 27 January

Small But Nice Storms

Thursday’s storm system has come and gone and treated us to a nice refresher. Snow totals from the storm weren’t that high despite it snowing all day long, and Alta reported 5″ from it. Unfortunately for those of us in the valley, it wasn’t enough to destroy the pollution layer. We enjoyed clean air during the event, but just before sunset the winds shifted and a toxic freezing fog rolled in from the lake. Here’s a video from the University of Utah’s Atmospheric Science department showing the fog rush in.

The weather in the mountains Friday is going to be very nice. Party cloudy skies, weak winds, and nice temperatures are on tap. Given that the air quality in the valley is already unhealthy, I recommend minimizing your impact during your escape by carpooling and taking the bus.

Our next storm comes Saturday and it looks remarkably similar to today’s. It’ll come slightly earlier in the day, but another 3-6″ is in store for the mountains. After the storm winds will pick up to around 30 mph high in the Cottonwoods. Sunday is another intertempestas (not a word currently but I’m going to make it one) but unlike Friday it will be cloudy and windy.

Monday is a storm with more potential. A very cold air mass will be approaching from the north, and there is a potential for a Great Basin cyclone to develop. The GFS model shows a depression forming on the lee-side of the Sierras and deepening as it approaches northern Utah. The dynamics of this storm will determine who’s a winner and who’s a loser. The GFS is currently modeling a northerly track that sets up a band just south of the Cottonwoods.

gfs_6hr_precip_cw_17

It’s easy to see how the slightest change in track could drastically change the forecast, and, as such, I won’t attempt to put totals on Monday’s storm. There is large uncertainty with the ECMWF model bringing the low center over the southern Wasatch. In any case, Monday’s storm is promising to be larger than either Thursday’s or Saturday’s.

One, two, three… Go!

After a string of great sunny days up in the mountains, I think many of us are pretty ready to see some new snow! As Tom mentioned, the next week will see the passage of three somewhat distinct systems. Checking out the recent to current observations, we can see clouds moving in to Utah from the west as we progress into the afternoon, with radar illustrating showers beginning to spread through Nevada. California, once again, is seeing a significant slug of moisture with this system, though with snow levels a bit lower than the last event.

Visible Satellite + Composite Radar Loop w/ surface Observations Through 2PM MST 18 Jan
Visible Satellite + Composite Radar Loop w/ Surface Observations through 2PM MST 18 Jan

With the low moving through to the south, the first system will not have clearly defined fronts for the central and northern Wasatch, and will see precipitation light, steady, and spread out from Thursday morning around sunrise through early afternoon Friday. Totals for this period will be modest, with 3-6” expected for the northern Wasatch, the Cottonwoods, and Park City area, and slightly higher totals around 5-10” towards the southern edge of the range/central Utah.

The second system begins Friday night after a brief break in precipitation (though light snow showers may continue uninterrupted across high terrain, driven by the topography). This system is likely to bring precipitation, once again in a weak and poorly organized manner for Northern Utah, through Saturday evening. We’ll likely see an additional 4-8” of snow in the upper Cottonwoods and Park City, with possibility of 6-10” at upper elevations, 4-7” for the Northern Wasatch, and 3-6” for the southern end of the range/central Utah. Without strong dynamical support, we could see this system fizzle a bit – we’ll update tomorrow and see how the models handle it as it gets closer.

GFS Time-Height Plots, indicating the three distinct systems to move through the region. The third is the most significant, but also carries the most uncertainty, being the furthest out. Note the limited convective instability due to the disorganized nature of the system and position of the low to our south.
GFS Time-Height Plot of RH and Equivalent Potential Temperature, indicating the three distinct systems to move through the region. The third is the most significant, but also carries the most uncertainty, being the furthest out. Note the limited convective instability due to the disorganized nature of the first two systems with their position of the low to our south.

The GFS produces a significant system in the region for Monday. Spread in the ensembles is still very large, and so I’ll hold off on talking about the system in detail. The bottom line is, we can expect a decent refresh after the weekend for the midweek skier’s enjoyment.

ECMWF 7-Day 500mb Height Anomalies for period beginning (clockwise) 30 Jan, 03 Feb, 06 Feb, 10 Feb.
ECMWF 7-Day 500 mb Height Anomalies for periods beginning (clockwise from top left) 30 Jan, 03 Feb, 06 Feb, 10 Feb.

I’ll briefly address the elephant in the room, as other resources in the area have already brought it to light. Following this week’s storm cycle, models suggest significant and prolonged ridging and high pressure over the intermountain west through the middle of February. These plots can provide guidance as to the intensity and duration of high pressure for us at the surface, but do not provide exact details. A 7-day average anomaly is just that – averaged over 7 days. It’s not out of the question for weak troughs (low pressure systems/storms) to roll through during a period otherwise dominated by ridging. This signature weakens beyond the first week of February, both an indicator of the ridge breaking down and the uncertainty inherent in medium-to-long range forecasting.

Active Weather Returns

One more day of mild, bluebird conditions up in the mountains and smog in the valley before the next storm system pushes into the region. Between Thursday and Monday 3 systems will cross through the region as shown in the animation below from the GFS.

Animation from GFS
Animation from GFS

Storm #1 will skirt through southern Utah Thursday morning through Thursday night.  It looks like northern Utah will miss the brunt of this storm. Totals should range from 6-12″ in northern and central Utah to 12-20″ in southern Utah down by Brian Head and Eagle Point.

Storm #2 will enter the region Saturday morning and it too appears to track through southern Utah and northern AZ/NM.

Storm #3 has the potential to be much stronger than the two before it.  It’ll impact Utah on Monday.  Keep an eye on this one – the NAEFS shows the potential for a significant system.

1/17/16 12Z NAEFS forecast for Upper Cottonwoods
1/17/16 12Z NAEFS forecast for Upper Cottonwoods

Previewing the Week Ahead

Valley cold air pools (“inversion”) will continue through Thursday morning before a cold front clears things out Thursday night into Friday morning.  Across the valleys, air pollution has only managed to reach the moderate category so far, with the exception of Cache Valley, where air quality has reached the unhealthy for sensitivity groups category.  A deep cold air pool is currently in place with the top of the inversion around 7500 feet.  Typically during inversion events, the top of the inversion is between 5500 – 6000 feet.  With the top near 7500 feet in this event, pollution is able to spread out through a deeper layer of air, keeping PM2.5 concentrations on the lower side.

Salt Lake County PM2.5 trend from Jan. 12 to Jan 16th. Courtesy: http://air.utah.gov/trendcharts.php?id=slc

High pressure will remain in place across Utah through Thursday morning.  700 mb temperatures will warm from around -5 C tonight to -1 C by Tuesday afternoon, yielding warmer temperatures (30-35 F) across ski resorts Tuesday and Wednesday.

A series of storms will move through Utah Thursday afternoon through Monday.  The first storm will arrive Thursday afternoon, with best dynamics across central and southern Utah.  Snow showers will develop Thursday afternoon before tapering off Friday morning.  Another shortwave trough will arrive Friday afternoon.  Once again this storm will mainly impact central and southern Utah will light accumulations across northern Utah.  A stronger storm will impact northern Utah Monday, but this system is a week out, with details easily changing by then.

NAEFSPL_CLN2017011612F168 (1)

NAEFS Precipitation and Snowfall Forecast for Alta. Courtesy: weather.utah.edu

Bottom Line

  • Tuesday will be another blue bird day with slightly warmer temperatures.
  • Wednesday will be another great day with high clouds moving in by the afternoon.
  • Active weather returns to Utah Thursday through the weekend with a series of storms dropping new snowfall.  The first two storms will be on the weaker side, but could drop anywhere from 6-16″ across the Wasatch.

Hazy days

A quiet weather weekend gave way to gorgeous conditions at the resorts.  You were treated to blue bird mountain conditions if you climbed up high enough to escape the inversion currently blanketing the city.
Our current break from the storm cycle is disrupting the air quality in the valley, causing PM2.5 particulates to build up.  This results in that foggy haze that you woke up to this morning. Unfortunately, this inversion episode will likely stick around until Wednesday.

The active pattern appears to return Thursday with a shortwave trough making its way into northern Utah.. While this storm appears to be colder than the previous few, it still looks like we will see only rain in the valley due to elevated snow levels. This active pattern should continue through the weekend.

ECMWF 500 mb heights. Valid 18 Z Thursday. Image: Weatherbell
ECMWF 500 mb heights. Valid 18 Z Thursday. Image: Weatherbell

Thanks to the active pattern we have been blessed with since the beginning of the year, snowpack SWE levels are well above normal.  Lets hope this coming week can add to it!

Current SNOTEL Snow Water Equivalent percentage of normal.
Current SNOTEL Snow Water Equivalent percentage of normal.

Enjoy the Sunshine

Not a whole lot to talk about tonight, so I’ll keep it brief. A tremendous storm cycle has left the skiing across the state of Utah in spectacular shape. The backcountry will finally have a chance to (slowly) stabilize this weekend as winds remain light and no new snowfall is expected. For those of you about to enjoy a three day weekend, it should be a beautiful one, with ample sunshine Saturday, Sunday, and Monday at the resorts.

Down in the Salt Lake Valley we’re watching the development of an inversion leading to decreased air quality this weekend, with the effects already noticeable today. Carpool to the resorts if you can, and help limit our contribution to the pollution during this period.

Vertical profile for SLC from the NAM12. Note the development of a significant inversion, where temperatures (rightmost red line) warm with height in the lower levels.
Vertical profile for SLC from the NAM12. Note the development of a significant inversion, where temperatures (rightmost red line) warm with height in the lower levels.

 

500 mb heights fall significantly by late next week, indicating the return to troughing to our west and another stormy period into next weekend. Way too soon to talk much about details but it looks to be a colder storm than the last few that impacted the state. Stay tuned, and enjoy the skiing!

ECMWF ('Euro') Ensemble Meteogram. Ensemble members show strong agreement in a period of significant precipitation beginning midweek, Jan 18-22, then uncertainty out beyond some light precipitation to end the week.
ECMWF (‘Euro’) Ensemble Meteogram. Ensemble members show strong agreement for a period of significant precipitation midweek, Jan 18-22, then large uncertainty beyond a period of light precipitation to end the week.

Finally, a Break

This current storm cycle has finally come to an end.  We didn’t do too bad in Utah, as Alex pointed out, but the true winner was the Sierra Nevada.  Mammoth Mountain is reporting a storm total of 101-154″ with a summit base depth of 245″!!! (I’m skeptical about that measurement)  The snowpack across most of the west is looking very healthy as we head into the heart of the winter.  Most SNOTEL sites are reporting 125-200%+ of their median SWE for today.

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SWE percent of Median for SNOTEL sites from NRCS

The next several days look sunny and dry for the entire region.  Temperatures will be comfortable with highs in the upper 20’s in the mountains each day.

All models agree that active weather returns on Wednesday next week.  It’s early, but it looks like we could be in for another prolonged stormy stretch.  Stay tuned!

Snow Continues in the Wasatch through Friday

Snow just keeps on flying in the Wasatch! Snow totals over the last 48 hours have been impressive with Deer Valley topping the list at 37″!

  • Deer Valley: 37″
  • Brighton & Powder Mow: 32″
  • Beaver Mountain: 29″
  • Park City: 28″
  • Solitude & Snowbasin: 19″
  • Snowbird: 18″
  • Alta: 17″

With all the new snowfall in the Wasatch, the avalanche danger continues to be high in the back country.  The Utah Avalanche Center has issued an avalanche warning for high avalanche danger through 6 am Thursday, Jan 12th.

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Utah Avalanche Center Forecast for Salt Lake region. Courtesy: https://utahavalanchecenter.org/advisory/salt-lake

Scattered snow showers are expected to continue overnight with an additional couple of inches falling in the Wasatch.  By Thursday morning the next system is right on our doorstep.  Snow will develop across southern Utah before moving into the Central and Northern Wasatch by the afternoon.

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HRRR Simulated Radar Reflectivity for tonight through tomorrow afternoon. courtesy: weatherbell.com

Snow will continue across the Wasatch through Friday morning before tapering off during the afternoon.  Low density snow will fall Thursday with several inches of powder expected by Friday morning.  Areas in the northern Wasatch will see lesser amounts of snowfall as the storm will centered in central and southern Utah.  Skies will clear out this weekend with excellent weather expected for skiing.

Snowfall Forecast (Tonight – Friday afternoon)

  • Upper Cottonwoods: 6-12″
  • PCMR & Deer Valley: 5-10″
  • Northern Wasatch Resorts: 3-7″