Storm Early Next Week

This weekend will feature comfortable early season conditions across the entire state.  It’ll generally be partly cloudy throughout the weekend with temperatures moderating to near freezing at the bases by Sunday.  With last weeks huge dump of snow, all resorts are now open with ample terrain.

As we head into early next week, we’re expecting a period of very cold, unsettled weather.  A trough is expected to cross through the region Sunday night and into Monday, followed by a weak shortwave trough.  This storm has been trending drier with time, but a lot of uncertainty exists.  The NAEFS is still forecasting a spread of 5-30 inches for the Upper Cottonwoods.    

The cold may end up being the story of this storm.  Below are the forecasted low temperatures for Wednesday.  We expect it to be well below zero up in the mountains.

Beyond this system early next week, the models continue to show a stormy, unsettled pattern.  Let’s hope another one of these systems goes big !

Coldest Storm of the Season Could Arrive Monday

Mountain areas have seen light snow showers this morning just in time for opening day at Powder Mountain and Snowbasin.  Alta and Solitude will open tomorrow, with Deer Valley opening on Saturday. Snow showers will continue through the early evening before the storm exits our area.  Snowfall accumulations will be on the low side with 1-3″ for most locations, with a few spots picking up 2-5″.

mtspcam
Dec. 1st 10:08 am Mount Superior Mountain Cam. Courtesy of alta.com

State of the Snowpack

The active storm track has allowed for many sites to catch up to near-normal snowpack conditions for this time of the year.  The northern mountains of Utah are still below average, but an active storm track should continue to bring relief to areas below average.

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Dec. 1st Utah Basin Averaged Snow Water Equivalent (SWE). Courtesy of www.wcc.nrcs.usda.gov.

 

Next Storm is on the Horizon

High pressure will build across Utah Saturday and Sunday ahead of the next storm system expected to arrive Monday.  A long wave trough will drop southward out of the Gulf of Alaska Sunday morning before moving into northern Utah Monday afternoon.  This system will likely bring the coldest temperatures of the season this far, but precipitation amounts in the Wasatch remain uncertain at this point in time.  Below is an image of the GFS Ensemble for Monday evening.  The GFS and CMC ensembles have trended further north and east with the storm track while the European model keeps the storm further south and west.  A storm track further south and west would favor higher snowfall amounts in the Wasatch, while a solution further north and east would result in less snowfall across the mountains.

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Monday, Dec. 5th GFS Ensemble 500 mb chart. Courtesy of models.weatherbell.com

 

Due to the uncertainty in the storm track, there is considerable uncertainty in modeled snowfall amounts.  The mountains could see anywhere from 5-25″ with Monday’s system.  For now keep expectations low, but hope for the best!

 

 

Progressive and Cold

Despite what you may have thought from the title, this is not a post about the current political state of our country 😉  Rather, this is the atmospheric pattern we are experiencing.  A much different sentiment, but using the same adjectives.

As Alex mentioned in his post, the Wasatch front has seen some impressive snowfall totals the past few days. Bountiful bench finished with 15″, while Snowbird reported 44″ and PCMR saw 35″. Not a bad way to start the ’16/’17 season.

Wasatch Front Snowfall Totals, valid Tuesday 6 am. wrh.noaa.gov
Wasatch Front Snowfall Totals, valid Tuesday 6 am.    Image: wrh.noaa.gov

Short Term:

Over the next 24 hours, the Wasatch Front will see yet another, albeit quick, shot of snow.  Today, highs are forecasted to reach 35 degrees in the valley before bottoming out to a low of 28 on the first morning of December.

18 Z HRRR: KSLC Meteogram. Image: models.weatherbell.com
18 Z HRRR: KSLC Meteogram.     Image: models.weatherbell.com

Temperatures at crest level (700 mb) will hover between -10 and -12 C through Friday morning, putting us just inside that sweet spot known as the dendritic growth zone.  When these temperatures, optimal for crystal formation, are collocated with a vertical velocities maxima, we see enhanced growth of dendrites.  This is seen in the GFS forecast sounding and 700 mb vertical velocity for 18 Z on Thursday (noon).

Left: GFS point sounding for area max vertical velocity denoted by blue arrow. Right: Simulated vertical velocities at 700 mb. Both images valid Thursday 18 Z. Images: weather.cod.edu
Left: GFS point sounding for area max vertical velocity denoted by blue arrow. Right: Simulated vertical velocities at 700 mb. Both images valid Thursday 18 Z.
Images: weather.cod.edu

Timing:
A weak surface front will move across the area tomorrow mid-day.  Behind the front there will be moist west-northwesterly flow.  Throughout the duration of the event I would suspect the Cottonwood canyons will pick up 3-6″ of fresh snow with 2-4″ in other locations such as PCMR, Pow Mow, etc.

 

Long Range:

The Rossby wave pattern in the Pacific looks promising for continuing this progressive, trough-y, period we are currently loving.  We have seen enhanced cyclogenesis off the Kamchatka Peninsula, helping the shortwave troughs to march across the Pacific ocean.

GFS 500 mb heights valid Tuesday Dec 6, 06 Z. Image: models.weatherbell.com
GFS 500 mb heights valid Tuesday Dec 6, 06 Z.       Image: models.weatherbell.com

The above GFS image is valid for next Tuesday, which is coincidentally the next forecasted big snowfall.  As my synoptic professor back in Oklahoma always said, never underestimate the power of the downstream (or upstream for that matter) ridge.  In this case, it could not be more true.  The trough that will be bringing the impending dump is flanked by two ridges, which are enhancing the trough’s wavelength and intensity.

GFS 500 mb valid 12/6/16 6 Z. Downstream view.
GFS 500 mb valid 12/6/16 6 Z.   CONUS downstream view.

This intense trough will bring frigid temperatures from crest level, all the way down to the valley floor.  Notice the 540 dm line is plunging all the way down to Southern California and NW Arizona.  Early indications show -20 C temperatures at 700 mb.

Should be an interesting week.. Check back everyday for an updated forecast!

Weekend Roundup

What a way to start off the season. After two days of on-and-off (mostly on) snow, ski resorts in the Cottonwoods saw upwards of three and a half feet! The big winner was Eagle Point down in Beaver with a reported 54″ of snow. They had the benefit of being far enough south to do well with the Sunday storm and far enough north to pick up on the action Monday.

After this dumping, I wondered if we’ve started to make up on our deficit for the season. Looking at Snotel data, snow water equivalents in Utah are looking much healthier with sites in the high Wasatch being 80-100% of normal. Much of this storm was localized to Utah, so places to our north are still in the red.

screenshot_20161129_222334

Even though we can no longer complain about having no snow, we are still watching for every flake Mother Nature sends our way. Our next shot comes Thursday (only two days!) as undulations in the offshore ridge Mike mentioned yesterday sends a storm inland. The new, experimental, NAM 3KM model forecasts a band of snowfall moving through the Wasatch midday with possible lake nonsense that evening.

NAM 3KM courtesy WeatherBell
NAM 3KM courtesy WeatherBell

Right now we’re looking at 2-5″ in the mountains–no blockbuster but still fun. Beyond that, there is no bad news in sight. The pattern remains progressive, and there’s a possibility for another storm at the end of the next weekend.

Continuing to Produce…

Hopefully everyone’s been out enjoying what they can of this most recent storm system. Not only has it been snowing hard up in the mountains, the Salt Lake valley has gotten quite the treat as well, especially with some heavy lake effect cells this afternoon!

Snowing hard on the East Bench! 2-4PM MST 11/28
Snowing hard on the East Bench! 2-4PM MST 11/28

The short and sweet of what’s to come: Early evening is likely to see continued heavy precipitation in the mountains associated with one last shortwave moving through, until the flow shifts more northerly and our deep moist layer thins out at mid levels. A narrow but highly amplified ridge builds in at upper levels to our west, forcing the trough out of the region and bringing a break in the precipitation for late Tuesday afternoon through Wednesday. This should make for a beautiful non-storm day of skiing! The ridge will then begin to flatten, with models suggesting a weak disturbance moving through overnight into Thursday.

NAM12 Time-height for SLC, note drying at mid-levels through Wednesday with lingering low-level moisture.
NAM12 Time-height for SLC, note drying at mid-levels through Wednesday with lingering low-level moisture.

The Nitty Gritty: One last shortwave will provide the synoptic scale forcing for precipitation to continue, while localized instability and orographics will allow the mountains to squeeze the last bit of moisture out of the low-levels as mid-levels begin to dry. Lake effect will likely continue to fire overnight, but much to our dismay, as winds come around to the north, much of this snow will fall in the western Salt Lake and Tooele valleys. Much lighter snow showers will continue for the upper Cottonwoods, Northern Wasatch, and Park City areas through Tuesday morning, tapering off throughout the day. It would be reasonable to expect another 8-14” with the higher end of the scale in the Cottonwoods, lower end of the scale in the Northern Wasatch and Park City. This will bring snow totals across the Wasatch up to and well over 3 FEET since Sunday.

Ridging pays a visit...
Ridging pays a visit Wednesday making for a pleasant ski day…
...but soon enough we're back in business.
…but by Thursday we’re back in business.

At first look, the ridge building in over the west coast of North America seems concerning, but each of the forecast models continue to punctuate it with weak disturbances. While there’s no major storm in the near-term forecast, Wednesday night into Thursday should bring a few additional inches of snow along a weak front to freshen things up before the weekend. Models disagree slightly on the timing of the storm, though the trend has been towards snowfall starting later Wednesday night and carrying into Thursday. While it’s too early to narrow down the range, most ensemble members suggest on the order of 2-6” of snow across the Wasatch. The deterministic GFS, always overzealous, suggests the possibility of totals in the 6-10” range, but we’ll just have to wait and see how the models develop this system over the next 48 hours.

Welcome to Nuketown

We are in the midst of a beautiful, classic Wasatch storm cycle. From last night through 6pm this evening (Sunday), our resorts picked up anywhere from 7 to 16 inches of new snow, and much more is on the way.  BIG SNOW will fall Monday morning through Tuesday morning.

 

The deep through of low pressure that brought us our snow last night and today continues to sit over the Mountain West. The trough is situated such that we are getting a nice tap of Pacific moisture and a nice tap of Arctic air…perfect ingredients for lots of cold, dry snow:

 

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The 500mb pattern at 5am Monday, Nov 28th. Note the flow out of the Northwest stretching all the way from Alaska.

The lift, moisture, and cold air associated with this trough will keep the snowfall going over us for the next 2 days, and with each disturbance that moves through that trough, the snowfall rates crank up. Tonight we are between disturbances, so our snowfall rates will slow down a bit, but it will still keep piling up. The next disturbance comes in tomorrow (Monday) morning, and that’s when the real action starts. Snowfall rates will crank up bigtime, with periods of 2″ per hour (or more) snowfall possible. These will be beautiful, fluffy, low-density flakes and will pile up fast. The heaviest snowfall will be from morning through evening on Monday, and then the snowfall will gradually slowdown through the day on Tuesday. The storm should be over by Tuesday night.

This storm won’t be dropping a ton of liquid (1-2″), but with the potential for 20:1 snow-to-liquid ratios, this will be an absolute dump. I’m gonna go for 18-36″ of new snow for the Cottonwoods and the Northern Wasatch. Expect more like 12-24″ for the Park City side.

Next Storm to Arrive Sunday

An active storm track is expected to continue for the next week. Currently, snow water equivalents across the Wasatch are sitting around 30-50% of normal, but help is on the way.  The next storm to enter Utah is currently spinning of the coast of California.  The system will make its way into Utah late Saturday night into Sunday morning.  Snow levels will start rather high (~8,000 feet), before dropping to the valley floor by Sunday afternoon.

rb-animated
GOES-West IR Satellite Imagery (1500 – 2230 UTC Friday, Nov. 25th) showing the storm system off the CA coast. Courtesy of NOAA Satellite and Information Service.

The Canadian, GFS, and ECMWF models are in fairly good agreement with the timing and evolution of the first system impacting Utah Saturday night into Monday morning.  Strong SW flow will develop ahead of a cold front, with mountain showers developing early Sunday morning.  Cold and moist upper levels along with lift associated with a shortwave trough and upper level jet streak will set the stage for heavy snowfall across the mountains Sunday afternoon into Monday morning.

Snow ratios (20:1) will be ideal for powder conditions late Sunday afternoon into Monday morning.  Moist NW flow as seen in cross-section below for the 18 UTC run of the NAM, will create favorable conditions for persistent orographic snowfall in the Upper Cottonwoods. There is also a chance for lake enhancement Sunday evening into Monday morning.

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Friday, Nov. 25th 1800 UTC NAM cross-section over Salt Lake City showing prolonged period of moist NW flow. Courtesy of weather.utah.edu

I suspect this will be a big event in the Upper Cottonwoods with 12-18″ of snow falling by Monday morning.  The Northern Mountains will see 6-12″ with Park City picking up 5-9″.

naefspl_cln2016112512f168
Friday, Nov. 25th 1200 UTC NAEFS downscaled guidance for the Upper Cottonwoods showing the active pattern continuing. Courtesy of weather.utah.edu

Another storm system is expected to move into Utah Monday afternoon. There is still quite a bit of uncertainty as seen above in the 12 UTC NAEFS downscaled guidance, but models are generating anywhere from 15-25″ of snow with the second system.  Models continue to show an active pattern persisting for the next 2-3 weeks, with multiple storm systems continuing to bring snow to the mountains.  Hopefully by next weekend, another host of ski resorts will be able to open.

 

Opening Weekend!

Last night’s quick hitting storm dumped another healthy dose of snow across the Wasatch.  Alta and Snowbird reported 12″, while PCMR ended with 6″.

Next weekend will be the official start of the ski season with Brighton and Brian Head announcing that they will open on Friday and PCMR on Saturday.  Alta is planning on opening on December 2nd, while Snowbird has been teasing us about opening this coming weekend, but has yet to release any official info.

Temperatures will moderate as we head into the weekend before the next system enters the region.  The next system will move in late Saturday night.  There’s still some uncertainty with this system, but it appears that most of the energy will stay to the south of Utah.  With a moist NW flow on Sunday, I still expect most areas of the Wasatch to pick up several inches of snow, especially in the Upper Cottonwoods.

Total QPF from the GFS through 00Z Monday
Total QPF from the GFS through 00Z Monday

Another, more organized system, will impact the region on Monday and Tuesday.  It’s early, but this one has the potential to produce significant snowfall in the mountains.  The long range continues to look active with storm systems crossing into the intermountain west every few days.

Quick Hit before Thanksgiving

A cold front is on its way toward Northern Utah. As of writing this, at 2:30 P.M. MST, the boundary is draped through the Great Salt Lake Desert and up into Eastern Idaho. It has been snowing in the higher elevations there as the precipitation band slowly makes its way southwest.

High clouds to the west possibly showing signs of convection
High clouds to the west possibly showing signs of convection

Current estimates place the precipitation arriving along the Wasatch Front between 4 and 5 this afternoon. It may start as rain in the valley, but it won’t be long before snow makes its way to the low elevations. Snow will last through much of the night and possibly scattered showers will continue into the morning. Let’s take a look at what this storm means for the mountains.

The air is cold enough that all of the precipitation above around 7000 feet will fall as snow. Model guidance suggests that rates will be quite high for this event. First a look at the High Resolution Rapid Refresh model (HRRR) and its solution: it has heavy snow through much of the night.

hrrr_ref_slc_8
Image courtesy WeatherBell

If the HRRR had its way, we would be waking up to a foot of snow in the Upper Cottonwoods and 4-8 inches elsewhere in the mountains. One problem I find with this forecast though is that it includes an unrealistic amount of lake enhancement. Notice the band of heavier snow in the graphic above stretching out from the lake aiming right at the Cottonwoods. The HRRR unfortunately uses a much larger Great Salt Lake than the one of November 2016, and can sometimes overdue the input from that body.

Next lets take a look at the NAM 4KM nest. I immediately took issue with the fact that if this model had its way, it would have been snowing in the mountains by 2 in the afternoon. Anyhow, the simulation has the same idea as the HRRR with heavy snowfall lasting through most of the night in the mountains, but this time without all the lake nonsense.

Image courtesy WeatherBell
Image courtesy WeatherBell

This model produces 14″ in the Upper Cottonwoods and 4-8″ for the rest of the mountains–mostly agreeing with the HRRR on that front.

But these are mere numerical models and serve only as guidance. They show possibilities but are limited. This next graphic shows a plume of possibilities as forecast by the Short Range Ensemble Forecast system. While there is agreement on a period of heavy snow tonight, how much will fall ranges from less than 0.3 ” SWE to over 0.8″ SWE. That’s anywhere from 5″ to over a foot of snow. (For comparison the HRRR and NAM 4KM are showing 1.2″ and 1.6″ SWE).

Still a range of possibilities
Still a range of possibilities

In light of all of this uncertainty, here is my forecast.

For the Upper Cottonwoods: 8-14″

For Park City area: 4-8″

For the Northern Wasatch: 5-10″

More on the way

The forecast for yesterday’s storm went as planned with 9-12 inches for the Upper Cottonwoods. Accumulations were a bit lower at elevations < 8000 feet due to relatively warm temperatures associated with the storm. More important for base building, the storm also delivered high amounts of Snowfall Water Equivalent (SWE) with almost an inch and a half of SWE in the Cottonwoods! Fortunately, the good news continues. Another storm is on tap for tomorrow (Wednesday) afternoon through the evening. This one will be much more of a quick-hitter with snowfall only lasting 6-12 hours in the mountains.

namconus_ref_frzn_swus_fh17-32
Wednesday afternoon – night storm (NAM model reflectivity)

Because of the short duration I’m expecting SWE values around .3″ – .6″. This storm will be colder than the last with snow ratios closer to 15-20:1. Therefore, I think 5-10 inches is a reasonable forecast for the Northern Wasatch. Less favored areas in NW’ly flow like PC will likely fall in the lower end of that range with the Cottonwoods probably closer towards the upper end. Unfortunately, resorts still aren’t open across Northern Utah so you’ll have to get out into the backcountry to enjoy the freshies. Watch out for hidden treasures with the thin snowpack and as always take necessary backcountry precautions for avalanches even if skinning up at resorts. Though danger is low, the first skier triggered avalanche of the season occurred today on the old snow/new snow interface.

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Main Chute – Mt. Baldy (via https://utahavalanchecenter.org/)

Long Term

After a brief period of ridging on Thursday and Friday a trough will be digging across the Western U.S. Right now it looks like we’ll have 2 shots of precipitation with the first coming late Saturday into early Sunday. The trailing wave on Monday into Tuesday is expected to bring even more precipitation. While the details regarding timing are still uncertain, what is certain is that we’re in store for a stormy period and MUCH colder temperatures early next week.