Hundred Inches

It started snowing early last night in the mountains, and it’s dropped 13″ thus far in the Cottonwoods. For the first time this season, Alta-Collins has reached 100″ of snow depth. Snowbird also is reporting 100″.  It’s nice to finally be in the triple digits. Chances are it will keep snowing in the mountains through the end of the day, and I expect another 3-6″, giving a storm total in the neighborhood of 20″. These spring storms sure can produce.

Sunnyside Webcam via Alta
Sunnyside Webcam via Alta

After this storm winds down, we’ll have a rather quiet week. Showers are possible in the evenings several days, especially Sunday and Tuesday. But by and large it’ll be a great week to get out there. We have all this fresh snow, it should be mostly cloudy for the week, and mountaintop temperatures should stay below freezing at least until Wednesday. Perfect weather for the students on spring break.

Peaking ahead into the longer-term, Friday looks like a good time. Many models are producing around 2″ of water, most of which would fall as snow in the mountains. Right now the GFS weather model is producing an atmospheric river set-up, but a lot of pieces have to fall into place before we can determine what’s actually going to happen. It’ll be something to watch in between trips into the mountains this week.

Another weekend (and spring break!) storm

Sometimes it seems like the best way to get a big storm around here is for one of us to skip town… That certainly seems to be the case this weekend, with a handful of us taking advantage of spring break at the U to explore new places. For those sticking around, this storm should be a treat.

Snowfall will likely hold off until late Saturday morning, with the HRRR producing not much more than light snow showers overnight. For those that enjoy storm skiing, Saturday should get better as the day goes on. The main slug of moisture should come through in the early evening, with an intense period of precipitation that will likely be short-lived. Most models wrap up steady precipitation by Sunday morning around when resorts open. Snow showers are likely to continue on and off Sunday morning, ending in the afternoon.

NAM 12km Time-Height
NAM 12km Time-Height

Models have backed off on the amount of water associated with this system, and we are seeing a consensus around .8” of water for the central to northern Wasatch. With the predominant flow direction out of the SW, I don’t expect impressive enhancement over the Cottonwoods. Big, Little, and the Park City ridgeline should all see totals over 6 inches, with about half as much at the Park City base. Max of around 12” likely at the highest elevations at the head of the cottonwoods. Should some strong convection develop, lucky areas in a bullseye may see an inch or two more.

NAM 12km Meteogram at Alta, UT
NAM 12km Meteogram at Alta, UT

For those always thinking ahead, a few inches is possible into/through Monday.

Enjoy it for me!


March Showers

Some pretty impressive numbers in terms of the liquid water equivalent (SWE) from this storm – 1.8 inches of water at Alta but only 12 inches of snow. This is an average ratio around 7:1 (snowfall:water)…think Sierra Cement. I wasn’t able to sample the goods personally, but I bet it’s actually skiing quite well being right-side up. The high amount of water also means that any crust underneath should be totally covered.

Short Term

Additional light accumulations this evening/overnight should help keep the snow fresh for tomorrow morning, but I wouldn’t expect too much more (1-3 inches). Snow showers should clear out overnight giving way to slightly warmer and drier conditions by tomorrow.

The next storm should begin moving across our area by Saturday afternoon. The GFS has been trending more towards a splitting system with the brunt of the precipitation to the north and south of Northern Utah. The European does show slightly more precipitation, but for right now I’ll take a stab and go with 3-6 inches Saturday afternoon to Sunday morning. Hopefully the models will shift just a tad, and these totals will be upped a little in tomorrow’s forecast. Regardless, the skiing should be good, and a nice change of pace from the Spring skiing we had earlier this week.

Latest GFS model: Saturday - Sunday storm splits
Latest GFS model: Saturday – Sunday storm splits

Long Term

Conditions should clear out as temperatures gradually warm early next week. The next potential storm appears to be mid-late next week, though models have been struggling with the timing.


As I write this around 10pm, it is nuking in the Wasatch! Not by snowfall amount though, but by liquid equivalent. Rain or very dense snow is falling at most sites, meaning that although many sites have already received >1″ of water, snowfall totals are maybe 6″. That’s some serious concrete, but it should cover the tracks well.

Snowbasin snow stake is lookin good!

Fortunately temperatures are dropping with the passage of a cold front a few hours ago, and the snow density should drop accordingly. Snow levels are also dropping, and should get down to the benches by the morning. Precipitation will continue through the day tomorrow, beginning to taper off toward the evening. That leaves us with quite a while to stack up some more snow, which means we will easily hit the snowfall numbers Taylor forecasted, and should likely go even higher than her 16″. Wooohoo!

Looking out further, it looks like another round of precip Friday night into Saturday. Enjoy!

Known Unknowns: Spring Snow Forecasting In the Wasatch

This week, we will transition from our warm, spring-like weather to the cold, overcast, late winter feels of Utah. The synoptic pattern is becoming more active again, which will bring several rounds of precipitation to both the valley and mountains. Forecast uncertainties exist, but it will snow, and hopefully a lot.

Forecasting for the next week made me think a lot about the words of Donald Rumsfeld (and Jim Steenburgh, because he loves this quote):
“As we know, there are known knowns; there are things we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – the one’s we don’t know we don’t know”

So let’s break this down into what we know and what we don’t know.
Known knowns“:  Several short-wave troughs will impact our area from Wednesday through Sunday. These short-wave troughs will bring colder temperatures and precipitation from the valley floor to the mountain tops.  Despite the colder temperatures, weekday snowfall will likely be confined to the high elevations of the Wasatch due to elevated freezing levels.
Known Unknowns“: Timing of each of the tough passages. We have a general idea of the Wednesday – Thursday storm, but as we progress into the weekend, confidence is much lower.  We also know that forecasting snowfall totals (especially around the bases of the resorts) will be tricky. The rest of the post will be devoted to explaining what we know and discussing what we know we don’t know.  As the week progresses, these known unknowns will become more clear.

Short Term Forecast (Tuesday – Friday):

Today (Tuesday) expect increasing cloud cover with temperatures reaching the mid- to low-60’s in the valley.
Tomorrow (Wednesday), strong southerly winds will prevail ahead of the main trough axis, moderating valley temperatures and keeping freezing levels high.  A few isolated convective snow showers are possible at crest level during the day tomorrow. Showers will extend to the valley floor in the late evening and overnight hours as a shortwave embedded within the larger trough axis quickly moves through our area.  Freezing levels are not expected to drop much overnight, resulting in rain at the resort bases and below.

NAM 12km Time-height cross-section -
NAM 12km Time-height cross-section –

Thursday afternoon into the early evening, a shortwave ejecting from the main trough will move through the area. This will finally bring freezing levels to the valley floor as the flow shifts from southerly to more westerly.  Snow will continue through Friday mid-day with accumulations possible down to the valley floor.
Remember that the timing on the freezing level dropping/shift to NW flow may change in the next day or so.. Hence the known unknowns we touched on at the beginning of the post.  Tomorrow we will have a better handle on when to expect precipitation to start, what kind you will see at what elevation, and a more educated guess of how much.
From what we know now: Given the prolonged exposure to the potent available moisture, as well as the instability at crest level, I will forecast that the Cottonwood resorts will see 8-16″ of new snow by Friday.  Look for locally higher amounts in areas favored in the northwest flow regime.

Screen Shot 2018-03-13 at 11.09.04 AM

Long Term (Through the weekend):
This weekend we will have yet another chance for wintry precip in the mountains. The low spinning off to our west will slowly make its way into our area.  Again, timing is uncertain, but model forecasts like our odds of having a powder day on Sunday.  I wont even take a stab at what these totals could be, but enjoy the NAEFS output of liquid and snow to fuel your Tuesday daydreams.




Models Predict Weak Chance for Snow Next Week, After a Warm Weekend

This weekend is that time to accept the warmer weather and blue skies that hint at spring; I think there are times when that can be exactly what you need in day’s ski…still, that’s as far as I’m going to go excusing mother earth, who is letting the weather escape us this week. I see some powder in most models forecasts but it’s unclear and looks kind of weak.

Before I explain, I’ll start with a quick summary of the weather this weekend.

This Weekend

If you’re in Northern UT, you’ve noticed that it’s warm and the sky was clear all day. The warmth is here to stay for a few days, but clouds will move in beginning around 7PM and stick around through the night. These clouds are associated with a system that is bringing mostly rain to southwest UT.

We’ve been under a weak ridge that has maintained mild temperatures late last week, and will continue the pattern this next week. The ridge won’t stay without a fight…two fights.

A shortwave trough passes through this weekend and splits its energy to our north and our south. Southern Utah takes the cake with the southern piece of energy, although only high elevations will see any snow. Forcing is weaker to our north, and it is especially weak over the rest of Utah, so neither areas will see any more than clouds tonight.

The Powder

The next chance for powder in the Wasatch occurs around Wednesday this week. It’s a weak system and only a deserves a quick blurb in my opinion.

A shallow upper-level trough comes into view Tuesday morning and passes east-southeast from the northern Pacific coast of the US. Both the American (GFS) and the European (ECMWF) global models have a weak shortwave feature spin off and pass just north of Utah. The gif below shows the GFS’s deterministic (one possibility) solution for this shortwave’s trajectory.

model 3- to 5- day forecast solution (GFS)
GFS models 500 hPa relative vorticity (shaded) gif valid 11AM MT Tuesday – 11PM MT Wednesday. Note the slow-moving long-wave trough in the Pacific, and some positive vorticity features that move across the western US (courtesy

Beyond this timeframe, the global model solutions diverge. The Euro deepens the trough, then shuffles the system into the continent and weakens it substantially. The GFS solution starts with a weaker system that quickly moves east as it continues to weaken. These are 7-10 day forecasts, and my point is that models don’t easily make sense of the weather in that timeframe and beyond. I’m interested to see what that trough decides to do as we get closer to next weekend. Stay tuned this week!

In summary, we have warm weather for the next few days, a chance for snow on Wednesday, and an interesting set-up to look out for next weekend.


Get it while you can

Man, what a weekend. Yesterday and today were probably the best snow conditions of the year, with storm totals finally tapering off over 2 feet for the upper Cottonwoods, cold dry powder, and a snowpack deep enough to cover most of the rocks.

Get it while you can though, cause a warming trend starts tomorrow (Tuesday) and there aren’t any more good storms lined up in the near future. You can see this below in the time-height diagram from today’s 12Z run of the GFS below:

Screen Shot 2018-03-05 at 7.09.58 PM
Time-height cross section from the GFS model

Highs today were in the upper teens/lower 20s in the mountains, but they will rise into the upper 20s on Tuesday, and the 30s on Wednesday and Thursday. There is a slight cool down and a weak storm forecasted for Thur night/Fri, but the Euro model disagrees with this, delaying any action until late weekend. You can see this in the precip plot below for SLC:

Screen Shot 2018-03-05 at 7.13.50 PM


Hopefully these model solutions trend a bit wetter, which is certainly possible that far out. Until then, enjoy the great snow!



A Deep Sunday (And Free Refills!)

A brief recap and thoughts for this evening – 

Late Saturday night the highly anticipated front finally moved through the Salt Lake Valley, and brought with it copious amounts of snow for all elevations. While all resorts in the central Wasatch faired well, Little Cottonwood canyon was the obvious winner with storm totals of 20”+ since yesterday afternoon.
Here are two of the highest reports I’ve seen:
Alta-Collins Snow Stake (via MesoWest): 21”
Snowbird: 22”
As expected, when powder days occur over the weekend, the traffic becomes a real problem, especially up Big and Little Cottonwood. This morning, if you waited for the canyons to open and sat in the long line of cars, it probably took you several hours to reach your destination. I think its safe to say it was worth the wait, though!

The upper-level low associated with this storm system will linger over the intermountain west through this evening. Some remnant vorticity coupled with strong upward motion should produce some additional snowfall in the higher elevations this evening and into the overnight hours. This vertical motion will result in some crest-level (and higher) instability, resulting in snow showers that could be convective in nature. Think isolated, heavy snow showers rather than a widespread frontal band like we saw last night. Its likely that the upper elevations of the central Wasatch could see an additional 3-5 inches through tomorrow morning, especially the areas favored in northwest flow.

NAM 12Z time-height cross-section via
NAM 12Z time-height cross-section via

After the departure of this trough, a ridge builds in, bringing sunshine and warming temperatures for your work week. A rather quiescent forecast after the exciting weekend we just had.

In the mean time, get out there and enjoy improved mountain conditions and pleasant bluebird days at your favorite resort!

Snow tonight…Finally!

This storm has been a major headache to forecast.  There has been considerable uncertainty over the last few days as to where the front would stall out.  Initially, it looked like it might stall over the Wasatch and produce huge snow totals.  Then Thursday night and Friday the model consensus began to indicate that the front would make it to the SLC and then retrograde back to northwest Utah.  As I type this, the front is still stalled out in northwest Utah.  This evening it will finally begin to progress to the east.  Around midnight it’ll reach the Wasatch, which is when snow will begin to fall in earnest (we have high confidence in this).

Snow will continue, heavy at times, through tomorrow night as shown by the HRRR:


By 9AM tomorrow, I’m expecting a general 8-16 inches across the Wasatch.  A moist, NW flow will continue throughout the day tomorrow.  Storm totals should range from 15-25 inches in the mountains, with up to 30 inches in the Cottonwoods.  Enjoy the storm!

In Like a Lion

TGIF! Winds are whipping across much of the state today ahead of a storm that could potentially be the largest snowmaker of the season so far. A cold front is strengthening across the Great Salt Lake as we speak, and will be entering the Salt Lake Valley this afternoon. As Marcel mentioned yesterday, this weekend will feature a one-two punch of snowfall, the first being this afternoon/evening, and the second starting midday Saturday. While I don’t think it will necessarily stop snowing in the mountains between the two major storm components, the second one is definitely stronger.

Current surface conditions show the southerly prefrontal winds over the Salt Lake Valley with a surface cold front over the lake which is headed in our direction. Here’s what it looks like on Mesowest. Note the wind shift around Antelope Island and colder temperatures to the northwest.

1:30 PM surface conditions from Mesowest
1:30 PM surface conditions from Mesowest

And here what the strengthening front looks like from above – note the clouds moving SE across the lake.

Past 12 frames of COD GOES-16 imagery  as of 1:30 PM (
Past 12 frames of COD GOES-16 imagery as of 1:30 PM (

This afternoon will be exciting in terms of the frontal passage and the start of snow for the weekend, but snowfall by Saturday morning will be small compared to what is to come Saturday evening and overnight into Sunday. I won’t be super detailed, but Saturday afternoon is when the main portion of the low pressure system moves across the area and really pumps up snowfall rates! Here’s what you can expect as you head to the mountains on Saturday morning as well as the projected snow amounts for the entire weekend. You might want to dig out your snorkel for the Cottonwoods on Sunday.

Forecast snow totals through Saturday morning:

  • Cottonwoods: 4-8″
  • Northern Wasatch Mtns: 6-12″
  • Park City Resorts: 3-6″

Forecast storm snow totals through Sunday evening:

  • Cottonwoods: 20-30″
  • Northern Wasatch Mtns: 18-24″
  • Park City Resorts: 10-20″

As always, locally higher amounts are possible. What a treat for our first weekend in March. So as the saying goes, March will be “in like a lion”,  but I’m hoping it isn’t “out like a lamb” and that we get some more great storms this month! Have a great weekend!