Storm to Dump Big Snow in the Wasatch this Weekend

TLDR: Big snow underway as we head into the weekend. It’s another two-punch system with a lot of uncertainty, beginning maybe sometime Friday afternoon, lasting into early Sunday. Most resorts could see a foot or more snowfall, with higher amounts favoring the cottonwoods.

It couldn’t be a better time to dream about the weekend—there’s a lot to unpack for the upcoming storm. So … I’m just going to jump right into it:

The Forecast

General Overview

We’ll see a complicated wave push through between Friday and Sunday this weekend. Complicated, but I think we can break it down to two-ish events. As timelines go…first, the full system pushes south along the Pacific coastline. As it deepens, a smaller wave breaks off, moves east and then northeast across northern UT. That’s Friday.

This is a shortwave
GFS 500 mbar relative vorticity, spanning 11AM MT Thursday to 11AM MT Saturday. This is a wide view of North America, including Alaska and the eastern Pacific. SLC is located below and left of the figure’s center point. Notice the large trough tracking south along the Pacific coast, its axis just passing into Oregon. There’s a small lobe on the system’s eastern side that tracks up through Idaho, Montana, and into SW Canada. That’s Part one. (courtesy

Part two, the main trough, hits perhaps late Saturday night into Sunday.

Part Two
GFS 500 mbar relative vorticity, spanning 11AM MT Saturday to 11PM MT Sunday. See the first figure for further orientation. As the lobe associated with Part One moves off, the main trough begins to swing east into the Rockies, bringing us Part Two. (courtesy

Breaking the system down into two distinct storms makes it easier to understand what is going on, but I don’t think we’ll be able to distinguish the two as it’s happening. It might easily seem like one big, long storm. Nevertheless, establishing the storm’s parts will clarify some of its finer details.


Next, I’ll give you my thoughts on the timing for each storm, followed with their individual strength, ending with preliminary snow totals.


Kickoff: Most ensemble members have snowfall beginning Friday morning in the North Wasatch, afternoon further south. Valleys I think will see similar start times. Still, perhaps moderate uncertainty there—a sizeable amount of notoriously skeptical ensemble members doubt the first punch bringing much, until maybe late Friday night.

Shutdown: End times are even less certain: most ensemble members still predict a shutoff between Saturday morning and Sunday evening. Count on cutoff time changing a bit in the next day or so.


We have low confidence of the strength for each storm over northern UT, and thus a vague idea of overall snow timing. Again, it’s a complicated system.

That said, I’m inclined to trust a weaker first burst and a stronger second storm, and therefore later start times. The latest forecasts seem to trend toward this solution, and we only have about a day to go before the show begins. I think we’ll have a late afternoon Friday kickoff across most of the Wasatch (first north, then south), and a Sunday morning-early afternoon closing.


Most models are cranking over an inch of liquid precip across the northern Wasatch, closer to 1.5” in the Cottonwoods. In terms of snowfall amounts, I’d say pretty good confidence of snow totals exceeding a foot at many resorts, with higher totals favoring the cottonwoods, and locally even higher amounts.

First call…maybe 18-24” snow in the cottonwoods, 12-18” in the north Wasatch, 8-12” in the east slopes. At this point, please be flexible with these amounts.

Whoo—that’s all I can think of. A foot, two feet…either way looks like we’re getting hit pretty nicely. I just want to end by suggesting you prepare to check online for avalanche hazards in case you plan to explore the backcountry. A big snow dump like this can make for issues with the snowpack stability.

But…enjoy, and happy skiing.


Two More Days

In case you didn’t notice with all the excitement, it snowed last night. Parts of the Cottonwoods got an inch, and I woke up to a skiff on the east bench. It’s always nice to have freshly fallen snow on the ground, even if it’s just a trace.

After last night’s system passed, we had partly cloudy skies. Now that the next storm is approaching, they will start to cloud up. Multiband infrared satellite imagery shows a classic comma cloud draped across the far western United States with some high clouds preceding it near northern Nevada/southern Idaho. I could have used imagery from the old GOES-West satellite to get a better angle, but I’m so stoked for the GOES-S launch tomorrow that I’ll stick with GOES-16. Also the details in the loop are gorgeous. Notice all the small, low clouds over the ocean. This is indicative of how insanely cold this storm is.


Likely a surface cold front is underneath where the thickest clouds are in the loop–aka it just came ashore. Before a cold front makes it as far inland as Utah, we’ll have the typical pre-frontal weather that happens here. The wind will blow, and the dust will gather (unless it’s all weighed down by wet right now). This NAM forecast from for mountaintop winds shows rocking gusts from the south starting tomorrow afternoon and continuing into Friday. It won’t really be a good time to be on any exposed ridges. There will also be snow showers Thursday afternoon.

NAM12 00Z 2018-03-01 via
NAM12 00Z 2018-03-01 via

I still can’t get over that gif because it’s so stunning. Like wow. Anyways, the real fun starts Friday afternoon as a cold front finally reaches northern Utah. As per usual, it will come from the northwest and affect the northern Wasatch Front first before moving into Salt Lake and Utah Counties. The timing of the front is somewhat uncertain, but it’s looking more and more like late afternoon. From a meteorological perspective, late afternoon is the most exciting time to have a cold front because then the air mass ahead of the front can warm up during the day. This makes for a storm that packs a wallop, and it often makes for good photos. The timing could fall apart, or it could be cloudy here Friday during the day, so I’m not making any promises. But check the forecast Friday morning and maybe have a camera ready to point northwest.

With the front will come the snow. The way this storm is setting up, however, is that the precipitation band will stall out somewhere near northern Utah. Someone is going to have a good night. The problem is that there is still quite a bit of uncertainty as to who is going to have a bonanza and who is merely going to have a good storm. For example, the 00Z NAM 12 km tonight shows Salt Lake County and the Cottonwoods sitting under heavy precipitation for most of the night. Its forecast would bring a foot of snow to the valley and more to the mountains. However, that model’s 4 km child stalls out the snow band over Box Elder and Cache Counties. That would bring feet to the Wellsville and Bear River Mountains and maybe a foot and a half or so for the Cottonwoods. I’m bringing this up to illustrate the uncertainty that we’re still dealing with two days out.


Above is an ensemble plot of precipitation at Alta for the next few days. The first storm are the showers Thursday afternoon. Those will bring 3-6″ to the Cottonwoods. For the next part of the storm on Friday, the uncertainty increases. The orange lines and blue lines represent ensemble members that use two different “dynamical cores”, or the piece of the weather model that deals with moving air. What’s important is that the two cores will represent the front differently, and it shows in how the ensemble splits. The orange ARW lines show heavy precipitation in the Cottonwoods Friday evening. If you go to the website and click around you’ll see that the NMB members show a spike like that for sites in Weber County, indicating that it positions the frontal precipitation up there Friday night. Then Saturday during the day a precipitation band forms over the Cottonwoods in both models.

Looking across all the models, two different stories emerge. Story A is that a frontal band sets up across far northern Utah near Weber/Box Elder/Cache counties Friday night. Then the band reforms Saturday and pushes south across Salt Lake County and the Cottonwoods. Out of the 00Z models tonight, this story is supported by the European model, NAM 4km, and SREF NMB members. Story B is that a frontal band sets up across Salt Lake and Davis Counties Friday night. Then the band reforms Saturday and gives the Cottonwoods a second heap of snow. Out of the 00Z models tonight, this story is supported by the GFS, NAM 12km, and SREF ARW members. At this point there’s really no way to know what story is right. Hopefully tomorrow will bring some more clarity, and, either way, it’s going to be a good weekend.

Don’t Count your Chickens Before they Hatch


Party cloudy skies with calm winds are expected Wednesday.  Southwesterly winds ramp up Thursday afternoon with snow showers beginning across mountain resorts.  Snow is likely Friday through the weekend with significant accumulations possible. 

Short Term Forecast

Skies will begin to clear out Wednesday afternoon with calm winds and mostly sunny skies expected.  Our next storm system is expected to arrive in Utah Thursday afternoon.  A deep closed low will dig off the coast of the Pacific Northwest Thursday evening into Friday morning.  Southwesterly winds will increase Thursday afternoon with a round of mountain snow showers expected.  Snow shower activity will continue through Friday morning before briefly tapering off ahead of the cold front Friday afternoon.

ECMWF 500 mb ensemble height anomaly for Friday morning. A deep closed low is located just off the coast of the Pacific Northwest. Courtesy of

The main story ahead of the cold front will be strong prefrontal winds on the order of 60-80 mph along ridge lines.  Dust is likely to be kicked up across the deserts in western Utah and will be brought into the Wasatch Front and mountain resorts in the Cottonwoods and surrounding areas.  Along the cold front, there will be the potential for very heavy snowfall as the front lifts an abnormally moist air mass.  The air mass along the frontal boundary is expected to have column integrated water vapor values in the 90-95th percentile for this time of year.  As the front moves into northern Utah, models are suggesting the boundary will stall, allowing for a period of prolonged heavy snowfall.  The main forecast challenge is determining the exact area the boundary will set up.

GFS total column integrated water vapor anomaly for Friday morning.

Currently, ensemble members are in surprisingly good agreement with the frontal boundary stalling out across northern Utah bringing a period of prolonged heavy snowfall to mountain resorts.  As you can see below, the ensemble members are fairly close to each other generating anywhere from 25″ to 45″ of snowfall.  However, there is still plenty of uncertainty with this system.  If the upper level low moves slightly further to the north or west, the boundary could set up to our west or north, leaving the Wasatch high and dry.

NAEFS ensemble precipitation and snowfall in the Upper Cottonwoods. Courtesy of

For now keep monitoring the latest forecasts as there is the potential for one of the biggest snow storms of the year Thursday through Sunday morning.

Long Term Forecast

High pressure will return to the area late Sunday into early next week with mostly sunny skies and warmer temperatures expected.


Changes in the weather…

An important component of forecasting is keeping track of how the model forecasts evolve over time. These trends can be imperative to an accurate forecast, and can also help explain a bust. In the case of the significant mid-week storm we were expecting, models have backed off significantly. Largely, this is due to observed conditions not stacking up to modeled conditions, and the models use the observations to adjust and inform the next forecast.

We’re still likely to get some snow, but totals have been cut back quite a bit as the best dynamics are now much further north than the central Wasatch. If there was one figure to sum up my thinking right now, it’s the following:

ECMWF Salt Lake City QPF dProg/dt
ECMWF QPF dProg/dt for Salt Lake City

To explain what we’re looking at – from the top down, the forecast becomes more recent with the bottom row initialized this morning and the top row initialized 120 hours prior. From left to right is 30 hours ago (verification) to 240 hours into the future. The numbers are the precip totals up to that hour, with green < .5″ water, blues < 1″ water, and yellow/orange < 1.5″ water.

What’s important: the midweek storm has been trending drier, from once ~.5″ water to now < 0.1″. Keeping in mind this is a global model that often under-forecasts orographic precip, we are still expecting some snow up high tonight/tomorrow but 1-4″ seems about it.

Next, the weekend storm: what once looked to be a potent system producing over 1″ of water in the valley has weakened quite a bit in the forecasts, and we see this reflected in the QPF trends. There has been a steady decline over the recent ECMWF runs which seems to be leveling out around ~0.5″. This is still far out enough that we could see these numbers vary significantly in the next few runs, so not all hope is lost yet. For the sake of completeness, I’ll include the GFS forecast, which began much lower than the ECMWF and has been trending upward towards the ~0.6″ mark.

GFS QPF dProg/dt for Salt Lake City
GFS QPF dProg/dt for Salt Lake City

Either way, tomorrow will be snowy with a little fluff on top for a refresh, and I have high hopes for another stellar weekend of skiing. Either way, it seems appreciable snow totals are likely for the mountains by Sunday morning. We’ll keep you up to date as the models keep rolling in!


The Hits Keep Coming

After all that beautiful low-density powder we had yesterday, the atmosphere gave us a quick break this morning. As I write this around 3pm though, the storm track is quickly reloading. Clouds are thickening up and snowflakes are starting to fall with our next system moving in. And it won’t be the only storm this week…there are at least 2 more lined up behind it! Here’s the breakdown:

Time-height digram from the 12Z GFS model for the upcoming week. The hits keep coming!

Storm # 1 (Sat pm-Sun am)

Snow showers will pick up overnight, with cold temperatures (single digits at the resorts) and more low-density blower powder. The models don’t show this system producing a ton of liquid (0.2-0.6″ of water), but snow-liquid ratios will be high (potentially 20:1) and there is a period of cold northwest flow that will benefit the Cottonwoods. The high-resolution models are also going for a period of lake-effect snow overnight tonight that may add a couple more inches for them as well. With that in mind, I’ll go with 6-12″ of snow for the Cottonwood resorts, with 4-8″ of snow elsewhere.

Screen Shot 2018-02-24 at 3.55.06 PM
Precip amounts from the 12Z run of the ECMWF model for Storm #1

Storm #2 (Mon am-Wed am) 

This systems looks a bit warmer than those we’ve had lately, but still with snow levels at or near the valley floors. It also looks to meander around us for 48 hours, which is good in that it increases the time for snowfall to stack up, but bad in that this increases the uncertainty we have in where and how much snow will fall. Hopefully Trey will have a first stab at snowfall totals for this one tomorrow.

Storm #3 (Thur-Sun)

The uncertainty in the details really increases looking this far out, but it looks pretty likely that we’ll have a storm in this period. It also looks like it could be a good one.

Another Good Storm

It has been quite a good storm today. The roads in the valleys (sans benches) have been clear for the most part, but the snow has been piling up in the mountains. Alta reported 8″ by 4 PM, and it’s still falling (as of 4). The sensor at Alta-Collins picked up 0.4″ of snow water equivalent, which would mean a healthy 20:1 snow ratio. Not quite white smoke, but definitely still good powder.

There are two storms on the immediate horizon. We get a break tonight and through most of the day tomorrow. It should get windier as the day goes on and the clouds will thicken before the next round of snow starts late in the day. There’s a chance for some pre-frontal snow, and the northern Wasatch have a somewhat higher chance of taking advantage of that.

Once the sun goes down snow will be widespread in the mountains, though there is a chance it will be showery in nature. The models have been predicting snowfall totals in the mountains similar to today’s storm, though the fact that it will be a night storm will make roads messier. I’m forecasting 3-5″ in most of the mountains and 5-8″ in the Cottonwoods.

The next storm will be Monday, and, as the image below shows, how it will behave is not yet determined. This ensemble of models shows how with today’s storm (on the far left) and Saturday’s storm all the lines are close together and there is not much known uncertainty. But for Monday’s storm there’s a wide range of known possibilities, and, of course, a large fraction of possible storm outcomes fall outside the ensemble range. This ensemble is predicting anywhere from 0″  to 25″ Sunday night through Monday with a mean of about 10″. I’m hoping it’s a good one to keep up this snowy pattern.


Great Skiing Ahead

It took until late February, but we’re finally in a typical, winter-like pattern. Over the next week the region will be impacted by small to moderate cold storms every couple days.  In my experience, this kind of pattern produces some of the best ski conditions.

The first system is currently moving into the region.  Snow will develop tonight and continue through the day tomorrow. The steady, mostly light snow will add up to a general 3-6 inches across the Wasatch with 7 or 8 inches possible in the Cottonwoods.

We’ll have a break for about 24 hours before the next system enters the region Saturday afternoon.  Total snowfall from this storm should be similar to that of tomorrow’s  storm.  The SREF below is generally in line with what I’m expecting for the next two systems.


As I stated, the active weather should continue into next, as advertised by the NAEFS:


Enjoy the skiing!

Bursts of Snow

Some of the coldest temperatures of the winter have nestled into the Intermountain West over the last 24 hours as our deep weekend storm exited the region. Fortunately, the cooler temps are here to stay for the next several days, and we are expected to see consecutive bursts of snow through the weekend. Finally, it’s feeling like winter!

The somewhat northerly trajectory of the storm track that we experienced last weekend – bringing fluffy snow and cold temperatures- is still persisting. The next bouts of moisture and instability will take similar tracks to our previous storms as we head into the final weekend of what is known as meteorological winter for the northern hemisphere (December 1 -February 28). We are looking at at least two quick hitting storms through Sunday. I’ll mainly focus on the first one that is looking to move into northern Utah on Thursday afternoon.

Somewhat moist south to southwesterly winds will pop up some clouds throughout the day Thursday, especially over the mountains. Light snow is possible tomorrow, but the main accumulations should start in the late afternoon/evening hours as moisture deepens through advection into the lower levels. This should increase snowfall across the mountains overnight and into Friday morning and even allow for some light snow to make it to valley floors, thanks to the cold airmass enveloping us.

A weak cold front early on Friday morning is looking to pass through, switching our wind directions to more northwesterly and bringing in slightly cooler air, which could allow for some more orographic enhancement for locations favored by NW flow (Cottonwoods). The slightly cooler air could also add to the atmospheric instability and kick up some lake effect on Friday morning. Here is a NAM-12km time height section showing some of these features:

Time height section showing 1) Crest level S/SW flow during the day Thursday, 2) Deepening moisture into the evening hours, 3) Wind shift to NW and low level moisture that may lead to additional accumulations from lake effect
Time height section showing 1) Crest level S/SW flow during the day Thursday, 2) Deepening moisture into the evening hours, 3) Wind shift to NW and low level moisture that may lead to additional accumulations from lake effect or enhancement

Through the end of the day Friday, here’s what I’m thinking for snowfall totals:

Park City Resorts: 3-6″

Northern Wasatch Resorts: 2-5″

Cottonwoods: 5-10″*

*the usual “with locally higher amounts” pertains

So, a nice refresh to the snowpack ahead of the weekend is to be expected. Additionally, you can see on the above time height section that more snow is headed our way for Saturday/Sunday. We have potential for some nice accumulations from that storm too! It’s a good time to wax those skis and boards and prepare for another fun weekend in the Wasatch!



Cold Stormy Week Ahead

TLDR: In short, the general large-scale setup through mid next week favors frequent cold frontal systems through Northern Utah. It seems that the week will end with a couple moderate orographically-enhanced (high-elevation) precipitation events. More events are likely through next Wednesday.

Hey guys! Given yesterday’s great wrap up of the cold and snowy weekend, I’ll focus mainly on the late-week forecast for this post.

First, a quick recap.

The Recap

As filling as the President’s day storm was, snow-lovers might credit the strength of the storm’s cold front for our big snow, rather than orographic (terrain-induced) effects. As rankings go, this was the 2nd largest snowfall this season at Salt Lake City Airport. In comparison, this doesn’t even make the top 5 storms at Alta-Collins this year. The minimal difference in snowfall between upper and lower elevations tells me that there was minimal orographic-enhancement in the highlands.

The storm left behind lingering lake-effect precipitation (see Taylor’s post for details) and cold temperatures. Tomorrow morning, temperatures could rival some of the coldest temperatures we’ve seen this season (14 degrees F at SLC airport occurred in late December 2017).

cold air mass
GFS 2m temperature anomaly 5PM Friday, February 23, 2018 (blues and dark purples indicate anomalously cold air near the surface). (courtesy

Furthermore, we seem to be in an isolated period of cold weather and frequent cold frontal systems. Why the sudden change after warm temperatures and few snow storms?

It does have much to do with the Pacific ridge, in two ways: First, the big guy drifted west quite a bit and is currently being held in its position. Why? I wouldn’t be able to answer that, not without wandering into mysterious theory land. Storms traveling eastward will avoid this ridge, moving up and over, then straight down to the western US. In contrast, earlier this month the ridge was further east, pushed storms past us to our northeast, and brought some love to the midwest and northeastern US. Second, the entire continent is under the influence of high amplitude waves. This means that both the ridge to our west and the trough to our east are digging deeply north and south, thus shuttling either very cold arctic air (into western US) or very warm tropical air (eastern US). See the map below for a visualization.

Cold Snowy Set-up
GFS 500 mbar heights (black solid) and relative vorticity (shaded) over North America at 11 AM Tuesday Feb 20th 2018. Note the large amplitude trough axis cutting through UT, and a large amplitude ridge axis far into the Pacific. Labeled are the center of this ridge (“H”), the current storm track (red arrows), and potential late week systems (circled in blue). (courtesy

The Forecast

If we maintain this setup, and with some luck, we can anticipate seeing more cold and snowy weather over the next few days. Here’s what the forecast looks like:

I’m seeing at least three events before next Monday, all varying in strength. Furthermore, at least one could be moderately orographically-enhanced. Finally, each system would be cold enough to bring snow to the valley floor.

Wednesday night into Thursday

A weak shortwave (moderate confidence) seems to be a conditionally unstable prefrontal event, and as result should be enhanced as it pushes into the mountains. It’s a weak system, but I think we will see at least a few inches in most ski resorts.


A cold front will pass through, bringing a few inches of snow (moderate confidence). I think we will see a minimal difference in snowfall between low and high elevations with this storm. I don’t think this will outperform last weekend’s cold front.

Saturday Night into Sunday

Another weak shortwave could pass through during this timeframe (low confidence).

In combination, between Wednesday and Friday, ski resorts might see another 5 to 10 inches of snow (moderate confidence), with locally lower or higher amounts. In short, it’s one of a select few times this year we could expect frequent bursts of pow in the mountains. Enjoy!

Also stay tuned this week as we narrow down the details for each storm. In particular, check Wednesday night-Thursday snowfall forecasts in tomorrow’s post.

Happy skiing,


Bonus Time

I think it’s safe to say this storm has not disappointed in terms of producing copious snowfall across the Wasatch Front.
Storm Totals (so far):
Alta: 19″
Snowbird: 20″
PCMR: 14″
Solitude: 15″
PowMow: 12″
Brighton: 16″
While the main trough has moved off to the west and on to Colorado, we’re still in a position to get a few more inches, courtesy of that cranking northwest flow and our friend the Great Salt Lake.

Despite the KMTX radar taking a holiday right along with everyone in the state of Utah, the HRRR is still producing a nice lake band this evening. As the flow backs to westerly, the enhancement from the lake will move north.

HRRR simulated reflectivity.
HRRR simulated reflectivity.

For those of you who are unfamiliar with lake effect storms, many atmospheric ingredients must be just right for snowfall to be enhanced by a large body of water (GSL in our case). Here are a few things to consider:
1. Instability – The temperature difference (lapse rate) between the lake surface and 700 mb must be large enough to ensure that the boundary layer is unstable.
2. Moisture: Boundary layer must still have sufficient moisture in order to produce precipitation
3. Wind Direction: When the wind direction is oriented parallel to the lakes longest axis, the enhancement of precipitation will be greatest.

For lake enhancement in the Salt Lake Valley and Cottonwoods, we want that northwesterly wind to do its thing.  Northern valleys will fare better from lake effect when the wind shifts back to westerly.
So hows it looking for us?
Since this system was very cold, 700 mb temperatures are forecasted to be anywhere between -18 to -22 degrees C this evening into tomorrow morning.  This will create a ~25 degree C temperature difference between the lake surface and 700 mb. This means lapse rates will be around 7C/km, creating an unstable environment (warm surface air will rise and cool).
We also will be saturated through the depth of the boundary layer (air temperature ~= dew point temperature).
Finally, the flow will be out of the northwest with speeds of around 16-18 kt, persisting until around midnight when the flow will begin to turn to a more westerly component. This will mean that the Northern Wasatch will have their turn at some lake enhancement as well.

18 UTC NAM Forecast Sounding valid 10p -
18 UTC NAM Forecast Sounding valid 10p –

For the timing of the lake effect processes, we are looking at late evening into the overnight hours for NW flow and enhancement in the SL Valley/Cottonwoods. Early morning looks best for Ogden and the Northern Wasatch.  If all goes according to plan, I wouldn’t be surprised if the Cottonwoods got an extra 2-5″ and maybe a dusting in the valley.
Given the fickle nature of this atmospheric process, the stakes are higher and the possibility for a let down is definitely greater than with a typical forecast.   But this is why we call it “Bonus Time”! This weekend has already been awesome with all the snow thats fallen, this is just the icing on the cake!

Enjoy, friends!