Snowing Now; Moderate Totals Expected.

TL; DR Heavy snow is currently falling in LCC and BCC. Expect snow to taper off throughout the morning before picking up again this afternoon. After a break Thursday morning, more snow is expected on Thursday afternoon into Friday.

Good morning USW skiers and riders. First and foremost, I hope everyone is safe from the earthquake this morning. Perhaps it’s a blessing in disguise that we weren’t all commuting. I-80 and KSLC are currently closed. It’s been quite the week.

Back to the weather. Snow is currently falling in the canyons with Alta picking up 5 inches in the last 3 hours. The snowbird snow cam confirms these totals.

Snow cam courtesy of snowbird.com

Snow totals are harder to find in BCC, but based on this webcam shot at Solitude I’m guessing they have similar totals.

Webcam courtesy of opensnow.com

Short term: Our low pressure center is now just south of San Diego and is currently streaming in moisture from the SSW in narrow bands of precipitation.

GFS 12Z model run courtesy of tropicaltidbits.com
Integrated Vapor Transport courtesy of Center for Western Weather and Water Extremes.

Despite most of the moisture being directed to our southeast, we are still getting lots of moisture here in Utah. As this lows moves east, we will move in and out of different bands of precipitation. Therefore, over the next 48 hours, we will have period of heavy precipitation followed by periods of clouds and sun. Fortunately, this first wave has outperformed the models so there is reason to be optimistic. LCC, which doesn’t normally do well with SSW flow, is keeping up with BCC.

The NAEFS plumes have converged since Julie’s forecast yesterday. Below are the 12z (4 am MST) runs on Monday and Tuesday for Alta-Collins. Initially, the American members were really bullish on this storm and the Canadian members were much more conservative. But yesterday’s run shows all members converging around the mean with much less spread. Notice that the mean is roughly the same for both runs.

NAEFS Plumes for Alta-Collins 12Z March 16th, courtesy of University of Utah
NAEFS Plumes for Alta-Collins 12Z March 17th, courtesy of University of Utah

The NAEFS plumes show a quick 3-5 inches of snow falling between 3-5 pm this evening. On the other hand, the SREF plumes (shown below) show maybe an additional inch of snow. I would expect 2-4 inches of snow in the cottonwoods today before things clear up overnight.

SREF Plumes for Alta-Collins 9Z March 18th, courtesy of University of Utah

An additional wave of snow is expected tomorrow afternoon through Friday morning. Expect another 3-5 inches during this wave.

Long Range: some light snow this weekend maybe amounting to an inch or two, then the pattern gets active through the end of the month. After a boring March so far, strong storms appear on the horizon. So get out and tour now to be ready for the stormy weather ahead (but be sure to check the Utah Avalanche Center for the current conditions).

ECMWF Weeklies 500 mb height anomaly for 00Z March 26th, courtesy of Weather Bell

Thanks for reading!

Tanner Visnick

@telellama

Spring isn’t here quite yet

TL;DR: High uncertainty forecast for snow in the Cottonwoods Wednesday into Thursday. Additional accumulation possible Friday.

What an unfortunate turn of events for resort skiing! Just in time for some snow, too. Let’s hope these closures are only temporary. Luckily, you can still get out and ski the backcountry if that’s your cup of tea.

A closed low pressure system is approaching the Intermountain West as the overall upper-level trough digs south towards Baja California. The graphic below shows how amplified this trough is, which provides the dynamics (and moist southerly flow) for snowfall here in the Wasatch.

Graphic courtesy of Tropical Tidbits.

Precipitation is expected to begin early Wednesday morning, with primarily snow up the canyons, rain in much of the valley, and the chance for mixed precipitation along the benches for this storm. Once the precipitation reaches the Wasatch, freezing levels will hover around bench height for at least much of Wednesday. Expect a brief pause in precipitation Thursday morning before picking up again through Friday morning.

Models are struggling a bit with precipitation totals for this storm. The NAEFS plume (shown below) has a lot of disagreement between members, as you can see by the spread of predicted snow totals. The American (GEFS) members are overall showing higher snow totals than the Canadian (CMCE) members. Based on the uncertainty of the model estimates, I would probably be a bit wary of my forecast, but I’m going to err on the low side of storm totals in the Cottonwoods through Thursday morning since southerly then westerly flow typically isn’t great for the Cottonwoods. We might expect 6-12″ in the Cottonwoods through Thursday morning, but I say this with low confidence.

Graphic courtesy of University of Utah.

If you’re interested, Homewood Mountain Resort by Lake Tahoe has received 79″ at the summit during the current storm. Pretty incredible!
– Julie

Closed low and the tour de West Coast

TL;DR
Pretty cool to watch this closed low amplify off the coast of the PNW the last few days. Current ensemble models show agreement that this system will slide along the western seaboard before ejecting up through the inter-mountain west sometime mid week. Snow likely tonight and mild temperatures until midweek.

Short Term:
This system doesn’t look that exciting; warm, windy, and a few inches of snow in the higher terrain. This event will primarily be driven by flow interaction with terrain as there is not a strong signal of dynamics for the SLV Wasatch Front. Take a look at the time heights from the weather.utah.edu tools:

Some “deeper” moisture through tonight but becoming shallow tomorrow.
SREF and NAEFS plumes show strong disagreement of snow totals:

SREF
NAEFS

So NAEFS is indicating a few inches for the top of Collins with one ensemble member going for 15 inches. For the SREF plumes are more… diverse. What this means that while there is a very small statistical probability for around a foot we are more likely to receive around 4-6 inches of snow overall. Given the lack of dynamics, the lack of strong temperature gradients, and southerly wind, I feel more confident in the half of a foot outcome in select locations with 3-4 inches for most areas. Still enough to get some nice turns tomorrow and Monday.

Long Term:
This closed low is really taking the long way around with GEFS model runs indicating that the center of the low will reach as far as the Catilina Islands by Wednesday. A consequence of this process will be southerly flow impacting the region for the forecast period. These winds, combined with higher clouds lingering overnight, should keep temperatures warm throughout the week until this closed low decides to tour Utah.

Cheers everyone! Thanks for reading, see you in the mountains!
Andy

Hope for the Future

TL;DR: Primarily dry weather and warmer temperatures for the rest of the work week and into the weekend. Next chance for a decent accumulation is Sunday.

Happy Tuesday everyone! I hope you all are spending this beautiful day outside and enjoying the sun; I certainly am! These warm spring temperatures and dry weather will continue to dominate at least through Saturday, except for a weak disturbance bringing a chance of light precipitation to the Wasatch Wednesday evening. Freezing levels remain around or just below crest level for the remainder of the week.

Image courtesy of Snowbird.

The next chance for precipitation starts later on Saturday as an amplified trough moves into Utah. It’s still too far out for snow totals, but you might want to think about getting your work done this week to prepare for potential pow days Sunday and/or early next week. Stay tuned to see how this system pans out!
– Julie

Soupy Refresh

TL; DR 2-6 inches of new snow fell last night with several more inches today. Expect sunny weather in the morning with increasing cloudiness through the afternoon. A weak disturbance will move through on Monday night, dropping a couple of inches in the Wasatch.

Good evening USW readers. I am once again on the road so this will be a quick update. Today the we had steady snowfall in the morning and some spotty showers in the afternoon. Temperatures have remained quite warm and the new snow is creamy. Skies are clearing this evening and we should expect partly cloudy skies and freezing temperatures in the high country (might be a little crusty tomorrow morning).

Tomorrow will be mostly dry before another disturbance moves through tomorrow night. It’ll be soupy in the afternoon with temperatures in the 30s at the resorts and and nearly 60 in the valley. FYI, we tied the record high of 70 at Salt Lake International on Friday afternoon so if you thought it was anomalously warm, it certainly was.

Expect 1-3 inches of new snow Monday night. If the snow today was creamy, then expect the snow on Monday night to be of the cheesecake variety (Bridger Bowl shout out there ;)). Any bit of soft snow at higher elevations (except shaded north facing) will clump up by Tuesday afternoon so get ready for some dense push piles.

A bit more snow on Wednesday night, then we’ll look ahead to the weekend for our next chance for a substantial storm. Think snow!

Tanner Visnick

@telellama

Gusty Saturday, Snowy Sunday

Happy Friday, everyone! If you aren’t lucky enough to be skiing, then I hope you’re able to enjoy this glorious spring-like weather we have today!

Currently, temperatures are in the mid-60s (!!) across the Salt Lake valley. Southerly winds will persist and increase in intensity during the overnight hours and continue through tomorrow. Here’s a look at the current frontal analysis for the US. You can see the low pressure system along the west coast that will be impacting our area this weekend.

https://www.wpc.ncep.noaa.gov//noaa/noaa.gif

Tomorrow, expect widespread, strong winds along the Wasatch front at all elevations. At crest level, southwesterly winds will be sustained around 30 mph with gusts forecasted to exceed 60 mph. If you are skiing tomorrow, be aware of the possibility of suspended operations, especially for exposed lifts or trams/gondolas if winds are too strong. Here’s the NAM 3km forecast of wind speed, gust and direction at Alta Collins

weather.utah.edu

By noon tomorrow, expect mostly cloudy skies along with these strong winds. Precipitation will begin in the overnight hours on Saturday night into Sunday morning.

This system will produce snow in two “bursts”. One early Sunday morning, lasting to the late afternoon, and another Monday evening. Temperatures in the valley will remain several degrees above freezing, so most precipitation will fall as rain at low elevations and snow in the mountains.

Through Monday, we should be looking at a moderate amount of new snow! Deterministic and ensemble model output have converged on a range of total snow accumulations for the Wasatch front. I expect areas like the Cottonwoods to see 8-14″ through Monday. Park City mountains will see significantly less, with about 3-6″ expected. Here’s a forecast graphic for total snowfall through the weekend from the NAM 3km.

www.tropicaltidbits.com

More tomorrow!
-Taylor

Dry til Sunday

TL;DR: High pressure dominates through Saturday – our next disturbance arrives late Saturday into Sunday.

Since we are still several days out from our next chance of precipitation, this forecast will gloss over the details and also get into some other aspects of Utah Ski Weather.

The past few weeks have been miserably dry. So, what does that mean for the state of our snowpack? Check out this daily snow water equivalent percent of normal graphic from the NRCS

https://www.wcc.nrcs.usda.gov/ftpref/gis/images/ut_swepctnormal_update.png

Despite our dry spell, much of Utah is either within the normal SWE range for this date, or even a bit above normal. The only area that is slightly below normal is the Beaver River basin area.

In terms of base depth, resorts like Snowbird in Little Cottonwood Canyon are currently reporting 119″, and nearly 450″ on the season. Not bad! The next few days in the Wasatch will be warm and bluebird. Saturday will begin the transition to a storm day with a cloud deck likely and switch to a southwesterly flow regime.

Here’s the current satellite imagery from GOES West – You can see a ridge and cloud free area over the Western US and a trough that is currently situated south of the Gulf of Alaska.
Unrelated to Utah weather, but looking at the satellite imagery, some interesting stratocumulus can be seen off the coast of the PNW. You can keep up with the latest satellite imagery by checking out https://rammb-slider.cira.colostate.edu/

Looking ahead to the weekend, here’s what the ensembles are predicting for future snow accumulations at Alta Collins

NAEFS ensemble forecast for Alta Collins – weather.utah.edu

Obviously over the next few days, this can and will change, so check back every day for an updated forecast!

Enjoy the beautiful weather!

-Taylor

Ensemble or Deterministic?

A lesson on all of your eggs in one basket…

TL;DR:
This forecast is an excellent example of the pitfalls in trusting one model run (deterministic) vs. a group of model runs to compose an average (Ensemble) outcome… Rest of the week: Warming and clearing skies over the area until Friday! There is a large amount of uncertainty for the end of the weekend/start of the workweek in the forecast…

Short Term (Today through Friday):
Left over moisture from an atmospheric river event in the Pacific Northwest could drop a few flakes over the resorts today (but nothing remotely exciting). Semi-Zonal flow will set up over the area later this evening transitioning to lights winds aloft as high pressure builds fully over the Great Basin by Thursday. By Friday both the Euro and GFS Ensemble models point to a large amplifying upper level trough over the Eastern Pacific. (Thanks TropicalTidbits.com!)

Long Term: Saturday to Wednesday
By Sunday, the models show a splitting of the trough but disagree on the intensity; Euro is showing a significant but weaker disturbance than the GFS Ensemble.  GFS IVT Ensemble and deterministic model runs also paint a different picture on locations of the upper level trough and intensity of moisture transport. Extended forecast is definitely hard to pinpoint.

It is safe to say that both models outcomes suggest that the large trough setting up by Friday will begin to impact the West by the end of the day Sunday. However, we see a vastly different picture from both models which have serious implications on what will happen and how much precipitation we will receive. Here is the EPS and GEFS compared side-by-side again for Tuesday evening. Notice the large differences in the 500mb heights over Utah!

I think that this is a great lesson in the use of Ensemble and Deterministic Forecasting. If you were to only use one deterministic model run you would potentially be led down a path of deception. Never put all of your eggs (trust) into one basket (model run). This pattern will need to be analyzed moving forward. Below is the GFS deterministic run for 12Z today, notice the large difference to the ensemble run above (left side). Primary concerns are location of the closed low off the coast of California and differences between the Euro Ensemble…

I’m going surfing! Later taters. (Thanks for reading)

Bluebird Days Ahead

TL;DR: Whole lotta nothin’ through Saturday as a ridge of high pressure builds in over the western US. The next chance for precipitation looks to come Sunday.

Yesterday we had a splitting trough move through the region that brought some snowfall to the state, but nothing stellar. Since then we have cleared out and the sun is shining.

Short-Term: Nothing much to talk about in the short-term with a ridge of high pressure building over the western US. This will allow for bluebird days and spring-like skiing.

Long-Term: We will remain quiet until Sunday as trough looks to dig down the west coast. Currently looks like this trough will split down the west coast and become a closed low off California. Still too far out to make any snowfall predictions but it looks like some moisture will make it our way.

NAEFS Plumes for Alta Collins (weather.utah.edu)

Make sure to stay tuned for any updates!

Eric

Leap Day Snow!

Hope you all enjoyed an unseasonably warm day in the valley – the pre-storm environment brought in those typical strong southerly winds with a cloud deck blanketing northern Utah.

Forecast for Saturday evening – Monday:

The National Weather Service office in Salt Lake City has issued a Winter Weather Advisory that is currently in effect through Sunday at 10 PM.

Watches, warning and advisories – graphic from weather.gov/slc

This weekend’s disturbance is the result of a splitting trough that will make landfall in Northern California this evening. The southern portion of the split trough will then progress eastward, pushing a cold front through the area late tonight into tomorrow mid-day. Shown below is a GFS forecast of 500 mb heights and mean sea level pressure contours, valid tomorrow around 5pm. The black diagonal lines across Northern Utah represent a pressure gradient that will follow the cold front passage.

GFS forecast 500 mb heights (shaded) and mean sea level pressure (black contours) valid tomorrow at 5 pm. Forecast graphic via tropicaltidbits.com

Following the frontal passage, sub-freezing temperatures will penetrate to the valley floor, resulting in frozen precipitation at all elevations. After the frontal passage, winds gusts should substantially decrease, leaving behind rather quiescent conditions as we move into the afternoon hours. Early morning skiing may be a bit of a challenge with strong winds and potentially low visibility.

The GFS and NAM both agree on the timing of the cold front arrival – this will occur beginning around 5 am tomorrow morning. As the cold front traverses Northern Utah, some mid-level instability could result in periods of heavy snow showers in the mid and high elevations of the Wasatch front. Below shows a time-height forecast of relative humidity (shaded colors), potential temperature (black lines), freezing level (blue line) and instability (red contours). Wind barbs are also shown. Remember, with these plots, time goes from left to right on the x-axis.

NAM 12 km time height cross-section showing forecasted relative humidity, instability, freezing level, and wine at various levels. Plot via weather.utah.edu.

One unique aspect of this storm is that as it progresses, we will not see that predominate northwest wind shift like we do in typical troughs. This is due to the splitting nature of the trough that I mentioned earlier.

This storm isn’t expected to be huge, but it will bring several inches of fresh snow to the Wasatch, which is desperately needed after this dry stretch we have experienced. I feel confident in forecasting a storm total of 6-10″ for the Cottonwoods and 3-5″ for the Park City area.

Not a bad start to March in my opinion.

Enjoy the rest of the weekend!
-Taylor