April Showers

Weekend warriors rejoice, another weekend of good skiing with fresh powder is on tap. A classic Spring storm system is upon us, evident by the strong winds from a tightening pressure gradient and approaching cold front. Other than the occasional brief shower, the bulk of the precipitation will begin moving in overnight (late Friday/early Saturday). An initial shortwave trough will bring the cold front into Northern Utah and it should remain stalled there during the day Saturday. I think the big winners during the day will be the far Northern Wasatch including Beaver Mountain. My one concern is the warm temperatures and high snow levels – Beaver Mountain with a base elevation near 7000 feet will likely be flirting with rain lower mountain. Make sure you bust out your best goretex – it’s going to be a wet one!

ecmwf_precip_06_slc_6
ECMWF forecasted precipitation during the day Saturday
ecmwf_t700_slc_6
ECMWF 700 mb temperatures Saturday

 

 

 

 

 

 

 

 

 

 

Saturday night is when the storm should begin really producing the goods for areas like the Cottonwoods. The meat of the trough will move across Northern Utah and begin to tilt negatively as it moves towards the east. Without getting too much into technicalities this storm will have some pretty good dynamics associated with it. In addition, 700 mb temperatures will crash below -10 C Saturday night. With favorable moisture for a cold, moist NW flow this is combining to be the perfect recipe for a solid Spring powder day on Sunday. For totals I’m expecting 8 – 16 inches ABOVE mid-mountain for the Northern Wasatch. With favorable NW flow I think the Cottonwoods should come out in the 12 – 20 inch range.

NAMET_KSLC2017040712F084
Time height cross section showing frontal passage and moist NW flow

Start getting excited

Alex cautioned us on Monday not to get too hyped up just yet for this weekend’s storm. I’m not quite on the hype train like famously loud and excited storm chaser Reed Timmer, BUT I am start to get excited.

Hype train featuring Reed Timmer and infamous OK Met Mike Morgan. No idea who to credit with this masterpiece.
Hype train featuring Reed Timmer and infamous OK Met Mike Morgan.
No idea who to credit with this masterpiece.

Why am I getting excited? For many days now, multiple weather models and their ensemble systems have been depicting a strong storm with heavy precipitation over Utah for the Saturday-Sunday period. The fact that there has been a long period of similar model solutions for the weekend, with different weather models arriving at this same solution, and their ensemble systems supporting this as a likely outcome…that gives me a good amount of confidence that we can expect a big storm this weekend.

precip
Sat-Sun precipition from the GFS (left) and the ECMWF model (right). Both depict a big event. models.weatherbell.com
Screen Shot 2017-04-05 at 12.53.12 PM
Precipitation output from the ECMWF ensemble members at SLC. Almost all of them are on board with a big event.

The question, however then becomes “what will the snow levels be?” The answer is looking like “all of the above.” They look to start very high on Friday night, lowering through the day Saturday, and then reaching the valley floor by Sunday morning. These types of details will evolve somewhat as the event gets closer, but I think this evolution looks pretty likely.

In the meantime, Thursday looks like a really nice day to be outside, with sunny skies and warm temps. Friday also be warm, but the winds will pick up and light precip will begin to move in, especially later in the day.

 

Don’t Climb Aboard the Weekend Hype Train Just Yet

As some of you might of heard by now, some forecasts are calling for a modest snow event this weekend.  I don’t want to completely curve your excitement for this possibility, BUT it is also important to remain realistic.  Forecasting snowfall in the northern Wasatch is extremely difficult 5-7 days out.  Snowfall in the Wasatch is strongly dependent on moisture availability, flow direction, flow speed, and 700 mb temperatures.  All of these above parameters are dependent on the exact location, trajectory, and strength of the upper level trough as it moves into Utah.  Forecasting the exact location of the upper level trough 5-7 days out is unrealistic, and thus, forecasting exact snowfall 5-7 days out is nearly impossible.

What models can tell us 5-7 days out though is the likelihood for a pattern change.  Model ensembles can show us if the deck of cards is stacked in our favor for potential unsettled weather.  Below is an image of the European Ensemble 500 hPa anomaly (blue to purple colors represent lower pressure while orange colors represent higher pressure), which shows the potential for a longwave trough over the western U.S this weekend.

eps_z500a_noram_23
European Ensemble Mean for 12 UTC (6 am) Sunday morning. Courtesy of weatherbell.com

Before getting to excited, we should investigate the uncertainty within the forecast. Below is an image from the Canadian Ensemble 500 mb heights for Sunday morning.  The black lines represent the mean height field while the red letters represent locations of the upper level trough for each ensemble members.  Where these red letters are closer together, there is a higher confidence in the location of the trough and where they are further apart, there is less confidence.  Notice how the red letters below are far apart across Oregon, Washington, And Idaho?  What this boils down to is there will likely be a trough across the western U.S. this weekend, but there is no way to tell if the trough will dig down into Utah – giving us snowfall and colder temperatures – or merely give northern Utah a glancing blow.

 

2017040312_054_E1_north@america_I_ENSEMBLE_gz@moy_144
Canadian Ensemble Forecasts for April 9th at 12 UTC (6 am). Courtesy of https://weather.gc.ca/ensemble/index_e.html

What’s the bottom line?

We will see a pattern change this weekend with the potential for unsettle weather across northern Utah and we will likely see a storm system impact Utah this weekend, but we can not estimate the exact strength of the storm, and associated snowfall accumulations, at this time.

 

 

We Have a Long Week Ahead of us

It snowed today! A few precious inches fell in the mountains. It was wet stuff with meager 10:1 ratios, but I hope you enjoyed it. It’s all we’re getting for a while. High pressure is going to dominate over the next week, and, while I refuse to rule out the occasional light mountain shower, any decent storm will have to wait till next weekend.

Screenshot_20170402_220651
The reason for the (dry) season

At least we’ll have a couple of relatively cloud-free days in there to enjoy the spring weather.

Warmest March on Record

After an incredible December – February for powder skiing, March was certainly a let down. This March will go down as the warmest on record for Salt Lake City. The low elevation snowpack has been seemingly torched at this point. Fortunately, upper elevation sites above 8000 feet are still fairing pretty well. The losses in snowpack below, however, are quite noticeable. This March also marked one of the wettest on record for SLC, however, the mountains did not reap a lot of those benefits. The warm temperatures meant most of those storms came in with high snow levels, and we even had a few storms that produced more QPF at the airport than in the mountains – bummer.

make_img

I don’t want to be too much of a downer, though, since this season has been great and the best in several years for Northern Utah. The Upper Cottonwoods, for instance, are closing in on 500 inches, and we still have more ski season left! How are things looking this next week?

Unfortunately, the storm for Sunday/Monday has continued to trend weaker in the models and now doesn’t look like much more than a few inches. Dust on crust conditions look likely for the next few days until mid-week when things clear out. This will hopefully soften up snow a bit and maybe even bring about a brief corn cycle if we can stay clear for a few days. The next potential for a “big storm” looks to be next weekend.

It’s certainly spring.

Today was certainly an interesting one out in the Wasatch. If you made it out, chances are you found some of the heavy, wet creamy goodness to be had. While not bad skiing, it’s a pretty clear indicator we’ve moved into springtime snow with limited cold air support. 

NAM Time-height for Salt Lake City, UT
NAM Time-height for Salt Lake City, UT

Looking forward to the weekend: we’re moving into drier conditions for a few days, while an active pattern remains upstream to our west. Warmer temperatures and sunshine should prevail through Sunday, with the next trough digging in to the region for Monday. At the moment models have this event wrapped up pretty early Monday, and the model trend has been weakening. Deterministic output only produces 4-8″ from this little wave. We’ll see how it develops as it comes into range of the higher resolution HRRR on Sunday.

GFS Meteogram into early next week, Alta, UT
GFS Meteogram into early next week, Alta, UT

Sun should work to soften surfaces both days this weekend, making for pretty great skiing. The active pattern appears to continue into early April, so we’ll keep our fingers crossed for just a few more great powder days while we can get them.

Complex System

Showers have entered the region out ahead of our next storm system.  Expect southerly winds to increase as we head into the early evening.  Between 5 and 6 PM I expect a fairly strong cold front to push through the the Salt Lake Valley.  It’ll cross through the northern Wasatch an hour or two before then(3-4 PM) and the southern Wasatch an hour or two after then (7-8 PM).  The time height cross section from the NAM 12-km below highlights this frontal passage nicely:

NAMET_KSLC2017033012F060
NAM-12km time height cross section for SLC

I wouldn’t be surprised to hear a rumble or two of thunder as the front passes through.  Associated with the front will be a band of steady precipitation.  Models are forecasting this band of precip to stall somewhere in Utah as the low pressure system closes off in southern Utah.  Uncertainty remains as to where this will happen – hence why we aren’t confident in snowfall totals.

As we head into Friday winds will shift to easterly, which could lead to very strong winds in the valley.  Periods of precipitation will continue throughout the day tomorrow, but the easterly flow may limit accumulations at resorts on the west side of the Wasatch.  With so many small scale features at play combined with high uncertainty, the high resolution NCAR Ensemble appears to be a useful toll in forecasting snow amounts.  Here is its output for the Upper Cottonwoods:

NCAR Ensemble for Upper Cottonwoods
NCAR Ensemble for Upper Cottonwoods

Accounting for the low snow ratios and uncertainty in this system I am going with 6-12″+ for the Cottonwoods and Northern Wasatch.  This system will sit and spin in southern Utah, providing them with additional snowfall.  I expect totals in the southern Wasatch to range from 10 to 20 inches.

We clear out for this weekend, then another storm early next week.  An active spring pattern looks to continue for the foreseeable future.

Next Storm to Arrive Thursday

Wednesday will offer up mostly clear skies across Utah as a ridge of high pressure builds into the area.  Quality skiing conditions can be expected tomorrow afternoon with light northerly winds around 10-15 mph and base temperatures in the mid to upper-30s.  By Wednesday evening, high clouds will begin to stream into Utah ahead of our next system.

GFSMG_ALTA2017032818F180

GFS Meteogram for the Upper Cottonwoods

Southwest winds will increase Thursday afternoon ahead of a cold front. A few isolated snow showers will be possible before the front arrives. The cold front will arrive Thursday night with a band of moderate to heavy snowfall expected along the cold front.

gfs_mslp_pcpn_frzn_wus_fh0-84
GFS 6-hour precipitation rate and type through Saturday morning

Behind the cold front, winds will shift to the north to the northeast. Snow showers will continue through Friday afternoon before tapering off Saturday morning.

Snowfall Forecast (Thursday PM – Sat AM)

  • Upper Cottonwoods:  12-20″
  • Northern Wasatch: 10-18″
  • PCMR & Deer Valley: 9-15″

Overall confidence in this forecast is lower than normal, as a slight shift in the low pressure center’s position could lead to lower totals. 

Storm, Bluebird, Storm, Bluebird

The past 4 days have followed the pattern of a storm day followed by a bluebird day & tomorrow looks to be no exception. After a lovely bluebird ski day, another storm is on tap for Monday. Right now it looks like snow will begin for the mountains during the morning hours and pickup during the afternoon. It should be a “last chair” kind of day, or for those of you wanting to get out in the backcountry things should be filling in quite nicely for a post-work tour. Of course, as always, refer to the Utah Avalanche Center whenever venturing into the backcountry.

What am I thinking in terms of totals you ask? Well first I want to quickly recap the last couple of storms to impact Northern Utah. Both of these featured more precipitation (albeit of the rain variety) in the valleys than in the mountains! While not unheard of, it’s certainly more common to see the reverse due to orographic enhancement. Unfortunately, both of these events featured weak forcing over the Wasatch and the best upper level dynamics were displaced on 25-50 miles to far to the west. What about this storm? I’d anticipate better orographic enhancement this time around but nothing to write home about. For totals I’m expecting 6-12 inches with the Cottonwoods falling at the upper end of the range.

ecmwf_tsnow_slc_25
ECMWF model forecasted snowfall totals for this week

Thing will clear out Tuesday/Wednesday before yet another storm impacts Northern Utah on Thursday/Friday.

THIS is what Spring weather should be

Yesterday’s storm was quite impressive, and probably came as quite a shock to those of you already in warm-weather mode! Alex’s forecast verified well, as snowfall totals above 7,000ft were generally in the 5-10″ range. This isn’t a super impressive storm by that metric, but Salt Lake airport saw its wettest March day EVER with nearly 2″ of liquid falling. That’s 1/8 of our normal yearly precipitation in a single day! And curiously, <1″ of liquid fell at many sites in the mountains. A particularly strong band of precip set up across the state, and the airport happened to be located under the band.

 

Today is a nice break in the action, with bluebird skies and light winds. I suspect the skiing was pretty good this afternoon before things heated up.

 

becker_00001
The view from Snowbasin this afternoon

Fortunately, this break will be short-lived, and another storm rolls in tomorrow (Sat) morning. It won’t be very cold, or very strong, but it’ll be a nice refresher. Expect 4-8″ at most resorts by Saturday night.

Precipitation Forecast from ECMWF model
Precip forecast through Saturday night from the EC model

The next storm comes Monday, and it looks strong, but quick-hitting. The pattern looks to remain active after that.