Freshies

Finally. Finally we got a good storm, both in the mountains AND in the valley! So even if you couldn’t make it up to the slopes today, you could at least enjoy the snow in your own front yard.

But, if you did make it up, you know that most resorts in the Wasatch saw almost a foot of new snow.  Here are some totals –
Alta: 14″
Snowbird: 14″
Powder Mountain: 14″
Park City: 9″
Brighton: 8″
Sundance: 4″

Not bad if I do say so myself.  If you can get out there tomorrow, my suspicions are that it will still be some of the best conditions of the season.

Short-Term:
The “storm” we talked about last week that could potentially make an impact on Sunday evening has weakened considerably.  I don’t expect any additional precipitation to occur in the mountains tomorrow evening.

Ridging should build in Monday and persist until our next mid-level trough sweeps through the area Thursday night-Friday morning.  This timing is subject to change over the next several days.

GFS 500 mb valid Friday 5 am models.weatherbell.com
GFS 500 mb valid Friday 5 am models.weatherbell.com

In the mean time, get out there and enjoy the fresh snow!

Your Last Snow-Storm Forecast

Overview: Snow in the SLC area and surrounding mountains beginning by 6PM Friday, lasting through the night, ending late afternoon Saturday. Accumulation estimates range between 2-4 inches in the SLC valley, up to 15-18 in the Cottonwood canyons, with locally higher amounts. More details below.

Pardon the lapsed care and quality in the aesthetics of this post, but I’d like to get to you some hot-off-the-press details of the forecast for this forthcoming snowstorm… Are you pumped yet?

The Forecast Details:

To start, forecast models are still aiming in widely different directions when it comes to snow accumulation estimates. On the other hand, the timings in the most recent model runs seem to be consistent across the board — so I’ll start with that.

Timing

The latest model outputs have been forecasting a slightly earlier frontal passage (~6PM at SLC Airport) as well as a slightly earlier rain-snow changeover for the valley (~7PM). Given these trends, I’d be cautious to run busy errands in the old dodge caravan anytime after 6PM.

forecast
HRRR 1km elevation reflectivity forecast, initialized at 1PM MT, looping through 5PM MT Friday through 1AM MT Saturday. Cold Front passes through SLC Valley toward the beginning of the loop, and precipitation becomes widespread in northern UT toward the end (courtesy tropicaltidbits.com)
Here are more details:

4PM today – by this time light snow in the northern and central Wasatch mountains begins to fill in.

6 – 7 PM today – The cold front will begin to move into SLC Valley, bringing widespread and heavy precipitation. A changeover to snow in the lowlands should occur around 7PM. The front will stall in the valley for some time.

8PM today – By this time, the cold front will begin moving south.

11PM today – We should see widespread and steady snowfall across northern Utah.

8AM Saturday – The end of heaviest accumulations for most areas, however the majority of people will have seen their greatest accumulations earlier in the storm period.

2-5PM Saturday – Snow should clear out of northern Utah sometime in this period. Small local accumulations still possible later.

Accumulations:

There are still great uncertainties in the forecast for specific snowfall amounts. Some models have been more precise than others. Furthermore, many model deterministic outputs are disagreeing with the others. This is probably why many of forecasts you’ve seen have given ranges in accumulation, followed by the words “…with locally higher amounts.” To be cautious, I’m going to imply the same in these estimates:

SLC Valley: 2-4 inches, benches 3-6.

East Slopes (Park City area): 6-10 inches, leaning toward the higher end.

North Wasatch (Snowbasin area): 10-14 inches

Cottonwoods: 15-18 inches …with locally higher amounts

Again, please consider the uncertainties in these estimates, and keep track of the nowcasts, as they become available, before making big plans.

With that, if you can, make sure you take advantage of this storm! Then send us your pictures 🙂

Happy skiing,

-marcel

This Weekend’s Storms Are Snow Joke

DISCLAIMER: LONG POST – SNOW TOTALS ARE AT THE BOTTOM

Ok disregard my cringeworthy snow puns but y’all, I’m not usually one for hype… but this weekend makes me excited.
Partially because it has been a disappointing season thus far.. Rocks and shrubs that are usually buried by this time of the year are still exposed, not to mention many steep slopes with high traffic are a sheet of ice. Hopefully after this weekend we feel like we’re skiing in Utah again.
Also of note, today’s high temperatures are nearly 15 degrees above climatological normal for this time of the year.  You know its bad when this Oklahoma girl doesn’t even need a jacket.

A Quick Summary:
Today’s prefrontal warmth will give way to a cold frontal passage and the possibility for some snow totals to get excited about.  The northwest flow regime will stick around through Saturday.  We are also interested in another weaker disturbance Sunday night into Monday for some additional snowfall in the mountains.

Storm 1 Set-Up:

Tomorrow in the late afternoon hours, the surface front (~23 UTC, or 4 pm MST) will arrive in the Salt Lake Valley, bringing a wind shift to north-northwesterly and falling temperatures. The front wont reach crest level (700 mb) until late Friday night given the frontal structure’s north-westward tilt with height.

NAM BUFR Sounding valid at 23 Z Friday (4 pm) via weather.utah.edu
NAM BUFR Sounding valid at 23 Z Friday (4 pm) via weather.utah.edu

The sounding illustrates what I mean by the front arriving later at the higher elevations. Another thing I want to point out is the box around the “Column TPW” variable.  This is the amount of Total Precipitable Water available in a column of the atmosphere. 12.6 mm is roughly 0.5 inches, which is rather high for this time of year in SLC! According to the Storm Prediction Center’s sounding climatology page, 0.5″ of TPW is in the 95th percentile for January 20 at KSLC.. The good news is, we should have a generous amount of moisture available during this storm.
As advertised, the mountain tops will finally feel the effects of the FROPA around midnight tomorrow.

GFS 700 mb temperature valid 00 Z Saturday via models.weatherbell.com
GFS 700 mb temperature valid 06 Z Saturday via models.weatherbell.com

Expect crest-level temperatures to fall to -11 to -13 by Saturday morning.. These cold temperatures are ideal for dendritic growth, especially when the Wasatch enters the prolonged northwest flow regime as shown by the time height section below

NAM BUFR Time-Height Cross section via weather.utah.edu
NAM BUFR Time-Height Cross section via weather.utah.edu

In my opinion, this is one of the more promising set-ups we have had this season.  The post-frontal northwest flow should continue through Saturday evening.. Free refills anyone?
As a forecaster I also feel as though I should also play the devil’s advocate and discuss limitations with this system. My primary concern is not the moisture availability, but the strength of the flow that will produce this orographic enhancement on Saturday. The Wasatch can surprise, but I’ve been jaded by this year so far.

Storm 1 Snow Totals:
Ensembles like the NAEFS have taken this storm and gone absolutely bonkers with the QPF and snow totals… One member is so out to lunch that it is forecasting 130″ through Tuesday. Remember that when one ensemble member is so high, it skews the ensemble mean as well.  Thus, you can’t always rely on that bold line that is meant to average out all the scenarios produced by the ensemble spread.

NAEFS Downscaled QPF and Snow Totals
NAEFS Downscaled QPF and Snow Totals

For my personal snow totals, I think I am going to back off a bit from Tom’s forecast and go with 10-20″ for the central and northern Wasatch with areas of 2 feet possible if we can get that NW flow really cranking. 8-14″ seems likely for PCMR.

“Storm” 2:
Alright did I exhaust you yet? As has been alluded to in previous forecasts, another weaker disturbance will move into the area on Sunday night into Monday.   Realistically, this won’t amount to much, but beggars can’t be choosers, am I right? We will have a better idea if this comes to fruition in the next day or so.

Happier days are upon us, friends! Enjoy some fresh turns and be thankful you don’t have to use a “sick day” to do so!

-Taylor

Storm Coming

Tomorrow will be warm and windy as southwesterly winds pickup out ahead Friday’s storm system.  A cold front will approach and cross through Utah on Friday and Friday night. The cold front will be associated with much colder temperatures and a period of moderate to heavy precipitation.  Although there is still uncertainty, we expect the cold front to impact the northern Wasatch starting in the early afternoon and southern Wasatch in the evening.

The cold front should slow down as it crosses the region, leading a several-hour long period of widespread precipitation.  Unlike previous systems, the flow will stay moist and northwesterly behind the system through at least Saturday night, leading to on and off snow showers in the mountains.  The time-height section for Alta supports this:

NAMET_ALTA2018011800F084

Snow levels will be at the valley floor for the majority of the storm, so the snow will be light and dry in the mountains. Most NAEFS members produce between 10 and 30 inches of snow at Alta.

NAEFSPL_CLN2018011712F168

On the other hand, the SREF produce between 0.4 and 0.8 inches of precipitation.  Considering that this will be a cold storm with ratios around 20:1 in the mountain, this equates to 8-16 inches of snow.

SREFPL_CLN2018011721F087

Taking all model output into consideration here are my expected totals through midday Sunday:

North, central, and southern Wasatch: 10-20 inches
Areas favor in NW flow (ie, Cottonwoods): 14-24 inches

The next storm enters the region Monday morning, which we’ll have more info on tomorrow.  The long range is finally looking with cool and unsettled weather. That mid-January pattern change we’ve discussed is almost here.

A Weekend Storm Sandwich

As mentioned by both Alex and Marcel in the last couple of posts, we’re looking at a late week storm that has significant potential to bring some deep snow the Wasatch. Before digging into those details, let’s discuss what we can expect for the rest of this work week.

High pressure and associated calm and sunny conditions that we experienced for the holiday weekend will be tracking slightly eastward as a low pressure system moves into the Pacific Northwest on Wednesday. With this, we’ll see southwesterly flow begin to pick up until this system passes into N. Utah sometime Friday.  With this SW flow, expect warm and breezy conditions (especially for the day on Thursday as well as Friday morning).

Our (first) main event will be Friday, when this low pressure system from the Pacific NW is forecast to move into Utah with decent cold air that will drop snow levels to valley floors. Mountain precipitation looks quite pleasant as well, with plume ensemble forecasts from weather.utah.edu putting out a wide variety of QPF ranging from  0.75″ to 2″ at Alta (10-30 inches of snow!) from Friday morning to midday Saturday. We will be sure to update you as Friday gets closer about storm track, timing, intensity and of course snowfall expectations, though.

Fortunately after Friday/Saturday, high pressure doesn’t seem to be modeled to redevelop immediately over the eastern Great Basin. So, we could see some mountain showers continuing through Sunday. Another trough potentially plunges into N. Utah on Monday to sandwich the weekend with storms! With this being almost a week away, I’ll leave out the details, but will just say that the NAEFS downscaled snowfall forecast at weather.utah.edu has over 80% chance of 2 feet of snowfall in the Cottonwoods by covering the period from now until Tuesday morning with these sandwich storms . Keep daydreaming about powder as we head toward the weekend!

Precipitation potential and probabilities covering the next week from weather.utah.edu. Looking snowy!
Precipitation potential and probabilities covering the next week from weather.utah.edu. Looking snowy for the weekend!

 

The Late-Week Winter Weather Looks Good

TLDR: We are warm for the week, and will see a strong cold frontal passage Friday morning (give timing some wiggle room), bringing weather, sizable snowfall, and appropriate winter temperatures to kick off the last third of the month.

The Signs for Snow

Halfway through the first month of 2018 and– while we are trailing behind the Eastern US, the Alps… even Greece (yup) — we have been insinuating over the past few weeks omens for better weather, and will likely see those mid-range predictions materialize later this week.

 

To start, here’s another mid-range prediction for you. Systems will pass later this week and early next week and, along with a late-week cold air injection, will augment our chances for decent pow in the 6-10 day time period.

 


The Weather Forecast Discussion

In a broad sense, there are two “systems” to discuss this week. The first will be a buzzkill for most of you, so I will just graze the surface:

Tuesday (Doozy)

Tuesday night (the 16th) we will see a very weak front pass through the valley. Anticipation in the past few days began after a shortwave feature was poised to bring some amount of mixing into the area early this week. Ultimately, this feature has set up into a weak, moisture-starved disturbance that will probably escape your notice. My thoughts are that we will see some clouds, a midnight breeze, and maybe a flurry or two up high.

Friday

Next, I have some initial thoughts for Friday’s much-talked-about storm that does look very promising. At this point, I’m just going to cover the synoptic set up and leave the mesoscale for later posts this week.

To start, a sharp, positive and widespread vorticity signature indicates that we will see a classic, strong northeasterly frontal system with snowfall periods at all altitudes and across pre- and post-frontal time regimes.

weather ECMWF 500 mbar relative vorticity at 6AM Saturday the 20th. Note strong and uniform vorticity maximum focused across the leading edge of the upper trough--a good set up for a powerful frontal system.
ECMWF 500 mbar relative vorticity at 6AM Saturday the 20th. Note strong and uniform vorticity maximum focused across the leading edge of the upper trough–a good set up for a powerful frontal system (courtesy weather.us)

Next, and importantly, this system is set-up so that it follows an injection of sub-arctic air into our area. Notice that winds will more-or-less follow lines of constant geopotential height, and furthermore that those lines are tilted northerly as the system passes through (see the figure below), meaning that winds will bring us cold air from the north. This is a big plus both after a week of above normal temperatures and months of warm-type frontal passages that kept snowfall uncertainties high through their forecast periods.

weather ECMWF 700 mbar geopotential heights at 6AM Saturday the 20th. Northerly winds moving along geopotential contours (shaded) bring cold air that accompanies the front.
ECMWF 700 mbar geopotential heights at 6AM Saturday the 20th. Northerly winds moving along geopotential contours (shaded) bring cold air that accompanies the front (courtesy weather.us)

Lastly, I’m happy to see signs that a good supply of moisture will extend from the surface up through the 500 millibars level (the latter shown below).

weather ECMWF 500 mbar relative humidity (shaded) at 6 AM Saturday the 20th. Widespread dark-bluegreen colors over northern UT indicate that water vapor is condensing across large regions. The synoptic wave pattern of these features suggest that this system is supported by deep and widespread moisture.
ECMWF 500 mbar relative humidity (shaded) at 6 AM Saturday the 20th. Widespread dark-bluegreen colors over northern UT indicate that water vapor is condensing across a broad area. Additionally, the synoptic-wave-like pattern of these features suggests that this system is supported by deep and widespread moisture (courtesy weather.us)

The Details:

Interestingly, the GFS (not shown in this post) is in good agreement with the Euro’s estimates of strength and timing for this storm. Therefore, I am confident enough to share some first thoughts on the storm details. Keep in mind, the predictions that follow are really just preliminary:

Timing: Frontal passage and maximum precipitation beginning sometime Friday morning, ending later in the day. Still room for error.

Strength: SLC Valley – could see a couple of inches; Park City Base – a couple inches up to maybe a half foot; North Wasatch – several inches up to around a foot or more; Cottonwoods – several inches up to a foot and a half. Preference for snowfall maxima in the cottonwoods given this type of storm.

All in all, give this a few days to settle, but I am ready to gear up for this late week storm.

-marcel

Nice Week Ahead

It was a gorgeous day today. Sunny skies, warm temperatures, and weak winds. It got into the 40s in the Upper Cottonwoods, and the mountains have been all-around welcoming this holiday weekend. The low-elevation snowpack is pitiful, but there’s enough high up to have a good time.

It’ll be cloudy for most of the week. Not dark and gloomy for most of it, just a layer of high clouds that persists under the ridge. Temperatures at mountain-level will be falling through the next few days. The ridge takes a blow on Wednesday as a storm on the 49th parallel brings more precipitation to the Pacific Northwest. Down here it will mostly be a cloud storm with a handful of flurries in the mountains.

Maybe a few flurries Wednesday, maybe a bit more this weekend. Via weather.utah.edu.
Maybe a few flurries Wednesday, maybe a bit more this weekend. Via weather.utah.edu.

Looking forward, there is something interesting for us forecasters to watch next weekend, but in the words of the National Weather Service office here in Salt Lake:

Screenshot_20180114_205043

Blue Bird days ahead

TDLR

Warm temperatures with sunny skies can be expected through the rest of the holiday weekend.  High pressure begins to break down across Utah Wednesday with snowfall potentially returning to mountain resorts.

Short Term Forecast

Sunny skies, light winds, and warm temperatures can be expected Sunday and Monday.  Ridge line temperatures Sunday and Monday afternoon will approach the freezing mark as the upper level ridge becomes centered across Utah.  Shaded northerly aspects should hold up fine with the low sun angles this time of year.

 

gfs_z500a_namer_5
GFS 500 mb geopotential height anomaly for Sunday afternoon. Courtesy of tropicaltidbits.com

Valley inversions will continue to build the next couple of days; however the lack of snow cover should keep the air from getting to gunky.

Extended Forecast

Models continue to suggest the ridge breaking down across Utah next Wednesday as a shortwave trough slams into the ridge.  At this time, models are still all over the place with how much snow could potentially fall Wednesday.  Model ensembles continue to show the potential for a stronger storm system to arrive into Utah on Friday as a broad trough moves across the western U.S.

ecmwf-ens_z500a_namer_7
ECWMF ensemble 500 mb geopotential height anomaly for Friday morning.

The Climate Prediction Center gives central and northern Utah a 60% chance of above normal precipitation during the next 6-10 days.  The pattern is finally setting up in our favor, with multiple storm systems potentially moving into Utah from the northwest in the active northwesterly zonal flow.

610prcp.new
Climate Prediction Center 6-10 day precipitation outlook gives central and northern Utah a 60% chance of seeing above normal precipitation.

-Alex

 

Sunny Daze (and more)

Well, let’s face it – if we can’t have powder for the holiday weekend, we might as well have *absolutely gorgeous* sunny days lined up. This morning we saw lingering snow showers give way to decreasingly cloudy skies as the trough progressed eastward and a ridge begins to build for the next few days.

What this means: expect sunny skies up high  with winds decreasing throughout the day Saturday and remaining relatively light. Ridgeline temps will creep towards the freezing mark, holding steady there for the rest of the weekend. Not ideal temperatures for powder preservation, but shaded aspects should hold up OK. Groomed turns at the resorts should be silky smooth by midday under the bluebird skies and sun.

NAM12 Meteogram for the weekend, highlighting warming temps at Alta Baldy summit, and decreasing winds.
NAM12 Meteogram for the weekend, highlighting warming temps at Alta Baldy summit, and decreasing winds.

Down in the valley models suggest an inversion developing under the subsiding air that comes along with ridging and high pressure, but the lack of an existing cold pool and snow cover, and mixing by light-moderate winds will limit the intensity of the inversion and accumulating pollution. I’d expect values to creep towards moderate by Monday/Tuesday but hopefully the next shortwave trough will keep it from sticking around too long.

Forecast soundings for Sat/Sun/Mon pre-dawn indicating a developing shallow inversion near the surface and warmer air moving in aloft.
NAM12 Forecast soundings for Sat/Sun/Mon pre-dawn indicating a developing shallow inversion near the surface and warmer air moving in aloft.

Long(er) Range

Models bring a weak shortwave trough into the region by Wednesday though keep it pretty fair north and moisture starved. I’m going to shrug this one off for now and focus on the ‘good news,’ a more significant snow producer, out towards next weekend. ECMWF and GFS ensemble forecast mean anomalies both agree on a fairly high-amplitude and broad trough moving in by Friday 1/19. It’d be silly to put numbers on it yet but models suggest a pretty decent moisture stream associated with this system (especially by this year’s standards). We’ll keep watching and updating as time progresses, but we’re hoping for it as much as all of you are!

ECMWF-EPS (Left) and GEFS (Right) ensemble mean 500 mb height anomalies indicating a broad, high amplitude trough moving in to the region for Friday/Saturday next week.
ECMWF-EPS (Left) and GEFS (Right) ensemble mean 500 mb height anomalies indicating a broad, high amplitude trough moving in to the region for Friday/Saturday next week.

More to Come

Overnight Storm

As Peter alluded to in his forecast, a weak storm is currently moving into Northern Utah this evening. While precipitation totals don’t look overly impressive, I’ll continue to take whatever we can get. The best chance for a solid refresher is far Northern Utah (Powder Mountain & Beaver Mountain) where the mid-upper level dynamics associated with this weak shortwave are slightly enhanced.  Totals up there generally look to be in the 2-5″ range and 1-3″ in the mountains closer towards the SLC area.

Short Term

By tomorrow night conditions should begin to clear up making way for perfect weather this holiday weekend. Make sure you get any remaining pow stashes by Saturday because the warmer temperatures will likely nuke anything not north facing. Bluebird conditions should prevail through Monday with unseasonably warm conditions on the slopes (highs in the upper 30s – lower 40s).

Long Term

While the title of this blog may be a little misleading considering we have relatively clear conditions through this weekend…I’m actually optimistic about the long term for the first time this season. Individual storm specifics are still tough to nail down this far out, but I’m expecting opportunities from at least a few storms in the 6-14 day range.

814prcp.new