Change Can’t Come Soon Enough

TLDR: 

A Weak cold front passes Mon night into Tue morning with maybe 1” of mountain snow.  The better chance for snow is early Wed throughout Wed.  There’s decent uncertainty with the Wed storm and totals range from 3” to 12+” as of now, so check back as we get closer.

DETAILS:

Conditions are rather miserable along the Wasatch Front but much better in the mountains.  Temperatures today for the most part were a bit warmer in the valleys vs. mountains but that will change for tomorrow (Mon) as most mountain sites will be slightly warmer than the valleys.  Skies will be partly cloudy becoming mostly cloudy by afternoon.  So, head to the mountains if you need a break from the pollution etc. in the valley (just take a bus or carpool).

A relatively dry cold front will move through the area early Tue morning with a chance of maybe 1” of snow with cloudy and windy conditions the rest of Tue.

Some light snow is possible overnight Tue-Wed as a better storm approaches and arrives early Wed with precipitation through much of the day.  This fast-moving storm will be accompanied by windy conditions, but snow amounts from the different forecast models and ensemble members span a wide spread as of this writing.  The graphic Alex posted yesterday hasn’t changed much so depending on the storm moisture and trajectory, we could see 2-6” or 8-14”.  Below are the SREF ensemble members to give an idea of the spread and likely precipitation accumulations.  Check back tomorrow to see if models and ensembles begin to converge on a solution.

usw_pic

LONG RANGE:

High pressure will build back in Thu-Fri with a storm beginning to impact the west on Sat, but this far out the Sat storm appears to deteriorate by the time it hits northern UT.

-TKW

Colder Tonight

Not very much has been happening this weekend weather-wise. A shot of cold air moved through the mountains, and temperatures are dropping from near-melting to well below freezing tonight. Alta Base reached up to 32°F this afternoon, but it will plummet down into the teens and maybe single digits overnight. But the winds have been calm, and it’s been pretty dark with some clouds and long midwinter nights.

The cold won’t last long though as warm moves in in the next few days ahead of the next storm. By the end of the day Sunday the resorts will be flirting with the melting line, and by Monday temperatures should be above 32°F in the afternoon. The warmth will be accompanied by clearer skies and even calmer winds (and thickening pollution in the urban area). Later in the day Monday high clouds will move in from the north as the midweek storm approaches Utah.

The next storm will be a two-parter. The first part will be Tuesday, but it won’t bring more than clouds and some flurries. The second part is a fast-moving storm bringing cold air and snow to northern Utah. To show the current state of thinking about this storm, I’d like to draw attention to the graph below showing a few dozen model simulations of precipitation in the Cottonwoods. Each line represents one ensemble member’s accumulated precipitation/snowfall, and all of the thick lines are ensemble means of one kind or another.

Modeled Potential Precipitation at Alta this week, via University of Utah Dept. of Atmospheric Sciences
Modeled Potential Precipitation at Alta this week, via University of Utah Dept. of Atmospheric Sciences

Notice how the means don’t have very many actual model lines near them. That shows that there are really two dominant possibilities of what could happen. One is represented by all the model lines grouped together at the bottom in the  1-6″ range. In that scenario the storm stays mainly to our north. The other possibility is that northern Utah takes a direct hit, and those model lines cluster around 12-16″ (with some outliers going higher).

Right now I’m leaning towards the higher solution, but it is too early to really say much of anything. This storm would be Wednesday, and today is just Saturday. In the meantime we get to enjoy what we have and hope the snowmakers are taking advantage of tonight’s chill.

East coast kind of day

Well, today certainly felt like I was skiing back home. I’m not entirely sure if I mean that in a positive way but being raised an east coast skier certainly makes it easier to put up with rugged snow conditions. The sun over the past few days has done its work, crusting exposed southerly slopes, and its absence today kept the resort groomers pretty firm.

Alta Webcam Friday Afternoon (12/7)
Alta Webcam Friday Afternoon (12/7)

The mountains may receive just a trace of snow overnight tonight before the ridge begins to dominate the synoptic setup and the tap shuts off. That’s not to say the column is devoid of moisture, but there’s not much to make it productive, and drier air filtering in at mid to upper levels will quickly dominate. A stubborn, shallow, broken cloud layer will likely stick around throughout the better part of Saturday, beginning to clear out in the early evening and overnight. By Sunday, subsidence under the building ridge just upstream dominates, and temperatures will warm under sunny skies. The ridge is evident in both the 500 (not shown) and 700 mb (shown below) flow fields, with the axis more or less to our west early Sunday. The lack of white shading indicates low 700 mb relative humidity, helping to prevent any cloud development.

GFS 700 mb streamlines (showing wind/flow pattern) and relative humidity (shaded)
GFS 700 mb streamlines (showing wind/flow pattern) and relative humidity (shaded) at 5AM MT Sunday 12/9

If you’ve lived here long enough, you know ridging in the winter time commonly comes with surface high pressure and strong temperature inversions, capping the valley air and allowing pollutants to accumulate. As Taylor previously indicated, these conditions will likely worsen in the valley through the weekend and into early next week until we get a significant trough passage to help mix out the stable layer and cold air pooled within the valley. Please, do your best to reduce emissions by carpooling and other environmentally conscious decisions. “What you burn is what you breathe!”


Ok, ok, I know you all want to hear about the next storm. It’s still too far out to even hint at total accumulations, but let’s see what we’re working with. Spaghetti plots (aptly named) are a great way to help visualize model uncertainty. The trough that is expected to pass through the region on Tuesday is present in most of the GEFS members, with a few suggesting the development of a closed low over central California. The model mean develops a fairly shallow trough that is a little too far to the north to be a big producer for us here in Utah. The trough does continue to amplify (strengthen) as it moves through and off to our east on Wednesday, but it is a case of too little too late, it seems. A second, slightly more amplified trough enters the region late Wednesday and makes its passage on Thursday, bringing the potential for a more significant dose of mountain snow.

GEFS Ensemble 500 mb heights showing the uncertainty associated with the amplitude of the trough passing through on Tuesday.
GEFS Ensemble 500 mb heights showing the uncertainty associated with the amplitude of the trough passing through on Tuesday.

With that framework in mind, yes, we can take a (cautious) look at the plumes to summarize the outcome of the ensemble forecast (leaving out a lot of in-between detail here).

NAEFS (GEFS+CMCE) ensemble plumes showing QPF and Snow through Thursday.
NAEFS (GEFS+CMCE) ensemble plumes for upper BCC highlighting the spread in QPF and Snow through Thursday.

While the model mean can be helpful, it can hide a lot of the story. As a consequence of the more northerly track in the GEFS, most members are constrained to less than 0.6” of water accumulated during the Tuesday-Thursday period. A few optimistic GEFS and CMCE members go high, but we will likely see those solutions drop out in the coming days. Too soon to say much more.

-Mike

Channel Your Inner Clark Griswold

TLDR: Tonight into early tomorrow, a quick moving system will graze the southern portion of the state. This system could result in a few inches of high elevation snow and light low elevation rain in the southern third of the state. Don’t expect much in terms of accumulations in our neck of the woods. A ridge builds in for the weekend.  Our next chance of unsettled weather arrives next Tuesday.


Sunny skies and a building inversion are whats on tap for this weekend.. Not ideal, but perhaps time to get into the holiday spirit. With only 19 days til Christmas, this quiet weather pattern might be a good excuse to drag out those decorations and channel a festive mindset more like Clark Griswold and less like the Grinch (I know no snow = no fun, but we can all try, right?).

tenor

 

Short Term Forecast (Thursday Evening – Saturday Morning):
In the overnight hours, an upper-level trough will make its way across the southern portion of Utah en route to wreak havoc on the southern plains and eastern third of the U.S.  Compared to the forecasted impacts for the rest of the country, this will be essentially a non-event for us folks in Utah give the current lack of moisture in the western U.S. Below is a forecast of available moisture in the atmosphere.  Note the greys and browns over Utah, showing very dry air, while the brighter colors over Texas show an airmass with potent moisture advancing into the southern plains.

18Z GFS Precipitable water valid Friday 5 am MST
18Z GFS Precipitable water forecast. Valid Friday 5 am MST (via models.weatherbell.com)

Winter storm advisories (purple-shaded counties) and watches (dark blue-shaded counties) cover the southern plains in anticipation of the low interacting with a moist airmass originating from the Gulf of Mexico. Flood watches have also been issued for southeast Texas where temperatures will remain above freezing throughout the duration of the event.

Current weather alerts via weather.gov
Current weather alerts (via weather.gov)

In comparison, we are looking at light precipitation across southern Utah.  Given the track of the progressing upper-level low, there won’t be much (if anything) in the way of precipitation for the northern portions of the state. Ski areas in southwestern Utah, like Brian Head, will likely pick up 3-6″ of new snow from the advancing system.  Rain at lower elevations will be light to moderate through the morning. The 18Z GFS total precipitation solution is showing measurable precipitation forecasted for the Cottonwoods, but I think that is relatively unrealistic.  I think 0-2″ is a reasonable expectation through Friday.

18 Z GFS Total Precipitation through Saturday at 5 am (via models.weatherbell.com)
18 Z GFS Total Precipitation through Saturday at 5 am (via models.weatherbell.com)

3-5 Day Forecast (Saturday – Tuesday):
Over the weekend, quiescent weather will prevail, but air quality is likely to deteriorate. The combination of snow cover, cold surface temperatures, low wind, and low sun angle will aid in the development of a dreaded temperature inversion, which will result in a build up of pollutants in the surrounding valleys. The air quality is expected to be poor enough by Saturday that sensitive groups (asthmatics, eldery, etc.) could be impacted, as forecasted by the Utah Department of Environmental Quality

Salt Lake Valley air quality forecast (via air.utah.gov)
Salt Lake Valley air quality forecast (via air.utah.gov)

Luckily, the inversions rarely impact the high elevations, so get up to the mountains and go ski the excellent early season conditions.

Our next chance of unsettled weather arrives on Tuesday which should not only flush out the valley pollutants, but drop some new snow on the mountains! Enjoy a bluebird weekend!

– Taylor

Settled weather moves in

TLDR: Low level moisture will linger through late week with mostly cloudy conditions and very light mountain snow accumulations (slightly more snow for southern Utah/Brian Head). Then, settled weather moves in over the weekend with sunny, bluebird days for the mountains and valley haze as high pressure builds in. This ridged pattern looks to dominate over our area for awhile until possibly next week Tuesday when models indicate a possible trough making its way through Utah.


TODAY

Ok so it’s been an interesting past couple of weeks, wouldn’t you say? Several systems have come through Utah, providing us with plenty of mountain snow for most of our resorts. And just this morning, we had a band of snow move through northern Utah associated with a mid level deformation axis extending from an upper level low off the coast of California. This produced an additional 1-2″ of snow across the upper Cottonwoods and Park City ski area, with little to no accumulations elsewhere.

Webcam at Park City Mountain Resort's Crescent Ridge at 3:00 PM MST
Webcam at Park City Mountain Resort’s Crescent Ridge at 3:00 PM MST. Image courtesy of parkcitymountain.com

Throughout the day, it’s been cloudy with low level moisture and very light low level winds as promised by the GFS time-height forecast chart Lucas shared yesterday. Above is an eastward facing webcam image from Park City Mountain Resort’s Crescent Ridge this afternoon showing pleasant but cloudy conditions at the mountain. Below is a southward facing webcam time lapse from the University of Utah’s William Browning Building (chpc.utah.edu) this afternoon, showing a steady stream of mid-upper level moisture flowing from out of the southwest ahead of that upper level low off the California coast. Note the valley haze and periods of low level moisture condensing into low stratus clouds over the Salt Lake Valley.


Thursday – Friday

We’ll be stuck in somewhat zonal (west to east) flow over the next couple of days in northern Utah as the low pressure system currently just off the California coast slides well to our south and east. So, expect cloudy conditions with maybe a snow shower or two in the northern Utah mountain resorts during this time, but don’t expect to see much in the way of accumulation. However, in southern Utah things should be a bit more interesting as shortwaves ahead of that low pressure system should be able to draw more moisture into that region. Brian Head should see increasing snow shower activity Thursday afternoon and evening, with the bulk of snow activity occurring Thursday night into Friday morning, winding down by Friday evening. Expect 2-3″ of snow Thursday through Friday evening.

THE WEEKEND!

As a ridge builds in from the west, expect the middle and upper level moisture to move out, and sunny skies to make their way in over Utah. While beautiful blue bird conditions should exist for the mountain resorts this weekend, valley haze associated with trapped moisture and particulate matter (…pollution) will pay us a pretty lengthy visit as a low level inversion (temperatures increasing with height) sets in. Below is a forecast sounding from weathernerds.org showing a weak inversion Saturday morning. Unfortunately, we could see some valley low stratus/fog associated with the inversion this go around, especially Sunday through Monday. Great excuse to get up to the mountains and ski under near perfect conditions!

Weathernerds 12z 5 Dec GFS forecast sounding valid Saturday morning at 12Z (5 am MST) over Salt Lake City. Note the low level inversion, where the red line indicates warming with height from the surface (850 hPa) to approximately 800 hPa (~6,500 ft above sea level). You can tell this is an inversion by the way the red line is tilted slightly to the right compared with the light brown lines (temperatures) going from bottom left to top right. Image courtesy of  weathernerds.org by Matt Onderlinde.

Early Next Week

High pressure should stick around until about Tuesday next week when a trough looks like it could make its into northern Utah. Right now the ECMWF has this as a rather strong, compact wave that would definitely break up the inversion and likely provide the mountains and valleys with precipitation. Below is the ECMWF 500 hPa relative vorticity, height and streamline forecast for 18Z 11 Dec (11 am MST next Tuesday morning) where it shows this trough entering into northern Utah with strong relative vorticity values and cyclonic flow.

ecmwf_z500_vort_west_26
12Z 5 Dec ECMWF 500 hPa relative vorticity, height and streamline forecast for 18Z 11 Dec (11 am MST next Tuesday morning). Image courtesy of models.weatherbell.com

While we wait to see what happens with the potential next system on Tuesday, stay out of the valley smog and enjoy mountain sun and snow this weekend!

-Pete

Early sunsets and late-week moisture

Temperatures started off chilly all across the region this morning thanks to a combination of recent snow cover, clear skies, and cold air advection in the wake of our weekend storm. A view of minimum temperatures since midnight from MesoWest shows many of our mountainous areas near or below zero degrees Fahrenheit, with some especially cool observations well below zero of -11 F in the northern part of Snyderville Basin near Kimball Junction,  -7 F  at Cardiff in Big Cottonwood Canyon, and -8 F at Trial Lake in the Uinta Mountains. The famously cold Peter Sinks dipped to -34 F overnight.

Minimum temperatures (F) since midnight across the Central Wasatch and Eastern Uintas. (mesowest.utah.edu).
Minimum temperatures (F) since midnight across the Central Wasatch and Eastern Uintas. (mesowest.utah.edu).

As we approach the northern hemisphere winter solstice later this month, days are becoming shorter and nights are becoming longer, however, we get to experience our earliest sunsets of the year over the next several days with sundown just before 5:00pm MST. You might ask: “Why is our earliest sunset several days before the winter solstice?” It has to do with the tilt of the earth and how time is kept, and is nicely summarized here. The same goes with our latest sunrise, which occurs several days after the winter solstice in the beginning of January.

Salt Lake City sunrise and sunset times from timeanddate.com. Our earliest sunsets of the year are this week.
Salt Lake City sunrise and sunset times from timeanddate.com. Our earliest sunsets of the year are this week. Explore more at: Time and Date.

____________________________________________

Short Range Forecast (Wednesday – Friday)

While the temperatures were frigid this morning a rebound will occur starting tomorrow – especially for the higher terrain in the region.  The storm system impacting southern California at present time will eject warmer and moister air into the region from the southwest during the morning hours tomorrow. This should allow for some nice orographic precipitation to pop up over the mountains resulting in a bit of light snow. However, don’t expect much in terms of snowfall – maybe up to a couple of inches during the day tomorrow for our mountains. Some more moisture looks like it will be in place during the day on Thursday, but it’ll be still somewhat unexciting (maybe up to another couple inches) as the brunt of the storm passes well to our south. Drying out will start to occur for the weekend along with intensification of inversion conditions.

GFS time-height section for the rest of the week. Expect more moist/cloudy conditions for the remainder of the work week, with clearing for the weekend and intensifying inversion conditions. (weather.utah.edu)
GFS time-height section for the rest of the week. Expect more moist/cloudy conditions for the remainder of the work week, with clearing for the weekend and intensifying inversion conditions.
(weather.utah.edu)

__________________________________________

Weekend and beyond

Beyond our weak surges of moisture during the rest of the week, calm weather will be the case for the weekend and into next week.  Potential for a more active weather period begins midweek next week around the 11th/12th of December, as seen below in the GFS ensemble viewer from wetterzentrale.de. Enjoy the great early-season conditions under the sun this weekend!

Lucas

Sunshine and Powder

As this crazy storm cycle winds down, we get to enjoy some December sun for a bit. The Cottonwood ski resorts are reporting 9-15″ over the weekend, and more showers fell this morning adding to the total. Now high pressure has built in and the sun has come out in the valley. We’ll get to enjoy another day of sunshine tomorrow before the clouds come in again.

Scattered clouds over Utah with clear skies upstream
Scattered clouds over Utah with clear skies upstream. GOES-East imagery via RAMMB/CIRA

The next storm system is similar to some of the ones we saw last week but weaker. A storm is approaching California from the west, and it will bring significant rainfall to parts of the southwest. There will also be precipitation at the boundary between this moist storm air and cold air that moved in with the last storm. Unfortunately, this boundary will be to our north, so the best snowfall totals will go to the Bear River Mountains. Down here it’ll start some showers in the mountains to keep things fresh and then move on. Not that places further north will get very much–just a few inches. At the very least this storm should help stir up the stagnant air a bit. The graphic below shows how relatively moist the atmosphere will be Wednesday afternoon, and the snow will be where the moisture is.

GFS Model PWAT with hand-drawn circle showing where greatest chances for snow is
GFS Model PWAT with hand-drawn circle showing where greatest chances for snow is. Via WeatherBell

After Wednesday, there will be a few more days of clouds and light showers as the storm system passes to our south. Then high pressure builds in for the weekend again and we’ll get some more December sunshine.

Early Season Treat

Yesterday began with a traffic-heavy trip up the canyon as droves of powder-hungry skiers and snowboards made the pilgrimage for one of the first true sunny powder days of the year. The long trip up gave us a chance to chat and reflect on how the season has been shaping up so far.

For one, we’ve got a decent early start as compared to the past two water years with just over 6” of SWE at the Brighton SNOTEL site (2017: 4”; 2018: 2.5”), and just a hair over the 1981-2010 median value (see below). Coverage is rapidly improving, and anecdotally, at the end of the day, we couldn’t seem to remember making turns this good until January last season! Waking up to valley snowfall today was the icing on the cake to tie up a wonderful weekend.

Brighton SNOTEL: 2019 (Current) Water Year
Brighton SNOTEL: 2019 (Current) Water Year
Brighton SNOTEL: 2018 Water Year
Brighton SNOTEL: 2018 Water Year
Brighton SNOTEL: 2017 Water Year
Brighton SNOTEL: 2017 Water Year

As I write this forecast, light-to-moderate snowfall continues across the valley and in the mountains, while the radar struggles to paint a clear picture of conditions in the region today.  Some areas of the valley, including the airport, have reported up to 0.3” of water since Saturday evening, while Alta Collins is reporting 0.18”. The likely shallow nature of the precipitation and weak large-scale forcing are contributing to this scenario of limited orographic enhancement, and even an ‘upside-down’ setup with a valley precipitation maximum. A weak meso-vortex is evident in the analysis of mid-level winds for northern Utah (and in the radar loop shown below), and this circulation is in part what is driving the continued lift and precipitation in the region (see a slightly more in-depth write-up on Jim Steenburgh’s blog at http://wasatchweatherweenies.blogspot.com/).

HRRR Simulated Radar Reflectivity through the next 18 hours. Note the tight cyclonic (counter-clockwise) circulation associated with the meso-vortex overhead of northern Utah.
HRRR Simulated Radar Reflectivity through the next 18 hours. Note the tight cyclonic (counter-clockwise) circulation associated with the meso-vortex overhead of northern Utah.

As the pattern progresses the upper-level trough to our east and build in a weak ridge to the southwest, we’ll see the snow become more showery in nature overnight and into Monday, with drier air throughout the column and clouds beginning to break up by Monday night. In favorable areas of high terrain throughout the Wasatch, decent accumulations are expected overnight, with a maximum of 0.2-0.4” of water (translating to 4-8” of cold, low density snow) expected in the upper cottonwoods. The HRRR does seem to taper off more quickly than the SREF and NAM, but I do think we’ll see numbers within the middle of the above range.

SREF Forecast through the near-term period highlighting a spread of 0.2-0.4" SWE likely for the upper Cottonwoods.
SREF Forecast plumes through the near-term period highlighting a spread of 0.2-0.4″ SWE likely for the upper Cottonwoods.

Monday and Tuesday should provide absolutely banner early season days on snow for the mid-week ski crowd, and excellent backcountry skiing for those with the skills, gear, and group to travel in appropriate terrain (always remember to check the Utah Avalanche Center forecast)! Cold temperatures will persist all the way to the valley floor, helping with powder preservation.

GFS Northern Hemisphere Dynamic Tropopause Pressure: 81-hour outlook highlighting a highly amplified and progressive pattern continuing for the mid-range forecast period.
GFS Northern Hemisphere Dynamic Tropopause Pressure: 81-hour outlook highlighting a highly amplified and progressive wave pattern continuing for the mid-range forecast period.

For those hungry for more, a weak upper-level trough may produce some snow showers by Wednesday – though the ensemble plumes suggest extremely limited accumulations through the period. Models suggest upper-level ridging will dominate, and thus any shortwave trough will exist under generally unfavorable conditions for appreciable snowfall. Have no fear! Though the week ahead looks relatively dry, the pattern remains progressive in the models for as far as we can reliably see.

Alright December, Let’s See What Ya Got

TLDR: A cold storm system will move into the area this evening, potentially dropping a foot of new snow in the Cottonwoods and the central Wasatch. Snow will continue through tomorrow.. Free refills anyone?? Ridging builds in by mid-week, with blue bird conditions on deck for next weekend.


Today marks the first day of the last month of 2018, and so far it looks like December is not going to be disappointing.  The lifts at Solitude started spinning today, and the snow keeps on falling. The last storm that crossed northern Utah left behind 8-14″ of the good stuff at most resorts.  These early season powder days are what dreams are made of. Luckily, we have more of that on the way.

Also, check out this eye-candy that one of our MesoWest cameras captured today on the Bonneville Salt Flats.  Snow-capped mountains reflecting off the water that pooled on the Salt Flats from our most recent storm.. Absolutely stunning!

Picture captured by a MesoWest camera on the Bonneville Salt Flats mesowest.utah.edu
Picture captured by a MesoWest camera on the Bonneville Salt Flats mesowest.utah.edu

Tonight – Monday: A cold trough originating from the Pacific will make its way into the Intermountain region tonight, bringing colder temperatures and snowfall from the mountain tops all the way to the valley floor.  The surface low pressure center will pass to our south, which will result in Northern Utah missing out on most of the action initially. This is due to being in the easterly (downslope) flow regime of the low pressure center.   The Salt Lake valley and areas to our south will reap most of the benefits in terms of snowfall.  Though, it is possible that mountainous terrain in the Ogden area will benefit from some orographic enhancement once the low begins to move out on Sunday afternoon/evening.  Additionally, this does not look like a big snow-producer for lee-side resorts like PCMR and Deer Valley given the location of the low pressure center and potentially blocking by the windward side of the Wasatch.

In anticipation of the winter weather throughout the Salt Lake Valley, the National Weather Service – Salt Lake City has issued a Winter Weather Advisory for the area. This does not include N. Utah.

Winter weather announcement from the National Weather Service Salt Lake City www.weather.gov/slc/
Winter weather announcement from the National Weather Service Salt Lake City www.weather.gov/slc/

This cold, moist storm system will bring temperatures down to nearly 10 degrees below normal in Salt Lake City, as well as produce widespread precipitation across the SL Valley and areas to our south.   As the low progresses East, it will be situated between two high pressure systems, producing converging flow at the surface.  This convergence zone will move east over the Great Sale Lake and could produce some lake-enhanced snowfall in the overnight hours.  This lake enhancement is a wildcard not only for potential snow totals, but the location of the enhanced snowfall.  This will largely be driven by prevailing wind direction. If the wind has a more westerly component (WNW) and lake enhancement does occur, it could mean more snowfall for areas to the north of Salt Lake City like Bountiful and Ogden. If the wind is strong from the northwest, this would mean more snow for the SLC-Cottonwoods region.

18z GFS 10-m wind speed and mean sea level pressure via models.weatherbell.com
18z GFS 10-m wind speed and mean sea level pressure via models.weatherbell.com

Precipitation is expected to begin this evening in Southern Utah, then begin to fill in to the north and persist through tomorrow mid-day.  Orographic effects will prolong the precipitation in areas favored by northwest flow as the low moves out tomorrow afternoon.  The High-Resolution Rapid Refresh model suggests snow showers beginning briefly in the valley late this evening, then becoming more widespread and persistent in the overnight hours. The latest model run with simulated radar reflectivity is shown below:

HRRR simulated radar reflectivity models.weatherbell.com
HRRR simulated radar reflectivity models.weatherbell.com

Snow Totals: 
Several atmospheric processes must be taken into account when considering the snow total forecasts for this storm system.  The speed of trough movement, potential lake enhancement, and strength of the northwest flow regime will all have a hand in how much snow will fall across Salt Lake valley and central Wasatch. Given the current guidance, here’s what looks most likely:
Salt Lake Valley: 2-4″
Big/Little Cottonwoods Resorts: 10-16″
Sundance: 6-12″
N. Utah (Snowbasin, PowMow): 6-12″
Park City area: 4-8″

Conditions tomorrow:

In addition to snow showers lingering throughout the day, crest level (700 mb) temperatures could be as low as -17 Celsius (0 degrees Fahrenheit) with winds gusting to 40-45 mph tomorrow afternoon.  If you plan on going out to ski, dress accordingly as wind chill values will be much lower than these forecasted values.

18 Z GFS temperature and wind speed/direction forecasts at Mt. Baldy via weather.utah.edu
18 Z GFS temperature and wind speed/direction forecasts at Mt. Baldy via weather.utah.edu

Wednesday and beyond:
Wednesday into Thursday, a weak disturbance crosses the region, which could lead to a few extra inches of snow in the mountains. No major accumulations are expected from this trough. After Thursday, ridging appears to build in, bringing quiescent weather and some potentially awesome blue bird days next weekend as the ski season starts to ramp up. The 500 mb anomaly forecast is shown below, valid next Saturday afternoon. Yellow-orange colors indicate a “positive” anomaly, meaning a high pressure system.

GFS 500 mb anomaly map valid next Saturday
GFS 500 mb anomaly map valid next Saturday

 

For now, enjoy this awesome early-season skiing and a powder day with free refills tomorrow!

-Taylor

Active (Snowy) Weather Continues

TLDR: Snow continuing in waves with an additional 8-12″ of snow for the mountains from Saturday through Monday. A Winter Weather Advisory is in effect for the Wasatch and Uinta Mountains through 4 am MST Saturday morning with accumulations of 3-8″ tonight.


WHAT’S HAPPENING NOW

Let it snow! It’s been snowing in waves around northern Utah mountains since Wednesday.  So far, Alta has gotten 15″ of snow and Snowbasin a whopping 21″. At least 10-14″ of snow has been reported across resorts statewide today. Below is a webcam of Alta’s sugarloaf peak at 4:35 MST today. Looks like it’s coming down pretty hard! In addition, the National Weather Service office in Salt Lake City has issued a Winter Weather Advisory for additional snow amounts of 3-8″ is in effect until 4 am MST Saturday morning for the Wasatch and Uinta Mountains.

Alta Web Cam
Webcam of Alta’s Sugar loaf peak at 4:35pm MST. Courtesy: https://www.onthesnow.com/utah/alta-ski-area/

Below are snow totals as of 10 am MST this morning for local mountain locations as reported by the National Weather Service:

Screen Shot 2018-11-30 at 1.49.58 PMScreen Shot 2018-11-30 at 1.45.19 PM

Total snow and precipitation reported by the National Weather Service as of 10 am MST this morning.
Courtesy weather.gov

THE WEEKEND

Snow showers should continue off and on throughout the day today as a trough overhead progresses into the Rocky Mountains. Expect an additional 3-8″ of fairly powdery snow through early morning Saturday, tapering off by 4 am MST. Another system associated with the  Pacific jet moves in Saturday afternoon, with maximum height falls occurring Saturday evening and Sunday morning. Even though heights should rise gradually Sunday evening into Monday, there likely will be enough unstable, cyclonic flow to create instability showers, especially in higher terrain.  This means we should have more accumulating snowfall in the mountain resorts from Saturday through Monday afternoon.  Additional accumulations look to be in the 8-12″ range during this time for most Utah mountain resorts. Below is the 12Z ECMWF forecast for total precipitation from 12Z (5am) this morning through 18z (11am) 4 Dec (Monday). The Euro predicts an additional 0.8-1″ of precipitation outside of what has already fallen today.

12Z ECMWF total precipitation from 12Z 30 Nov (Friday morning) through 18Z 4 Dec (Monday morning). An additional 0.8-1" of precipitation (outside of what we received already today) is forecast for the mountain areas.
12Z ECMWF total precipitation from 12Z 30 Nov (Friday morning) through 18Z 4 Dec (Monday morning). An additional 0.8-1″ of precipitation (outside of what we received already today) is forecast for the mountain areas. Courtesy: models.weatherbell.com

NEXT WEEK

Ridging moves in next week Tuesday, but a) will not be nearly as strong as recent high pressure events in that it will be “flat” and more “zonal” and b) looks to be exiting rather soon too. A closed low looks to move onto the coast of California by Wednesday afternoon. Flow looks like it will be “split” between the southern branch of the jet south of the closed low and by flow to the north associated with the northern branch of the polar jet. These two flows will merge over our area during the day Wednesday, and a mid to upper level trough will pass through our region Thursday. With the availability of moisture from the southern branch of the jet, there should be a rather large chance for additional light accumulations of mountain snowfall.

GFS 500 mb vorticity chart valid 00Z 7 Dec (Wednesday evening). Not the closed low along the California coast, and flow splitting around it to the south and to the north (associated with the polar jet).
GFS 500 mb vorticity chart valid 00Z 7 Dec (Wednesday evening). Not the closed low along the California coast, and flow splitting around it to the south and to the north (associated with the polar jet).
700 mb vorticity chart valid 18Z 8 December (Thursday morning). At this time, a weak low to mid level (700-500 mb) trough is pushing through the area. This gives us the potential for some instability and precipitation across the region.
700 mb vorticity chart valid 06Z 9 December (Thursday night). At this time, a weak low to mid level (700-500 mb) trough is pushing through the area. This gives us the potential for some instability and light precipitation across the region Thursday afternoon through Thursday night.

Beyond that, ridging looks to build it quite strongly across the region after Thursday, perhaps staying put until Tuesday of next week. More on that  in future posts. In the meanwhile, temperatures should be at or slightly above normal in the mountains next week, making for absolutely perfect skiing conditions!

Enjoy the snow this weekend (I know I will) and stay tuned for more info regarding next week’s potential system.

-Pete