Active Weather Returns

One more day of mild, bluebird conditions up in the mountains and smog in the valley before the next storm system pushes into the region. Between Thursday and Monday 3 systems will cross through the region as shown in the animation below from the GFS.

Animation from GFS
Animation from GFS

Storm #1 will skirt through southern Utah Thursday morning through Thursday night.  It looks like northern Utah will miss the brunt of this storm. Totals should range from 6-12″ in northern and central Utah to 12-20″ in southern Utah down by Brian Head and Eagle Point.

Storm #2 will enter the region Saturday morning and it too appears to track through southern Utah and northern AZ/NM.

Storm #3 has the potential to be much stronger than the two before it.  It’ll impact Utah on Monday.  Keep an eye on this one – the NAEFS shows the potential for a significant system.

1/17/16 12Z NAEFS forecast for Upper Cottonwoods
1/17/16 12Z NAEFS forecast for Upper Cottonwoods

Previewing the Week Ahead

Valley cold air pools (“inversion”) will continue through Thursday morning before a cold front clears things out Thursday night into Friday morning.  Across the valleys, air pollution has only managed to reach the moderate category so far, with the exception of Cache Valley, where air quality has reached the unhealthy for sensitivity groups category.  A deep cold air pool is currently in place with the top of the inversion around 7500 feet.  Typically during inversion events, the top of the inversion is between 5500 – 6000 feet.  With the top near 7500 feet in this event, pollution is able to spread out through a deeper layer of air, keeping PM2.5 concentrations on the lower side.

Salt Lake County PM2.5 trend from Jan. 12 to Jan 16th. Courtesy: http://air.utah.gov/trendcharts.php?id=slc

High pressure will remain in place across Utah through Thursday morning.  700 mb temperatures will warm from around -5 C tonight to -1 C by Tuesday afternoon, yielding warmer temperatures (30-35 F) across ski resorts Tuesday and Wednesday.

A series of storms will move through Utah Thursday afternoon through Monday.  The first storm will arrive Thursday afternoon, with best dynamics across central and southern Utah.  Snow showers will develop Thursday afternoon before tapering off Friday morning.  Another shortwave trough will arrive Friday afternoon.  Once again this storm will mainly impact central and southern Utah will light accumulations across northern Utah.  A stronger storm will impact northern Utah Monday, but this system is a week out, with details easily changing by then.

NAEFSPL_CLN2017011612F168 (1)

NAEFS Precipitation and Snowfall Forecast for Alta. Courtesy: weather.utah.edu

Bottom Line

  • Tuesday will be another blue bird day with slightly warmer temperatures.
  • Wednesday will be another great day with high clouds moving in by the afternoon.
  • Active weather returns to Utah Thursday through the weekend with a series of storms dropping new snowfall.  The first two storms will be on the weaker side, but could drop anywhere from 6-16″ across the Wasatch.

Hazy days

A quiet weather weekend gave way to gorgeous conditions at the resorts.  You were treated to blue bird mountain conditions if you climbed up high enough to escape the inversion currently blanketing the city.
Our current break from the storm cycle is disrupting the air quality in the valley, causing PM2.5 particulates to build up.  This results in that foggy haze that you woke up to this morning. Unfortunately, this inversion episode will likely stick around until Wednesday.

The active pattern appears to return Thursday with a shortwave trough making its way into northern Utah.. While this storm appears to be colder than the previous few, it still looks like we will see only rain in the valley due to elevated snow levels. This active pattern should continue through the weekend.

ECMWF 500 mb heights. Valid 18 Z Thursday. Image: Weatherbell
ECMWF 500 mb heights. Valid 18 Z Thursday. Image: Weatherbell

Thanks to the active pattern we have been blessed with since the beginning of the year, snowpack SWE levels are well above normal.  Lets hope this coming week can add to it!

Current SNOTEL Snow Water Equivalent percentage of normal.
Current SNOTEL Snow Water Equivalent percentage of normal.

Enjoy the Sunshine

Not a whole lot to talk about tonight, so I’ll keep it brief. A tremendous storm cycle has left the skiing across the state of Utah in spectacular shape. The backcountry will finally have a chance to (slowly) stabilize this weekend as winds remain light and no new snowfall is expected. For those of you about to enjoy a three day weekend, it should be a beautiful one, with ample sunshine Saturday, Sunday, and Monday at the resorts.

Down in the Salt Lake Valley we’re watching the development of an inversion leading to decreased air quality this weekend, with the effects already noticeable today. Carpool to the resorts if you can, and help limit our contribution to the pollution during this period.

Vertical profile for SLC from the NAM12. Note the development of a significant inversion, where temperatures (rightmost red line) warm with height in the lower levels.
Vertical profile for SLC from the NAM12. Note the development of a significant inversion, where temperatures (rightmost red line) warm with height in the lower levels.

 

500 mb heights fall significantly by late next week, indicating the return to troughing to our west and another stormy period into next weekend. Way too soon to talk much about details but it looks to be a colder storm than the last few that impacted the state. Stay tuned, and enjoy the skiing!

ECMWF ('Euro') Ensemble Meteogram. Ensemble members show strong agreement in a period of significant precipitation beginning midweek, Jan 18-22, then uncertainty out beyond some light precipitation to end the week.
ECMWF (‘Euro’) Ensemble Meteogram. Ensemble members show strong agreement for a period of significant precipitation midweek, Jan 18-22, then large uncertainty beyond a period of light precipitation to end the week.

Finally, a Break

This current storm cycle has finally come to an end.  We didn’t do too bad in Utah, as Alex pointed out, but the true winner was the Sierra Nevada.  Mammoth Mountain is reporting a storm total of 101-154″ with a summit base depth of 245″!!! (I’m skeptical about that measurement)  The snowpack across most of the west is looking very healthy as we head into the heart of the winter.  Most SNOTEL sites are reporting 125-200%+ of their median SWE for today.

Screenshot 2017-01-12 20.08.00
SWE percent of Median for SNOTEL sites from NRCS

The next several days look sunny and dry for the entire region.  Temperatures will be comfortable with highs in the upper 20’s in the mountains each day.

All models agree that active weather returns on Wednesday next week.  It’s early, but it looks like we could be in for another prolonged stormy stretch.  Stay tuned!

Snow Continues in the Wasatch through Friday

Snow just keeps on flying in the Wasatch! Snow totals over the last 48 hours have been impressive with Deer Valley topping the list at 37″!

  • Deer Valley: 37″
  • Brighton & Powder Mow: 32″
  • Beaver Mountain: 29″
  • Park City: 28″
  • Solitude & Snowbasin: 19″
  • Snowbird: 18″
  • Alta: 17″

With all the new snowfall in the Wasatch, the avalanche danger continues to be high in the back country.  The Utah Avalanche Center has issued an avalanche warning for high avalanche danger through 6 am Thursday, Jan 12th.

Capture
Utah Avalanche Center Forecast for Salt Lake region. Courtesy: https://utahavalanchecenter.org/advisory/salt-lake

Scattered snow showers are expected to continue overnight with an additional couple of inches falling in the Wasatch.  By Thursday morning the next system is right on our doorstep.  Snow will develop across southern Utah before moving into the Central and Northern Wasatch by the afternoon.

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HRRR Simulated Radar Reflectivity for tonight through tomorrow afternoon. courtesy: weatherbell.com

Snow will continue across the Wasatch through Friday morning before tapering off during the afternoon.  Low density snow will fall Thursday with several inches of powder expected by Friday morning.  Areas in the northern Wasatch will see lesser amounts of snowfall as the storm will centered in central and southern Utah.  Skies will clear out this weekend with excellent weather expected for skiing.

Snowfall Forecast (Tonight – Friday afternoon)

  • Upper Cottonwoods: 6-12″
  • PCMR & Deer Valley: 5-10″
  • Northern Wasatch Resorts: 3-7″

A Bad Case of the “Powder Flu”

Ah, the dreaded powder flu… An epidemic that seems to be spreading across Northern Utah like wildfire.  If you have this terrible illness, its best to stay out of the office and get some fresh air.  No need to infect your fellow office mates 😉   If you are suffering from said ailment, you probably are enjoying these 24-hour snow totals:

Deer Valley: 19″
Beaver Mountain: 15″
Pow Mow & Brighton: 12″
Snowbird: 11″
PCMR, Alta, Solitude: 10″

Currently, even more snow is falling in the mountains as orographic effects are condensing all the moisture out of this potent airmass.

KMTX Radar Image. NWS SLC
KMTX Base Reflectivity         radar.weather.gov

 

With all the heavy, wet new snow, the Utah Avalanche Center has issued a Backcountry Avalanche Warning through Wednesday at 6 pm.  The current threat level for high elevation Salt Lake area mountains is a 3/5 or “considerable”.  This is expected to be updated to a 4/5 or “high” avalanche danger.

 

Utah Avalanche Center Advisory
Utah Avalanche Center Advisory    utahavalanchecenter.org

 

The next round of precipitation for the Intermountain West will begin in the overnight hours as a trough currently located off the coast of California moves into our area.  This afternoon, moderate, low-level southerly flow will advect warm moist air into the region before the frontal passage associated with the impending trough.  Precipitation will become widespread into the early morning hours on Wednesday due to thermally-driven lift as the trough enters the area.  Persistent mid-level westerlies will aid in transporting plentiful moisture throughout the duration of the event.

Time-Height cross section of potential temperature and relative humidity. Note the frontal passage around 12 Z on Wednesday where the potential temperature contours are vertical and the low-level winds veer to westerly. weather.utah.edu
Time-Height cross section of potential temperature and relative humidity. Note the frontal passage around 12 Z on Wednesday where the isentropes are vertical and the low-level winds veer to west-southwesterly.
weather.utah.edu

This moist unstable air mass should keep the snow cranking through Thursday.  This event as a whole will be a warm one, thus keeping snow levels elevated and limiting the valley to rain.
On Friday, a cut-off low will plunge into the southwestern U.S. from the PNW.  This could allow for the southern Utah resorts to rack up a few last minute additions to their growing snowpack.

For Northern Utah, I would expect to see a storm total of 24-36″ through Thursday, with locally higher amounts, especially in the Cottonwoods.  For Southern Utah, 10-20″ at high elevations through Saturday as the remnants of the cut-off low moves out.

So Much More to Come

Yet another huge wave of moisture is about to move through northern Utah. As Mike discussed earlier (and I’m sure you saw if you were outside late this afternoon) a cold front moved through bringing a brief bout of snow to the area. It’s now 11 PM MST, the showers are winding down in the mountains, and Alta is reporting 3″ from it. Winds during and before the event were strong with most mountaintops reporting gusts over 60 mph and Mount Ogden reaching 110 mph.

Basically this storm made for a pretty show but didn’t leave much new snow on the mountains to counteract the prefrontal melting. However, the clearing that’s going on overnight and into the morning is providing a good window for avalanche control in preparation for what’s coming (nearly the entire north side of LCC is closed tonight).

During the day Tuesday, yet another strong atmospheric river event will impact northern Utah. Like the others we’ve seen, snow levels will be on the high side and most of the precipitation will fall in the mountains. The snow is expected to fall all the way through the middle of the day Thursday which provides a very long window to accumulate snow. Ratios for this event are hard to pin down as that is going to depend so much on local wind speeds, temperatures, and precipitation rates which will vary wildly during the event.

Three inches of water are expected as a maximum in the central Wasatch with closer to two inches in the lower elevations. The lower elevations will see warmer temperatures, so I’m predicting 18-26 inches for Park City area and the Northern Wasatch. For the Cottonwoods I’m saying 30-42 inches between now and Thursday evening. With the radar forecast to look somewhat like this the next two days, it’s going to be an exciting time.

hrrr_ref_slc_18

Quick Storm Update

2:00 PM Update: Nudged snow totals down due to present weather underperforming models. Could still see some strong and organized snow squalls.

HRRR 10:1 Snowfall Accumulation Through Tues 6 AM
HRRR 10:1 Snowfall Accumulation Through Tues 6 AM

Previous:

Snowfall overnight became light and sparse across the region, though we’re finally seeing snow redeveloping all along the Wasatch this morning, and with great intensity. Temperatures at Alta guard were in the mid to low 30s last night, and have finally fallen solidly below freezing as of 6:00AM. Snow levels will hover around 8000′ this morning before crashing down towards the valley floors late afternoon/early evening. However, worth nothing that 9000’/11000′ ridgeline winds will hover around 35/50 mph with gusts up to 55/85 mph, making for an interesting ski day out there. A slight chance of lightning and thunder this afternoon with the passage of the front exists.

Current Radar Loop
Current Radar Loop 8:45AM Mon 1/9

Once the front comes through and snow lines descend, density of the snowfall will begin to decrease, with snow falling this afternoon and overnight being of better quality for our skiing. Expect some snow to accumulate in the valleys by Tuesday morning as well.

NAM12 Meteograms, Note descending snow levels with decreasing temperatures at Baldy Summit elevation.
NAM12 Meteograms, Note descending snow levels with decreasing temperatures at Baldy Summit elevation.

I’d say we could expect around 5-10″ in the Park City area and lower Cottonwoods by tomorrow morning, 6-12″ in the Northern Wasatch/Ogden area, and 6-12″ in the upper elevations and favored areas of the Cottonwoods.

GFS Precipitable Water Anomaly, with another maxima forecast into Wednesday
GFS Precipitable Water Anomaly, with another maxima forecast into Wednesday

Not much of a break in snowfall between now and Thursday when the column finally dries out. We see another maxima in the column perceptible water anomaly mid-week. Alex will have more on this for you this afternoon/evening.

Mike

Atmospheric River to arrive Saturday afternoon into Sunday

Brrr… it sure has been cold across Utah the past few days. Peter Sinks bottomed out at -53 F, Logan reached -28 F, and Salt Lake City dropped down to -5 F last night.  Tonight will be the last night of very cold temperatures as warmer air returns to Utah Saturday evening into Sunday afternoon.

utah_temps
Friday, Dec. 6th low temperatures across Northern Utah.

Another atmospheric river event will impact Utah Saturday afternoon through Wednesday morning.  700 mb temperatures will warm from -12 C to -1/2 C by Sunday afternoon as the atmospheric river moves into Utah. This will a strong atmospheric river event with water vapor transport values in the 99 to 99.5 percentile for this time of the year in northern Utah.  Winds are expected to be out of the west to southwest for the duration of the event favoring west-southwest facing slopes. With 700 mb temperatures warming to -1/-2 C by Sunday afternoon, snow levels will be on the rise – reaching 9000-10,000 feet Sunday afternoon into Monday morning, with many ski resort bases seeing rainfall.  Snow levels will lower to around 7000-8000 feet Monday afternoon and eventually will lower near the valley floor Tuesday.

naefs_2017010612_west_pctl_ivt_sfc_60
Sunday afternoon NAEFS Mean Integrated Water Vapor Transport. courtesy: http://ssd.wrh.noaa.gov/satable/

A cold front will slide across Utah Tuesday morning with precipitation winding down overnight.  An active weather pattern will continue across Utah through the end of next week as the pacific jet continues to stream into the Western U.S.

naefspl_cln2017010612f168

NAEFS precipitation and snowfall for Alta. Courtesy: weather.utah.edu

The duration of the atmospheric river event is helping to drive up modeled precipitation amounts across mountain areas.  The NAEFS ensemble is producing anywhere from 4-6″ of water in the Cottonwoods by Wednesday morning, translating to around 40-55″ of snow.  High density snowfall Saturday afternoon through Monday will keep avalanche danger elevated, as wet dense snow falling on top of dry powder tends to create avalanche problems.

Still a bit early to forecast snowfall amounts for the duration of the system, but I expect several feet will fall across the Wasatch through Wednesday, with the highest amounts above 9,000 feet on west-southwest facing slopes.  Lower elevations (6,000 – 9,000 feet) will see lesser amounts as snow levels remain high until Monday afternoon.