High Impact Snow Event for Salt Lake City on Monday

Friday’s storm brought significant snowfall totals to the Wasatch Mountains along with excellent skiing conditions, but impacts across Salt Lake City and the I-15 corridor were much less due to rain falling for much of the event.  However, another potent storm system is approaching from the west with heavier snow amounts expected for Salt Lake City.

The image below is the latest model analyzed upper level pattern from the GFS Model for 5pm Sunday, showing this fast-moving system pushing into Northern California (image source: tropicaltidbits.com).

 

Temperatures are mild again today with temperatures well into the 40s across the urban corridor, but this storm will be moving across Utah from the northwest with a cold front arriving at the leading edge.  Precipitation will be filling in across Northern Utah early Monday morning.  The next image shows the HRRR-model projected precipitation type around 4am tomorrow (image source: weathermodels.com).  Temperatures should be warm enough for precipitation to start as rain or a rain-snow mix across the lower elevations.

 

 

However, thanks to the colder air arriving with the leading edge of this system, we should see a relatively quick change-over to snow across the I-15 corridor as temperatures fall to near freezing.  The next image shows the same model’s projected precipitation type by 7am, which is all-snow across the area (image source: weathermodels.com).

 

 

This will be a relatively short-duration but high-intensity system with most of the snow expected to fall from roughly 7am Monday until sunset for Salt Lake City, with perhaps some lingering light snow showers into the evening.  The onset of snowfall by 6-7am along with the potential for 1″/hour snowfall rates will impact the morning commute Monday as this system comes in strong and fast, with slushy pavement accumulations likely for the urban corridor.  

During the middle part of the day Monday, there may be some melt occurring on the roadways across portions of the metro area since temperatures will be near or just below freezing, but if heavy snowfall rates persist then melting may be minimal.  Across the higher elevation benches, pavement impacts will certainly be more significant.

Snowfall amounts across the I-15 corridor from Provo to Salt Lake City to Brigham City will likely be in the 4-8″ range, with higher amounts possible across the higher elevation benches.  The evening commute will be impacted as well, with the potential for rapid icing on roadways (where melt has occurred) as temperatures begin to drop into the 20s by around or shortly after sunset.

For the Wasatch Mountains, snowfall totals for the town of Park City will likely be in the 6-12″ range with 1-2 feet of snow likely for the ski areas.  This will be another high impact event for the mountains with significant travel difficulties expected.  Strong northwest winds will result in areas of blowing and drifting snow as well.

Snowfall should eventually taper off Monday evening for Salt Lake with overnight lows falling to around 20, but snow will linger well into the overnight period for the Wasatch Mountains.  Schools will fortunately be on a break Monday for Martin Luther King Day, but should be prepared for slick roads Tuesday morning.

Winter storm to impact Chicago area tonight

An impressive storm system moving across the Central U.S. will impact Northern Illinois and the Chicago metro area tonight, bringing significant snowfall to the region.  The center of the low pressure system will be tracking well south of the area, but strong south/southeasterly flow will transport abundant moisture northward to bring snow to the region.

The onset of snow looks to begin across the Chicago area right around rush hour, which could impact the evening commute as snow should easily accumulate on pavement through this event.  The image below shows the HRRR-model simulated radar reflectivity, which projects snow to be reaching Chicago around 6pm local time (image source: tropicaltidbits.com).

 

 

A steady snowfall can be expected for Chicago metro from early this evening through Saturday morning, with many areas likely to pick up 6″ or more of snow.  In general, the heaviest amounts are expected north of I-88, but banded snowfall could result in varying amounts.

Road conditions will quickly deteriorate tonight through Saturday morning, and strong winds from the east/northeast at 15-25mph with gusts to 35mph will result in areas of blowing and drifting snow.  The heaviest snow should come to an end during the morning hours Saturday with additional lingering light snow showers.

However, the potential for lake effect snow will arrive from late Saturday through early Sunday, with additional snow accumulations possible during the overnight period Saturday night-Sunday morning.  The additional lake effect snow along with breezy north/northeast winds will continue to impact travel conditions through Sunday. 

Snowfall should eventually come to an end by Sunday afternoon or early evening, but cold air arriving Sunday night will keep high temperatures in the teens on Monday.

Heavy snow tonight west of the Divide in Colorado

A Pacific storm system is moving into Western Colorado tonight with heavy snowfall amounts expected across much of the higher terrain of Colorado west of the Continental Divide.  This storm system has already produced several feet of snow across the Sierra Nevada in California, as well as heavy snow in Utah.  

Colorado’s mountains are now getting in on the action as well, with southwest flow favoring the San Juan and Elk Ranges south of I-70 initially.  The image below shows the most relative humidity analysis at the 7,000-millibar relative, which corresponds to roughly 10,000′ of elevation and is a good measure of moisture for the mountain areas of Colorado.

 

 

Later tonight, a gradual shift in the upper level flow from southwest to west, and eventually northwest, will allow the mountain areas along and north of I-70 to pick up heavy snowfall amounts as well.  By Friday morning, most of Colorado’s mountain areas west of the Continental Divide will have picked up impressive snowfall amounts, with double digit totals likely for many ski areas.  Road conditions will quickly deteriorate tonight through Friday morning throughout the Colorado’s high country, making for a challenging Friday morning commute.

East of the Continental Divide, this storm will mostly be a miss for the Front Range cities due to a lack of upslope flow.  However, a cold front will arrive Friday morning as the low pressure system swings across the Continental Divide, and banded snow showers are expected to develop across the I-25 corridor during the daytime hours.

Winds from the north/northwest will be unfavorable for Denver snow, with most areas east of the mountains expected to receive snowfall amounts of less than an inch, except perhaps under isolated heavier bands or across the Palmer Divide.  Temperatures near freezing as well as the timing during the daytime hours should also limit road impacts across the Denver area and I-25 corridor.

Looking farther out, the next system is slated to reach Colorado on Monday, and at this time there appears to be a chance for Denver to see a more meaningful snowfall event Monday night or Tuesday.

Heavy snow for the Wasatch with rain changing to snow in Salt Lake City early Friday

A powerful Pacific storm system is moving into Utah from the west today after dumping heavy amounts of snow in the California’s Sierra Nevada Range (measured in feet) over the past couple of days.  The image below shows this morning’s water vapor satellite imagery, which clearly shows the deep moisture streaming into Utah from the southwest (image source: NOAA). 

 

 

Along with the deep moisture, warmer air from the southwest has also advanced into Utah ahead of this system.  As a result, we will see mostly rain falling in Salt Lake City and the I-15 corridor throughout the day Thursday with temperatures in the 40s.  Snow levels could rise to 6,000′ or higher this afternoon.

Above the rain/snow line, heavy snow will fall in the Wasatch today and tonight, much to the delight of skiers who will enjoy some deep powder conditions on Friday.  For the Park City area, temperatures may be warm enough this afternoon to prevent significant road impacts, though slushy accumulations are certainly possible.  The below image shows HRRR-model projected temperatures this afternoon across Utah (image source: weathermodels.com). 

 

 

The biggest travel impacts with this storm will occur tonight through Friday morning as a cold front arrives.  Road conditions will quickly deteriorate across the Park City area as well as Big and Little Cottonwood Canyons as heavy snow continues to fall as colder air filters into the region.  

The heaviest precipitation will occur through roughly midnight tonight, but additional moisture will linger into Friday as well.  Late tonight, we should see a transition from rain to snow across the Salt Lake City area and the I-5 corridor, with snow expected to impact the Friday morning commute.

Temperatures are projected to be close to freezing Friday morning in downtown Salt Lake City, and the higher snowfall amounts along with more significant pavement impacts will occur across the higher elevation benches across the metro area.  

For snowfall amounts, projections are generally in the 1-3″ range for central Salt Lake City along the I-15 corridor, with higher amounts across the higher elevation benches.  For the Wasatch, the town of Park City could see 7-14″, while the higher elevations of the Wasatch ski areas will likely be in the 1-2 foot range with isolated higher amounts possible.  The next image shows the HRRR model’s projected snowfall amounts across the area over the next 24-hours (image source: weathermodels.com).

 

Colorado High Country Snow

A Pacific storm is approaching Colorado’s High Country today bringing winter weather across the Rockies over the next couple of days and will impact travel conditions as well as bring beneficial moisture to the mountains.  With this storm, all mountain areas will be impacted, with higher snow totals along higher elevations and west facing slopes.  Best chances for snow per NWS are as follows:

Expected Snowfall - Official NWS Forecast

A 10% chance of seeing higher amounts:

Maximum Potential Snow Accumulation

Generally snowfall amounts should fall into the 1-3″ range with higher elevations looking more in the 4-8″ with isolated higher amounts possible on west facing slopes up to 12″ possible with this storm.  Here is a look at the percent chance of 4″ or more across the Colorado High Country:

And a percent chance of greater than 8″:

Snow has just started creeping into the western portion of the state with snow increasing today and falling through the day tomorrow.  Expect some travel delays, specifically along higher elevations including mountain passes.  If you have the chance to get up to the High Country to ski, it should be a good time to ride some fresh powder this week without having the weekend rush of people!  

Sublimation?

Most people know what evaporation is, when a liquid transfers into a gas, such as wet roads after a rain storm when the sun shines and you can see steam rising from the surface.  When temperatures are cold, generally below freezing, snow will also behave in the same matter as liquid water, but this process is referred to as sublimation and not evaporation.  Sublimation is the transfer of a solid into a gas, in this case ice turning into steam directly before melting.  Unfortunately sublimation does not provide the ground with any beneficial moisture since all the moisture is released back into the atmosphere.  A good time to catch this phenomenon visually is in the early morning as the sun rises providing just enough heat, while surface temperatures are well below freezing.  Here is an image I took Sunday morning when temperatures were hovering around 20 degrees at the surface and the sunlight was just hitting some frost on the fence allowing for sublimation.  In order to confirm it was sublimation and not evaporation was that the fence never became wet or even looked like there was any type of moisture on it once all the frost sublimated into the air.

Another process that can create sublimation is wind.  Cold, windy days with below freezing temperatures where snow does not melt by warmth, but visually dissipates is usually caused by sublimation as well.  The tell tale sign this has occurred will be that the top layer of snow is smooth and crunchy with dry, crumbling snow below and the ground is still hard and dry beneath.  This indicates that the moisture from the snow has sublimated into the atmosphere and did not melt into the ground below.  Sublimation is a process that is not beneficial for providing drought relief, although, fortunately it does not occur that often since Colorado needs all the moisture it can get!    

 

Variable Snow Totals Along the Front Range

Friday’s winter storm dropped a healthy amount of liquid precipitation along the Front Range, but snow totals proved highly variable due to marginal storm temperatures. Much of the snowfall at the lowest elevations did not stick to road surfaces, and also compacted significantly due to the high moisture content. Rain also mixed with snow over the northern and central metro area throughout the day on Friday, further diminishing potential impacts on road surfaces. Below, you’ll find a collection of local storm reports showing a high degree of variability.

Shaffers Crossing (3N) 18”
Tiny Town (3S) 16.5”
Aspen Park 13.4”
Perry Park 12”
Golden (3SW) 10.9”
Elizabeth (2E) 10”
Highlands Ranch 8.3”
Castle Pines (3S) 7.1”
Boulder (3NW) 4.5”
Aurora (3SSE) 4”
Englewood 2.8”
Lakewood 2.7”
Denver (2E) 2.2”
DIA 1.3”
Fort Collins (3SW) 0.2”

The storm generally favored areas west of Interstate 25 and south of Interstate 70. The Foothills of Jefferson County, Douglas County, and areas along the Palmer Divide saw the most precipitation, where more than 1.00″ of liquid was observed in some areas. Higher foothills near Conifer topped the scales with 15-18″ of snowfall observed.

Heavy snowfall west of Conifer 01/12/19.

Light snow showers and flurries remain possible on Saturday, but little accumulation is expected. By early afternoon, there’s a good chance for breaking skies to help melt the recent snowfall. Temperatures will slowly rebound this week as high pressure steadily builds into the Rocky Mountains. Eyes then turn towards our next period of unsettled weather, perhaps arriving on Friday as a trough of low pressure takes aim at Colorado.

The Next Round of High Country Snow

Snowfall for the Colorado High Country started out strong this season with many ski resorts opening early for the first time in a decade.  Unfortunately as we’ve moved into 2019 the snow has been both, less frequent and very few days with high accumulations.  This has lead to snow pack totals to creep closer to 100% in the northwest, with a statewide total of only 95% as seen below:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Currently a storm is headed towards Colorado from the Pacific which will bring some beneficial snowfall to the High Country.  This snow should start impacting the region Thursday afternoon and could last into early Saturday morning before pushing eastward and out of Colorado.  Best chances for snow with this storm will be in the central Rockies along the Continental Divide which is generally the case with west to east storms.  Here are the percent probabilities provided by NWS for an inch or above snowfall over the next two days:

It appears there will a good chance for the entire state to see at least some snowfall, but as the accumulations go up, the probabilities drop significantly as seen below on areas expecting more than 4″:

This indicates that there will be a good chance to see snow over the next couple of days, although amounts will most likely be minimal.  At this time there is a lot of model uncertainty as is usually the case with west/northwest to east/southeast storms.  Considering the pattern we have been in, the snowfall amounts indicated below seem more likely:

Expected Snowfall - Official NWS Forecast

Although I would expect totals in the southern, central Rockies and along the Continental Divide, especially western facing slopes receiving amounts closer to these:

The NWS only has a 10% chance for amounts in the 6-12″ range for the Colorado High Country, but I would certainly give a 50% chance to at least see half of those amounts across portions of the Continental Divide, the San Juans and Sangre de Christo ranges! 

 

 

 

 

 

New Years Even Snow Across The Denver Metro

A blustery storm system moved through Colorado New Years Eve bringing snow across the region along with very cold temperatures.  Unfortunately temperatures were too cold to enable good dendrite growth leading to most falling snow to be a very light, powdery snow.  Strong winds from the north throughout the day caused blowing snow and poor visibility with small drifting in some areas.  Preliminary snow totals this morning around 8:30 AM via local storm reports are as follows:

Snow favored the western and south side of the Denver Metro Area with totals ranging from 2-4″.  Denver, north and east had less accumulations between 1-1.5″ reported with DIA’s official total coming in at only 0.5″ from New Years Eve’s storm.  Hopefully this will lead to a more active winter as Denver has seen little to no snow so far this season.    

Broncos Game Day Forecast

The Denver Broncos will close out their season today against the Los Angeles Chargers at home and the weather looks to be very pleasant for December standards.  Below is the game day forecast:

Conditions will be pleasant today in Denver for the last game of the season.  Temperatures will warm into the lower 50s under mostly sunny skies through early afternoon then skies become partly cloudy later afternoon.  Highs will be reached between 1-2pm with the majority of the game experiencing temperatures in the 40s.  Winds will be light, mainly varying from SW to NW at less than 10mph.  A storm system will move into the Denver Metro area overnight with widespread snow through the day on Monday.  GO BRONCOS!!!    

 

                                                Game Day Forecast

Time Temp (F) RH % Wind

(mph)

Conditions Precipitation
12:00 PM
50
24%
SW 4-8
MSunny
DRY
1:00 PM
51
24%
SW/W 4-8
MSunny
DRY
2:00 PM
50
25%
W/NW 4-8
MSunny
DRY
3:00 PM
48
29%
W/NW 4-8
MSunny/PCldy
DRY
4:00 PM
46
31%
NW 4-8
PCldy
DRY
5:00 PM
42
36%
N/NW 4-8
PCldy
DRY
6:00 PM
40
39%
N/NW 3-6
PCldy/MCldy DRY