Last Call for Powder: The End of a Great Storm Cycle

Posted Friday, January 7th, 2022 by Clinton Alden

TL;DR: 

One last chance for snowfall this weekend before a prolonged period of high pressure builds in Utah. A series of ridges progress through the West over the next week leading to dry weather.

Current Conditions:

Mountain Temperatures and Winds as of 11 am MST 1/7/21. Source

Current temperatures are in the 25 to 45-degree range depending on aspect and topography, with those cooler locations looking to warm up to about 35 degrees as the day progresses. Be on the lookout today for gusty winds that we are currently seeing on the ridgetops up to 30 mph sustained. Additionally, some locations in the mid elevations on the Wasatch Back did not refreeze overnight due to a temperature inversion in the Snyderville Basin. Snow might be on the slushier side in these areas on sunny slopes today.

Short Term Forecast: 

A low amplitude ridge of high pressure is currently centered over the Intermountain West but will quickly move out to the east as a weak trough of low pressure is ushered in. This trough will provide just enough moisture and dynamics to provide us will a little refresh of our base Saturday Morning. Snow to Liquid ratios will be much higher with this storm than the Sierra Cement dense snow the Wasatch saw earlier this week. Snowfall rates should be light and densities in the 7-10 percent range, with snow getting less dense as the storm progresses.

Long Term Forecast:

The main story of the long-term forecast is going to be a series of ridges that progress through the west and an extended dry period. What is causing this? Let’s take a look.

500mb Geopotential Heights and Anomalies for the CONUS valid 5 pm MST Jan 10, 2021. Source

In this ensemble, we can see the 500mb heights for Monday evening. Where we see the black lines bent in an upside-down U-shape represents a ridge of high pressure and the U-shaped wave, such as the pattern of the coast of Southern California, is a trough of low pressure. Where we see a high-pressure north of a trough, such as over the West Coast, is a type of blocking pattern known as a Rex Block that temporarily prevents the pattern from progressing downstream to the east. This block is weak in this case and lasts through Wednesday.

CFS Climate Model with 500mb heights and anomalies for Jan 13 – Jan 20, 2021, over the Northern Hemisphere. Source

As the Rex Block breaks down, a very strong ridge builds over the West Coast. This is a climate model that averages the 500mb heights for the January 13 through January 20 period. The area shaded in red and purple represents anomalously high 500mb heights in a ridge that will block any unsettled weather from reaching Utah through next week. While this is not necessarily the greatest news from a powder perspective, the good news is there is an excellent base of snow in the Wasatch with most major terrain areas open now, barring avalanche control, including Mineral Basin at Snowbird, Honeycomb Canyon at Solitude, and 9990’ lift at Canyons.

State of the Snowpack:

Percent of Median of Snow Water Equivalent for Northern Utah as of Jan 7, 2021. Source

Snowpack throughout Utah is running at or above average for this date, especially in the Southern half of the state. Looks like this last few weeks have made a serious dent in pulling the state out from the long-term drought conditions for the last few years. As mentioned previously, Central Wasatch resorts have a healthy base ranging from 46″ at Park City to 95″ at Alta.

Snow Forecast through Saturday Evening:

Look for generally 3-6” inches of snow for the Central Wasatch upper elevations through the forecast period. Snowfall will be closer to 1-3” for the mid and lower elevation sites along the Wasatch Back at Park City and Deer Valley.

Have a great weekend!

-Clinton Alden

Leave a Reply

Your email address will not be published. Required fields are marked *