A Potential Return to Winter Weather Next Week

We finally have the makings of a weather pattern change in the West, starting early next week. The past few weeks, I have discussed the potential for a retrograding long wave pattern toward the end January into early February. Indeed, it appears this shift will soon be underway. In the world of weather forecasting, nothing is ever simple. Hence, the accurately coined phrase "weather is an imperfect science". While I believe changes are on the way, aspects of the extended outlook are still rather merky. I will get to that in a moment. 

Let's first check up on mountain snowpack as we near the end of a relatively dry month. Good news first. Thanks to blockbuster mountain snowfall in December, snow water equilvalent (SWE) values are still in decent shape. Although storms were lacking much of January, SWE values are still close to normal in most regions, as of January 25th. Southern Utah, and Southern Nevada are well above average. While, Colorado and Wyoming are not faring as well.  

It's best to measure progress using the water year calendar, which runs from October 1st to the end of September the following year. This allows us to visualize the seasonal data. Let's take a closer look, starting with the Alta Resort measurent site. They maintain good records. How has the snowpack progressed since Oct 1st 2021? Here's the data:

The brown line is average snowfall from October 1st to current date. Green is accumulated snowfall. Alta has had 192.9" so far, not far below the average of 218.2". Highest on record is blue, and red is lowest. 1983-1984 had some crazy extreme snow up to this point! What does average yearly snowfall (by month) look like for Alta: 

The bar graph shows the best snow months are Dec-Jan-Feb, with March not far behind, in 4th place. Point being, we still have a couple of the best months for mountain snow to come. What about the valleys? Here's the liquid precipitation and snowfall at the Salt Lake Airport for the water year to date:

Surprisingly, the airport still has above average precipitation, for the water year to date. However, SLC snowfall only stands at 22.1" to date, almost all of which fell in December. A normal year would have 30" of snowfall by this point in the year. 

Let's see if we can do some catch up, alright! Here is the Climate Prediction Center's 6-10 day outlook. For the interior West, near to above average precipitation and colder than average temperatures. They also believe a pattern shift will occur by early February! 

This season has featured some huge monthly flip-flopping extremes in temperatures and precipitation.  It just so happens, the storm-blocking high pressure ridge near the West Coast, will begin a westward shift.  I hope this will open the door to storms arriving from the northwest. Look at the 500 mb trough anomaly for the first week of February:

This particular GFS model develops a long wave trough over the West. Think of the upper height anomalies (deep blues) as a region where storms are likely to be active. Looks interesting! 

I have a word of caution here, listen up! Not all models agree on the strength and location of the big weather influencers come early February.  Uncertainty is quite high!  We could get a short window of active weather, or set up a pattern favorable for a series storms. Hopefully, the latter. 

That said, I am watching one storm of interest, expected to reach Utah early next week. It arrives from a cold trajectory, so I would expect mostly snow in the valleys (except far south). In fact, much of the state could get some decent snow including the mountains-- you're welcome skiers!  It's way too early for further details. Just know there could be appreciable snowfall around Monday-Tuesday next week. 

Below is projected precipitation accumulation through the 10th of February at the SLC Airport. There is minimal skill that far out, so only focus on the trend. Notice the green line (mean of 30 model runs) trends upward around next Monday-Tuesday through the first 10 days of February. A potentially wet/snowy period in Salt Lake City, and possibly much of the state and surrounding region.