We are on the door step of what will likely be the biggest storm of the season. The heaviest snow will fall in the northern zone, with lesser but still substantial snow for the central resorts. The snow will continue for nearly six days before winding down. After a short break, more snow is possible the following weekend.
Short Term Forecast
Today, Friday, is the day! The storm we have been waiting for arrives late tonight. After a small and fast moving upper level system moves through the region Friday night, a strong, large, and slow moving upper level area of low pressure will move across South America from Saturday through Thursday. See how the upper level pattern pattern unfolds below.
As I mentioned in the last post, a long duration atmospheric river will be providing abundant moisture during this time. While the atmospheric river won’t remain stationary over one area, it will spend the most time delivering ample moisture to the northern zone.
In the GIF below, you can see long, narrow plume of moisture fluctuating along the coast. This fire hose of upper level moisture focuses on the northern zone, shifts south to the central zone, and then returns to the north once again.
This will focus the heaviest precipitation and greatest snowfall amounts on the northern resorts.
This long duration snowfall will feature strong winds at times as well. Winds will ramp up Saturday morning, and remain strong through Wednesday. Check out the 3000 m winds below throughout the storm.
Winds won’t be as much of an issue for the lower elevation central resorts, but in the north, above 3000 m, they will be strong, gusting over 80 km/hr.
Forecast for Friday 8/18 - Thursday 8/24
Some light snow is possible during the day today, Friday, but the brunt of the storm arrives tonight. Initially, a warm front will move through the region, increasing snow levels. By Saturday afternoon, temperatures will start to cool off just a bit, but will again increase on Sunday. Snow levels could creep high enough for rain at some of the lower elevation central resorts during this time. On Sunday night however, a strong cold front will push north across the Andes, and the remainder of the storm will be cold.
For the northern resorts, like Portillo, Las Lenas, and Valle Nevado, it will be absolutely dumping nearly non stop from late Friday night through Wednesday of next week. The models are still showing well over 500 mm, or 50 cms, or nearly 20" of precipitation during this period.
This should equate to 1.5 to 3 meters of snow in the northern zone! For every twelve hour period during this time, expect between 20 - 50 cms. So, there should be 20 - 50 cms fresh each morning, with another 20 - 50 cms during the day as well.
Obviously, this amount of snow will impact roads and resorts, with likely closures of both at times. Resorts could remain closed for multiple days, as avalanche danger will likely reach extreme levels.
As you go a little farther south, for the resorts in the northern part of the central zone, the totals won't be as impressive, especially with higher snow levels during the first part of the storm. These resorts, like Nevados de Chillan, Corralco, and Los Penitentes, will still see one of the, if not the biggest storm of the season, with 1 - 2 m of snow. The lower elevation resorts in this region, like Pucon, Las Araucarias, Antillanca, Cerro Catedral, Antuco, Cerro Bayo, Chapelco, and Volcan Osorno will see quite a bit less, between 50 - 100 cms. That is still a massive amount of snow. Meanwhile, resorts in the southern region can expect 10 - 20 cms.
This is truly an impressive and exceptional storm, and it will be fascinating to see what terrain the resorts can open during this time. Check out the snow forecast from the American model below.
Outlook for Friday 8/25 - Tuesday 8/29
So what is going to happen once this storm clears? The models have been back and forth between showing a break between storms and more active weather arriving over the weekend. Some light snow may linger through the day on Friday, but the latest data suggests the next storm may arrive on Sunday or Monday. So it looks like the break will be short, but perhaps long enough to get some additional terrain open before the next round of snow.
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