I am starting to get excited about the pattern change and massive storm cycle that is expected to accompany it. The models are showing some jaw-dropping numbers that may rival one of the cycles from last year's miracle May. Since the heavier phase of this cycle is expected next weekend, it's still a bit early to lock anything in, but man, this is looking REALLY good and just what we need heading into mid-June.

It's been a dull and mostly dry run of weather over the last seven to ten days, following the late May storm, and that will continue for a few more days to start the workweek. All eyes are laser-focused on the series of storms, the first of which is expected to move in on Wednesday night.

The ridge that has kept the area dry for the last several days will slowly drift eastward early this week, then stalling east of Argentina in the southwest Atlantic. An unusually deep low-pressure system in the southeast Pacific will track east towards the Chilean coast, causing the overall pattern in this region to become amplified. This, in turn, will lead to strong and slow-moving ridges of high pressure on either side of the low. Finally, this will allow a few low-pressure systems to remain over the Andes, likely through the middle of next week, unleashing several rounds of intense snowfall. Let's take a look.   

First, the upper-level pattern for today, Monday, 6/9, is shown below. You can see the anomalously deep low-pressure system well off the Chilean coast.

Next, we can see the highly amplified downstream ridge as well as a deepening upstream ridge.

Combined, this amplified ridge-trough-ridge pattern will be slow to break down, resulting in an extended period of low pressure and storminess between these ridges over the Andes. You can see this in the GIF below.

This storm cycle is expected to bring in some cold air, with snow levels remaining below base elevations throughout the event. Both the temperature departures from normal and the snow totals are expected to be most significant in the northern zone. Winds don't look particularly heinous during this cycle either, the worst of which are expected in the central zone over the weekend. Snow is possible from Wednesday night of this week through the following Wednesday. Some locations may not see any break during this time. 

Generally, a period of heavy snow is expected Wednesday night through Friday morning, followed by lighter snow on Friday and Saturday. Lighter is a relative term here, as snow should still be stacking during this time. The main event is expected to last from Saturday night through Monday evening, with potentially very intense snowfall, followed by light to moderate snow that will linger through Wednesday. I'll get more into the details in Wednesday's post.

As mentioned, some uncertainty remains regarding snow totals; however, the deterministic and ensemble models indicate healthy amounts, with a widespread 1 to 2 meters across much of the Andes. It is a good sign to see such significant snow totals across the deterministic and ensemble models at this range, but I will fine-tune the forecast in the next post. 

We should dry out, at least for a few days, toward the end of next week. There are some indications of another storm, taking a more northerly track, for the following weekend, but it's a bit too early to get excited. 

My next post will be on Wednesday. 

Thanks for reading the South America Daily Snow!

Luke Stone
Forecaster, OpenSnow

NEW: Forecast Range Graphs

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The graphs give you a behind-the-scenes look at the forecast and make it easier to see if the forecast models are in tight agreement or if there is a wide range of potential outcomes over the next 10 days.

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