The first system that will move through the region from Friday night through Saturday is on the weaker side, and will mainly bring some light snow to the northern zone. Just a few to 10 cm are expected during this time. There is a bit of an easterly component to the winds with this system, which may allow Las Lenas to come in on the higher end of those totals.

Here is a look at the totals from the first storm.

Things begin to get messy on Saturday night, as a closed low forms over central Chile, then begins to retrograde, and ultimately stalls off the coast for potentially several days. Closed lows are detached from the predominant west-to-east upper-level flow. So when the storm is retrograding, it's moving from east to west, in opposition to the main flow.

This often results in a tricky forecast for a variety of reasons. The east-to-west flow can result in unusual wind patterns which make forecasting snow a bit harder. Additionally, closed low-pressure systems often stall when they detach from the flow, allowing a prolonged period of similar weather in some locations.

In this case, the winds are weak and moisture is limited initially, so impacts from Saturday night through Sunday should be limited. However, once the low retrogrades back over the ocean, the clockwise flow will bring better moisture into the region north of the system. Where this moisture combines with easterly flow, there will be a period of moderate to heavy snow.

The position of the low-pressure system when it stalls will be important to who gets the most snow. Right now, it looks like the eastern side of the Andes, between Las Lenas and Cerro Catedral, would have the best chances for solid snow totals. There could be a smaller area within this region that gets a pretty big dump, but it will depend on the location where the low stalls.

Around Tuesday the low will start to weaken, drift northward, eventually rejoin the west-to-east flow, and start to move over the continent. The forcing will remain weak and the moisture transport will be decreased, allowing for only light precipitation during this time.

Below is the latest upper-level pattern forecast from the European model. You can get a good idea of the journey this low pressure will take this weekend through early next week.

Here is an early look at the totals for the second storm. I wouldn't put too much stock in the exact location of the heavier snow just yet.

I will have more information on this storm in Monday's post.

Some more light snow is possible later next week while the next strong storm could arrive next weekend. The models are not in agreement on that system, however, so its a low confidence scenario at this time.

Next update on Monday.

Thanks for reading the South America Daily Snow!

Luke Stone (@imlukesnow)
Forecaster, OpenSnow

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