LONG RANGE FORECAST DISCUSSION

Issued 19 Feb 2025, 12Z

Hello! Welcome to our first-ever LFD (Long-Range Discussion) post! We are going to be talking about what the weather will hold for us in the long run (next couple of weeks). We won’t be doing this very often due to how difficult and complex it is to forecast conditions far out, but this is a fun thing for us to work on and improve.

Weather Regimes

We are currently in a Greenland High, which has been allowing all this storm activity and long periods of frigid air to be funnelled through Southern Ontario as cooler Arctic air is brought down south. However, this is going to change soon as we shift quite rapidly into a Pacific Trough-dominant regime by next week. This will cause cooler and moist air from the Pacific Ocean to move into North America, increasing cloud cover and precipitation and bringing below-average temperatures, while the West will experience the opposite. Afterwards is where it gets quite tricky, models are giving mixed signals with a high pressure due to form over the Pacific Ocean, the location of this high pressure will determine our weather pattern with either a Pacific Ridge and an Alaskan Ridge regime developing, both of which will give nearly completely different weather conditions, if you like snow and the cold, you would want the Alaskan Ridge, as the high pressure will be centred over Alaska and essentially squeezes the jet stream from the west, forcing all this Arctic air down south and onto Central and Eastern Canada, this will also increase snowfall as the warm and cool air collide. On the other hand, if a Pacific Ridge were to develop, it should typically have the high pressure system centred further southwest, blocking the flow of Pacific moisture and will lead to drier and warmer conditions, due to the lack of moisture it will also create more stable weather with only minimal storms impacting the region.

Teleconnections

The PNA (Pacific North American Oscillation) is currently positive and looks to remain positive till Early March, meaning that we will likely see cooler-than-normal temperatures until late this month as conditions will begin to change, this will continue the potential of storms to develop but due to the dissolving Greenland High regime will likely bring weaker storms as the Arctic won’t be as forced down south as before, I believe Alberta clippers are more likely to impact Southern Ontario due to this. The AO (Arctic Oscillation) is negative and is expected to rise sharply into the positive value, when the Arctic Oscillation is negative it brings typically cooler-than-normal temperatures to the East as cold air is pushed down south due to a High Pressure up in the Arctic, but as it trends positive this pattern is set to reverse, allowing the warm air to rise north more easily, reinforced with the PNA+ will still allow the dry and cool Arctic air to move over the region but won’t be as significant.

Summary

Stormy weather and freezing Arctic temperatures have been brought to southern Ontario by a Greenland High, but that is about to change. A Pacific Trough will take control by the following week, bringing with it more clouds, precipitation, and lower-than-normal temperatures. In the event that a Pacific Ridge forms, we can anticipate drier, warmer, and more stable weather; if an Alaskan Ridge forms, we’ll see more cold and snow. While the AO (Arctic Oscillation) flipping positive could bring a gradual warm-up, the PNA+ (Pacific North American Oscillation Positive) indicates that we will remain cooler until early March. Over the next few weeks, snowfall is possible due to the fast-moving Alberta Clippers.

DISCLAIMER: This long-range forecast is based on current trends and model predictions, which can change quickly. While we do our best to provide accurate forecasts, weather this far out is highly uncertain—so take it with a grain of salt!