Winter 2024/2025 Forecast: La Niña’s Influence Expected to Shape Cold Weather Patterns

The preliminary forecast for the Winter of 2024/2025 is influenced significantly by a weak La Niña phase. This phase is expected to alter the typical jet stream patterns over North America and the Pacific Ocean, affecting weather conditions across the globe. A potentially weaker-than-normal Polar Vortex is also being closely monitored for the early part of the winter season.

Global weather systems are driven by a combination of large-scale and small-scale factors, with the weak La Niña event in the Pacific being the primary driver this year. The Polar Vortex, which typically becomes more active during winter, will also play a significant role in determining weather patterns.

In previous La Niña winters, a blocking high-pressure system over Greenland and the North Pacific has been observed, with low pressure and colder air extending from western Canada into the United States. In Europe, a cutoff low-pressure area often brings cold and snowy conditions to central regions.

Emergence of a Weak La Niña

La Niña, characterized by cooler-than-average sea surface temperatures in the central and eastern Pacific Ocean, is the cold phase of the ENSO (El Niño-Southern Oscillation) cycle. The ENSO cycle oscillates between La Niña and El Niño, the latter being the warm phase.

Recent data from NASA’s mid-August ocean anomaly analysis reveals colder-than-normal surface waters in the central and eastern ENSO regions. These cold anomalies, shaped by strong easterly trade winds, are indicative of the early development of a La Niña phase.

Forecasts from the NMME (North American Multi-Model Ensemble) suggest that these cooler anomalies will persist through the autumn and winter of 2024/2025. The forecasted cooling remains within the La Niña threshold, though it appears weaker than earlier predictions.

Despite a relatively weak La Niña event, this oceanic condition will still influence the positioning of the jet stream during winter, affecting weather patterns across North America and beyond.

Winter and the Polar Jet Stream

Historical data from past La Niña winters provides valuable insights into how such conditions might affect the upcoming winter. Each ENSO phase exerts a substantial influence on tropical rainfall, pressure patterns, and the energy exchange between the ocean and atmosphere. The interaction between these factors drives global weather patterns, particularly in the Northern Hemisphere during winter.

The circulation pattern during La Niña typically features a strong high-pressure system in the North Pacific and low-pressure systems over Canada and the northern United States. A similar low-pressure area is often observed over southwestern Europe. This pattern tends to push the jet stream southward, bringing colder air and winter storms from the polar regions into the northern and northwestern United States.

As the jet stream shifts, colder and wetter conditions become more frequent in the northern United States, while the southern states often experience warmer and drier weather. The cold air is more accessible to the northern regions, increasing snowfall potential when moisture is present.

Analysis of the average temperature and snowfall patterns during weak La Niña years suggests that this winter could see increased snowfall in the northwestern United States, the Midwest, and parts of northeastern United States and eastern Canada.

Winter 2024/2025 – ECMWF First Forecast

The first look at the winter forecast for 2024/2025 involves three key seasonal models: the ECMWF (European Centre for Medium-Range Weather Forecasts), the CanSIPS (Canadian Seasonal and Interannual Prediction System), and the NMME. These models provide an average picture of weather patterns over the three meteorological winter months (December, January, and February).

The ECMWF model indicates a prominent La Niña high-pressure system over the North Pacific and a low-pressure area over Canada. This configuration pushes the jet stream into the northern and northwestern United States, while in Europe, the jet stream is nudged further north due to the high-pressure system.

The ECMWF model also shows a broad high-pressure area covering the tropical Pacific, confirming La Niña’s influence on surface-level circulation and atmospheric conditions. As a result, Europe is expected to experience warmer-than-normal temperatures, particularly in regions influenced by the high-pressure system.

In terms of precipitation, Europe is likely to see drier conditions in the west due to the high-pressure anomaly, while the rest of the continent may experience above-average precipitation. Over North America, the ECMWF forecast predicts colder surface temperatures in western Canada and warmer-than-normal conditions in the southern United States.

A closer look at the January 2025 forecast reveals a potential break in the above-average temperature anomalies, indicating a possible route for cold air outbreaks in the central and Midwest regions of the United States.

ECMWF Winter 2024/2025 Snowfall Forecast

The ECMWF snowfall forecast for the winter of 2024/2025 shows below-average snowfall across much of Europe, with the exception of Scandinavia, where increased snowfall is expected due to the influence of a local low-pressure system.

In North America, the forecast indicates below-average snowfall for most of the United States, particularly in the Midwest and Northeast, regions that typically receive more snow during weak La Niña winters. However, more snowfall is anticipated in the western and northwestern United States and parts of central and eastern Canada. It’s important to note that this forecast does not yet include data for February, which could alter the overall snowfall outlook.

CanSIPS Winter Season Forecast

The CanSIPS model, developed by the Canadian Meteorological Centre, supports the weak La Niña pattern, with a high-pressure zone over the North Pacific and a low-pressure area over Canada. Additionally, a high-pressure area is forecast over northwestern Europe.

The temperature forecast for Europe suggests warm anomalies across much of the continent, with a belt of normal to colder temperatures in central regions due to easterly flows outside the high-pressure zone. In North America, the CanSIPS model predicts above-normal temperatures across the southern United States and colder-than-normal conditions in southern Canada and parts of the northern United States.

For February 2025, the CanSIPS model shows cold air anomalies extending further south into the northern United States, suggesting a slower start to winter across the central and eastern regions, with more snowfall potential in the latter part of the season.

The precipitation forecast from CanSIPS mirrors that of the ECMWF, with drier-than-normal conditions expected in much of Europe and the southern United States, while more precipitation is forecast for the northwestern United States.

NMME Winter 2024/2025 Weather Forecast

The NMME forecast, which combines multiple North American models, reinforces the expected weak La Niña pattern with a strong high-pressure system in the North Pacific and a low-pressure system over Canada. This pattern pushes the jet stream down over the northern United States, resulting in normal to colder temperatures in these regions, while warmer temperatures are forecast for central, eastern, and southern parts of the United States.

The NMME precipitation forecast indicates wetter conditions in the northwestern United States and the Midwest, while drier conditions are expected in the southern United States. Canada and the northern United States may also see increased precipitation, in line with a typical weak La Niña winter.

Overall, the Winter of 2024/2025 is expected to feature a “double character” across the United States, with colder conditions in the north and warmer weather in the south, as influenced by the weak La Niña phase.