As the first flakes begin to fall in the mountains and the air turns crisp, our excitement for the upcoming ski season builds, as we’re sure yours does too. At Powderchasers, we're committed to guiding you to the deepest powder possible. Let's dive into the atmospheric patterns and oscillations that will shape this winter across the United States.
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El Niño Southern Oscillation (ENSO)
Understanding ENSO: ENSO is an oscillation characterized by variations in sea surface temperatures in a region in the equatorial Pacific just off the coast of Peru. It oscillates between:
- El Niño (Positive Phase): Warmer-than-average SSTs in the region
- La Niña (Negative Phase): Cooler-than-average SSTs
- Neutral Phase: SSTs near average
These phases influence the jet stream's position and strength, significantly impacting weather patterns across North America. A positive phase amplifies the Pacific jet while the negative phase typically shifts the storm pattern further north with a polar jet amplification.
Current State and Forecast: Last season was a positive ENSO phase (El Niño) and we saw the effects. The PNW struggled, with most resorts ending with around 70% of their average seasonal snowfall. Resorts in the southwest US had a good season, right around average. Resorts in the northern Rockies struggled with the amplified Pacific jet, while the Rockies further south in areas like Utah and Colorado finished near and above average.
Currently, we're in a slightly negative phase, indicating the onset of La Niña conditions. Forecast models predict La Niña will strengthen as we head into winter, with SST anomalies reaching around -1°C during the peak of the season.
Impact on Snowfall: A moderate La Niña, which is what we’re looking at with SST anomalies in the -1C range, typically leads to:
- Pacific Northwest & Northern Rockies: Enhanced storm activity due to a northward-shift in the jet stream, resulting in heightened chances for above-average precipitation and cooler temperatures.
- Southwest & California: Drier and warmer conditions, potentially leading to below-average snowfall.
- Central Rockies: Variable conditions, with storm tracks occasionally dipping south enough to bring significant snowfall.
- Northeast: Slightly above average moisture possible with an edge towards warmer conditions. The Northeast is less impacted with drastic changes from El Nino or La Niña.
Overall, La Niña phases often bring increased storm frequency, meaning seasons characterized by a negative ENSO phase often see small, frequent dumps rather than sporadic, massive atmospheric rivers.
Pacific Decadal Oscillation (PDO)
Understanding PDO: The PDO is a long-term oceanic pattern of Pacific climate variability, shifting between warm (positive) and cool (negative) phases over 20-30 years.
Current State and Forecast: We are currently in a strongly negative PDO phase, expected to persist throughout the season. This phase features:
- Cooler SSTs along the West Coast of North America
- Warmer SSTs in the central North Pacific
Impact on Snowfall: A negative PDO often complements La Niña conditions by:
- Enhancing the northward-shifted jet stream, increasing storm frequency and intensity in the Pacific Northwest and Northern Rockies
- Potentially reducing precipitation in California and the Southwestern states, though occasional strong storms may still occur
Quasi-Biennial Oscillation (QBO)
Understanding QBO: The QBO is a regular variation of stratospheric winds above the equator, alternating between easterly (negative) and westerly (positive) phases approximately every 28 months. It influences the behavior of the polar vortex and jet stream patterns.
Current State and Forecast: After a negative (easterly) phase last winter, a new westerly QBO phase is descending and strengthening, confirmed by recent weather balloon data from Singapore showing westerly winds at the 10-70mb levels.
Impact on Snowfall: A westerly QBO phase often leads to:
- A stronger and more stable polar vortex, which can limit the southward movement of Arctic air
- Milder winter temperatures across much of the United States
- Potentially fewer cold outbreaks, but when they do occur, they can be intense but short-lived
Madden-Julian Oscillation (MJO)
<mjo image>
Understanding MJO: The MJO is an eastward-moving disturbance of clouds, rainfall, winds, and pressure that traverses the planet in the tropics and returns to its initial starting point every 30 to 60 days.
Current Influence: Recent forecasts from long-range models suggest that Phases 4 and 5 of the MJO will likely dominate this winter. These phases are characterized by:
- Increased convection and precipitation over the Maritime Continent and Western Pacific
- Atmospheric patterns that can suppress sustained cold air intrusions into the Eastern United States
Impact on Snowfall: Dominance of MJO Phases 4 and 5 can lead to:
- Milder temperatures in the Eastern US, reducing the likelihood of prolonged cold spells.
- Enhanced storm activity in the Pacific Northwest, benefiting ski regions in that area.
- Potentially drier conditions in the Southern US, affecting snowfall in those regions.
Summary: Regional Snowfall Outlook
Pacific Northwest (Washington, Oregon):
- High confidence in above-average snowfall due to the alignment of La Niña, negative PDO, and warm North Pacific SSTs.
- Frequent storm systems are expected to bring consistent powder days.
Northern Rockies (Idaho, Montana, Wyoming):
- Anticipate a robust snow season with colder temperatures and abundant precipitation.
- Ideal conditions for deep snowpack and prolonged ski seasons.
- Frequent, small dumps should characterize the season for these regions
Central Rockies (Utah, Colorado):
- Near-average snowfall is expected, with potential for significant storms when the jet stream dips south.
- Consistent, smaller dumps for areas further north in this region
- Variable conditions, even a few miles could make a big difference, but opportunities for excellent skiing should arise for resorts in this region throughout the season
Sierra Nevada (California):
- Potential for below-average snowfall, as the storm track may remain north.
- Occasional strong storms could still deliver substantial snow, so remain optimistic.
- Strong but infrequent systems if there are short-lived periods of Pacific jet amplification are the only way CA can stay near average
Southwest US (Arizona, New Mexico):
- Likely to experience drier and warmer conditions, resulting in limited snowfall.
- Plan for alternative activities, but keep an eye out for rare snow events if the Pacific jet gets fired up (~1.5 week forecast lead time)
Eastern United States:
- Warmer-than-normal temperatures are expected overall.
- Potential for brief but intense cold spells
- Snowfall will be less frequent, but major events could still occur.
Disclaimer: This forecast is based on current models and historical patterns. Long-range weather predictions involve uncertainties, and actual conditions may vary. We recommend keeping an eye on updated forecasts as the season progresses.
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