Updated: July 28, 2025 – This is an Outlook, not a Forecast!

🔭 Overview

The early signals for the upcoming winter are aligning in favor of an active and colder-leaning pattern across the Central Sierra. As of late July, we’re tracking a combination of:

• ENSO-Neutral trending toward Weak La Niña

• Negative QBO (easterly winds)

• Strongly negative PDO

• Solar Cycle 25 peaking (Solar Max)

This climate setup historically supports above-average snowfall more often than not, with colder storm systems, and an extended spring snowpack from Mammoth to the Bishop Creek zone. Aka skiing into June.

🌊 ENSO: Neutral Now, But Leaning Toward La Niña

• The tropical Pacific remains in ENSO-Neutral territory, with Niño 3.4 temps around −0.2°C.

• Forecast models suggest a 40–45% chance of a weak La Niña developing by fall/winter.

• Odds for ENSO-Neutral holding through winter are slightly higher (~55%).

🌬️ QBO: Negative Phase Taking Over

• The QBO (Quasi-Biennial Oscillation) is trending negative, with easterly winds descending into the stratospheric layer that influences winter circulation.

• Negative QBO often leads to Arctic and Greenland blocking, allowing colder troughs to dig into the West Coast. The -QBO is also known to bring about more extended periods of ridging, also referred to as the infamous 3-week dry cycles that occur in some years.

This signal, along with the others I’m listing, aligns with analog winters like 2005–06 and 2010–11*, both of which delivered over 600 inches of snow at Mammoth Mountain. *However, 2011 was a strong, not a weak, La Niña.

🌊 PDO: Strongly Negative Pattern

• Sea surface temperatures in the North Pacific show a classic cool horseshoe shape — a hallmark of a negative PDO phase.

• This configuration supports a deep Aleutian Low and encourages storm delivery into California.

🧊 Cold storms, lower snow levels, and frequent troughs are more common during negative PDO winters in the Sierra. 

☀️ Solar Max: Solar Cycle 25 Peaking

• Sunspot activity is at its peak — known as the Solar Maximum.

• A stronger sun can enhance the subtropical jet stream, especially when paired with neutral or weak La Niña conditions.

This can increase storm moisture content, fueling deeper dumps when systems do hit the Sierra.

🔁 Analog Year Snapshot

📆 Seasonal Breakdown

🍂 Fall (Oct–Nov)

• Cut-off low season — dry stretches mixed with quick-hitting systems.

• Potential for early elevation snow in October or early November.

❄️ Winter (Dec – Feb)

• January – February looks to be the core storm window.

• Expect multiple cold troughs, atmospheric rivers, and low snow levels.

• February could be the peak action month.

🌷 Spring (Mar–May)

• Based on analogs, a strong finish is likely.

• March and April storms could reload the upper elevations.

• Runoff season may extend into June, especially from Mammoth Crest to Bishop Creek.

✅ Final Takeaway 

If La Niña sets up into a weak phase — and the QBO and PDO patterns hold, the Central Sierra has a strong chance for a colder, snowier season, especially during mid to late winter. This could be another backloaded season with excellent snowpack potential from Mammoth to Bishop Creek.

However, if ENSO remains in a neutral state through the winter, the storm track may become less consistent early on, with a greater chance of dry spells between storms.

Even then, the alignment of negative QBO, negative PDO, and Solar Max still leans the pattern toward a cooler and wetter bias compared to a typical neutral year, especially from January through March in the upper elevations.

Please also remember this is an OUTLOOK, NOT A FORECAST. Many of the trends we look for to gauge what type of winter may be upcoming don’t develop until November or December.

Over my 40 years of watching and being involved with the weather here in Mammoth. I have seen the perfect setup result in a drought year, and the same with a poor-looking pattern that turns out to be a bit above average. 

Over the next few months, my hope is that the ENSO will transition into the weak La Niña Territory. I think that would be our best chance at getting some decent snowfall this winter into early next spring.

Ski Ya Later, Snowman Out