Chris Tomer’s First Mountain Weather Update for Fall: El Niño, Tropical Moisture, and What Ski Areas Should Watch

# Overview Meteorologist Chris Tomer issued his first mountain weather update for fall on September 1. He described an unusually active pattern driven by a powerful El Niño and exceptionally warm equatorial Pacific waters. That pattern is expected to steer repeated tropical moisture into the western United States through September and possibly into the fall and early winter months.

# What Tomer said about the current pattern Tomer linked the persistent moisture feed across the West to El Niño and the warm waters in the equatorial Pacific. Those conditions are helping generate a stream of tropical moisture that has already contributed to heavy rainfall and flash flooding in parts of southern Utah and northern Arizona.

He expects that September will remain unusually wet across much of the West, with multiple rounds of moisture moving into regions including Utah, Colorado, Arizona, Wyoming, Idaho, and Montana. Short-term impacts include increased rainfall, localized flooding, and higher river and stream flows in affected basins.

# Short-term mountain impacts (next 10 days) Colorado mountain areas are forecast to receive substantial rainfall during the coming 10 days. Utah's Wasatch and the High Uintas also face meaningful precipitation. Tomer named specific resort areas that could be affected: Park City Mountain, Deer Valley, Snowbird, Alta, Vail, Breckenridge, and Aspen Snowmass.

Expect rain at lower elevations and mountain rain that can cause runoff and flash flooding in steep terrain. Recent monsoon moisture set the stage by saturating soils in parts of the Desert Southwest and southern Utah, so additional heavy rain poses an elevated flash flood risk in those zones.

# What this means for the upcoming ski season Tomer stressed that while the immediate focus is rain rather than snow, the broader Pacific pattern is relevant for ski-season prospects. He expects El Niño to strengthen into late fall and possibly peak in November or December.

His outlook leans toward an active, wetter-than-normal winter for portions of the Sierra Nevada and the southern Rockies. Regions specifically favored for increased moisture include Arizona, southern Utah, southern Colorado, and New Mexico. The signal is not an absolute guarantee of heavy snow everywhere, but it indicates greater odds for above-average moisture in those areas.

September should continue wet across much of the West. In October the moisture pattern could shift deeper into the Intermountain West, changing which basins and resorts receive the bulk of storms.

# Immediate safety takeaways

• Resorts and mountain communities should monitor river and drainage forecasts as soils and streams respond to repeated rainfall.
• Travelers should expect weather-related disruptions where heavy rainfall impacts roads and visibility.

# Visual and recent evidence Tomer pointed to dramatic footage of rapid flash flooding through Zion National Park as an example of how quickly conditions can change when monsoon and tropical moisture interact with Western terrain.

# Bottom line A strengthening El Niño and unusually warm equatorial Pacific waters are likely to keep the West in a wetter-than-normal pattern through September. That increases short-term flood and runoff hazards and raises the chances that parts of the Sierra Nevada and southern Rockies will see an active winter. Mountain users and resort operators should track forecasts closely as moisture rotates through different regions over the coming weeks.