Mammoth Mountain
Weather Forecast
Mammoth Mountain,Mammoth Lakes, Crowley, and Bishop.
Mammoth Mountain Weather Discussion
Tuesday, October 7, 2025 @ 4 PM
Setup / Today–Thursday
A cutoff low remains parked off the Central California coast, detached from the jet. As it drifts a bit farther west, 500-mb heights trend back toward climatology, allowing temperatures to recover to near seasonal averages. Expect light winds and clear skies.
Late Thursday into Saturday: By late Thursday, a stronger low-pressure system organizes near the southern Oregon / far-northern California coast, then tracks east along the Oregon-California border late on Friday into Saturday.
Impacts for Mammoth: Cooler temps, breezy conditions, and limited moisture given the northern track.
QPF signal: ECMWF still paints ~0.10″ over the crest, enough for a couple of flakes at the highest elevations, but most moisture stays north.
Sunday–Early Next Week: Model Split
Guidance shows a second low dropping through WA into OR on Sunday.
ECMWF idea: The low slides off the coast near San Francisco afterward. That coastal placement, with orographic lift, would be favorable for snowfall in the Central Sierra.
GEFS/NBM idea: A more inland “slider/hybrid” look — colder, breezy, lighter totals versus the ECMWF’s more productive solution.
Translation: Snow potential is on the table, but track and coastal vs. inland evolution will decide whether we’re talking a nuisance coating or something more meaningful.
Snowman’s Take
We’re expected to be breezy and cooler late in the week, with minimal precipitation. Sunday–Tuesday is the watch window: if the low stays near the coast, Central Sierra snow chances improve; if it slides inland, expect lighter, colder, and windier conditions. It’s October — models wobble in transition season — so stay flexible and enjoy the build-up.
Steve Taylor, the Mammoth Snowman (WX Links)
Images provided by WeatherBell.com
NOAA 6-10 Day & 8-14 Day Outlooks
October Seasonal Model Update – Looking Toward Winter 2025–26
10-5-25 @ 5 PM – The latest ECMWF seasonal update just dropped, and we’ve dug through every chart and model trend to see what this winter might bring to Mammoth Mountain.
The signal this year? A weak La Niña that fades fast — a setup that often means a slow start, followed by a better shot at storms once the pattern relaxes.
That’s a familiar pattern in the Eastern Sierra. Early winter can run lean while the Pacific jet stays aimed a bit north, but once it sags south, things can change in a hurry.
The key question this year isn’t whether storms will come — they will — but when the pattern opens the door and how cold those early ARs run.
Looking for years to match this Fall is tough. Here are the ones that are the closest: 2000-01 (393), 2005-06 (579), 2016-17 (618), and 2017-18 (262).
I will have more information on this in a couple of days, once I have concluded my research on past patterns.
Snowman – Next Model Update on 11/5/25
❓ Top Mammoth Weather Questions (from the Snowman)
When does Mammoth usually get its first snowfall?
Light snow can fall in late September, but consistent snowfall usually begins in late October or early November. Opening Day typically lands between November 10 and Thanksgiving, depending on storm activity and snowmaking.
How does the ENSO pattern affect Mammoth’s late fall and winter weather?
ENSO (El Niño/La Niña) plays a big role in Sierra storm patterns. El Niño winters often bring warmer, wetter storms. La Niña typically favors colder, backloaded seasons with more snow from February through April. Neutral years are the wildcards with high variability.
What is 500mb height and why does it matter?
500mb height maps show atmospheric pressure around 18,000 feet — a critical layer for tracking storm tracks, ridging, and jet stream placement. Watching 500mb patterns helps forecast Mammoth’s incoming storms and long-range trends.
What are the PNA and PDO, and how do they affect Mammoth weather?
The PNA (Pacific-North American Pattern) influences western U.S. ridging and troughing. A negative PNA favors cold, stormy setups. The PDO (Pacific Decadal Oscillation) affects sea surface temperatures in the North Pacific — a negative PDO often aligns with enhanced storm delivery into California during winter.
👉 Want more answers? Check out the full Mammoth Weather FAQ – 50 Expert Answers to learn more about storms, snow, winds, and long-range patterns from a trusted local source.
Author Bio: Steve Taylor, The Mammoth Snowman. Over the last 40+ years, Steve has spent countless hours studying and learning about Mammoth Mountain Weather and Snow Conditions.
Dr. George, Don Marcelin, Howard Sheckter, and Ted Schlaepfer were his weather mentors at that time. Steve used to hang out with Howard in the Weather War room in the early ’90s, getting first-hand knowledge of Mammoth Weather from the (The Dweeb) himself.
Steve has spent countless hours reading, studying, and watching weather discussions from the NWS and multiple Private Weather Forecasters. He is a long-time member of WeatherBell, Weather West, and AccuWeather Pro. Disclaimer: Steve is a hobbyist forecaster with over 35 years of experience reporting recreational weather and travel reports for the Mammoth Lakes area.