Mammoth Mountain Weather Forecast Discussion 

9-8-25 @ 1 PM – A taste of Fall is on the way with two low-pressure systems approaching the area over the next week.

The first system is a moderate strength low that is expected to move into central California on Wednesday. This one is a slow mover, and the back side of that system, as of now, won’t come through until late Thursday afternoon or evening.

There is some moisture associated with System One, so expect to see some rain and possibly very light snow showers, at least on the top webcams at Mammoth, from this system.

The second system arrives on Sunday from the west with minimal moisture, bringing more cooler air for a continued taste of Fall into at least day 7. The second system’s track and what moisture it has to work with are low confidence as of this post.

7day-ecmwf-deterministic-nepac-z500_anom

Here is the newest ECMWF MSLP (12Z) for next Wednesday, Thursday, and Friday. All three days offer a chance of afternoon showers and occasional thunderstorms. 

ecmwf-deterministic-sierras-instant_ptype

The QPF continues to be on the weak side, but we will take it. Hopefully this system gets wetter and drops some much-needed rain over the Garnet Fire.

qpf-ecmwf-deterministic-sierras-total_precip_inch

Temperature Anomaly: The gif below really tells the story of the temperatures this week. Those blues mean well below the average for this time of year. This weather is more like mid-October days. Enjoy it, as it will warm up again for a few days in the extended forecast before the next surprise might move in. 

wed-temp-anomaly-ecmwf-deterministic-nepac-t850_anom_streamWinds will increase in the afternoons with gusts in the 25-35 mph range over higher elevations during the afternoon and evening hours. Lower elevations will see winds in the 10-20 MPH range.

ECMWF 12Z WInds-2025-09-08_12-08-57

Yes, there is even some very, very light snowfall forecasted with this system. Snowfall levels will be above 10,000 to 11,000 feet. If snow does fall, it will, for the most part, melt on contact. There may be some areas under a thunderstorm that might receive a brief light dusting, but it won’t last long. 

snow_ecmwf-deterministic-sierras-total_snow_Days 7 through 10 on the ECMWS ENS below show a break in the action, with at least a couple of days of higher heights followed by some more weak troughing, similar to what we have been seeing over the last few months. 

 Have a great day and enjoy the Eastern Sierra Weather!

— Steve Taylor, the Mammoth Snowman (WX Links)

Images provided by WeatherBell.com