Mammoth Mountain Weather Forecast
Including Mammoth Lakes & Bishop, California
Wednesday, September 18th at 10 AM – Mammoth Mountain and the Southern Eastern Sierra are under cloudy to partly cloudy skies. On Tuesday, snow fell in the Rock Creek Canyon area (3-6 inches) and at the June Mountain Ski area (1-2 inches).
The Mesa and Bishop Creek Canyon also received a couple of inches of snow. So far, Mammoth Mountain has missed out, with just a few flakes passing through.
Checking area weather stations this morning, up top, the temperature is 34 degrees with an SSW wind at 1 MPH gusting to 3 MPH. At the Main Lodge / 8900 elevation level, the temperature is 42 degrees, with an ENE wind at 1 MPH, gusting to 3 MPH at times.
The temperature in Mammoth Lakes is 46 degrees. The Mammoth Airport is 48 degrees, with 49 degrees in Crowley Lake and 59 degrees in Bishop.
Weather Forecast for Your Adventure
Wednesday through Thursday: There is a 50% chance of rain, snow showers, and a few thunderstorms. There is an 80-90% chance of light rain and snow tonight and into Thursday.
Snow levels will be around the 9,500 to 10,500-foot level. Snowfall accumulations will be limited to the upper mountain, with a dusting of slop to possibly an inch above the 10,000-foot level.
A light shift in this system’s track could bring in slightly cooler temperatures. If that happens, snow levels will decrease a bit more, and accumulations will increase.
If one of those thunderstorms moves over the mountain, you can expect more snowfall and lower snow levels for a time.
Basic Weather Details for your Outside Adventure: Wednesday into Thursday: For the Main Lodge / 8900 Feet, midday temperatures at the 8900-foot level will be in the upper 40s to low-50s today and the upper 30s to lower 40s on Thursday. Overnight lows will be in the upper 30s to mid-40s.
The wind forecast calls for SW breezy at 5-10 MPH, with gusts up to 25-35+ MPH from Main Lodge up to the top of the Mountain
Midday temperatures in Mammoth Lakes will be in the mid-50s on Wednesday and in the upper 40s to lower 50s by Thursday. Overnight lows will be in the upper 30s to lower 40s.
For Bishop to Mill Pond, mid-day highs will be in the upper 60s to lower 70s, with overnight lows in the low to mid-40s.
The Weekend Outlook Friday into Sunday: Mammoth Mountain and the Southern Eastern Sierra will clear out with warming temperatures and decreasing winds. Mammoth Lakes will be in the mid-60s during the afternoons, with Bishop in the low to mid-80s. It sounds like a perfect weekend for a nice adventure.
Mammoth Mountain & Eastern Sierra Weather Discussion & Outlook
The next September low-pressure system is working its way into the area today. This one is a bit weaker than the last one and also slow mover.
As it has slowed, the low has also tapped into a small amount of subtropical moisture. Snow levels will be higher now than forecasted a couple of days back due to the weakened strength and the warmer subtropical moisture now embedded in the system.
This morning, I looked at all the HRRR, ECMWF, and GEFS data. They all have weak QPF for this system. The average of all models is 30-.50, which is spot on what the ECM ENS shows.
As far as snow goes, snow levels have crept up to 9,500 to 10,500 feet in elevation. Snowfall at the Summit could still be in the 1-2 inch range. With the warmer nature of this system, snow accumulations look limited to a dusting.
September storms are usually weak regarding snowfall; in most cases, Mammoth Mountain sees just a dusting. For some unknown reason, the September system favors Rock Creek Canyon.
Hopefully, over the next 36 hours, all of the Southern Eastern Sierra picture will receive rain, helping to reduce the fire risk this Fall.
Longer Range Fantasy Outlook 6-14 Days and then out 45 Days
The 6-14-day forecast period is looking warm and dry as a new ridge of high pressure moves into the area early next week. This ridge looks to be fairly strong, so expect a nice warm-up.
Since it’s the latter half of September, days are shorter, and the sun is lower in angle, temperatures will not be as warm as if this ridge came during the summer months. With that said, it looks like the 70s next week for Mammoth Lakes, with Bishop in the upper 80s, maybe even a 90 later in the week.
Looking way out into the Fantasy Forecast period for October’s weather trends, the ensemble models still show warmer and dryer days overall.
The one thing that could change is that a typhoon would merge with the westerlies and send some moisture our way. That weather pattern is more likely for Mammoth from mid-October to early November.
Steve Taylor – the Mammoth Snowman
The next full Mammoth Weather Forecast Update will be Friday by 5 PM.
Mammoth Weather Forecast Data from Weather Bell
ECM & GEFS Ensemble Models 500
15-Day ECM 500mb Anomaly GIF: Below is the entire 15-day run of the ECMWF ensemble model. I use this model to tell the Mammoth Weather Story you just read above. Compared to the other models, this solution has been effective more often than others over the years.
16-Day GEFS Ensemble 500mb Anomaly GIF: Below is the second most trusted ensemble model that we use that goes out to day 16. Model relaibily beyond day 7 can be very suspect expecialy during the transition seasons of Spring and Fall.
ECMWF Ensemble Jet Stream Gif
This is the Eastern Pacific View of the ECMWF ENSEMBLE Run of the Jet Stream.
Temperature Forecast
Temperature Anomaly GIF:
*Temperature anomaly means a departure from a reference value or long-term average. A positive anomaly indicates that the observed temperature was warmer than the reference value, while a negative anomaly indicates that the observed temperature was cooler than the reference value.
The Wind Forecast
QPF Forecast
Snowfall Forecast
Precipitable Water Anomaly
45-Day Long Range Fantasy Outlook
This is the long-range ultra fantasy 45-day model run. These longer-range ensembles are good for examining long-range trends in the overall weather pattern. They should never be used or considered a forecast.
46-Day Fantasy Snowfall Outlook
First Look at Snowfall Season 2024-25
9-5-2024 – When looking ahead to the next snowfall season, predicting what might happen is difficult at this time of year. If a weak La Nina does form (66%), there is a good chance we will have a drier-than-average snowfall season.
However, several very big winters have come from weak La Ninas over the last 25 years. (See the La Nina Winter chart down the page.) Everyone must also remember that many other factors are at play than just warm or cooler water along the Pacific equator.
For now, Ted (Powder Forecast) and I are not forecasting what the winter might be like. We will better understand how this may play out in late October / early November. As we have all seen in the past, patterns can quickly flip and change in late December and January.
La Nina seasons are like El Nino and can bring drought, moderate winters, or large ones. Many factors are at play, and the situation can change as the winter season starts to ramp up in mid-to-late December.
Let’s keep the positive vibes that Mammoth Mountain gets a perfect winter, with moderate amounts of powder snow mixed in with some dry periods and endless wind-buff days.
Steve Taylor – The Mammoth Snowman
PS The new runs of the ECMWF Seasonal come out for forecasters on the 5th of each month.
La Nina Years Snowfall Totals for Mammoth Mountain
Weak La Nina
1971-72 Snowfall Total = 268 with 139 in December
1984-85 Snowfall Total = 236
2000-01 Snowfall Total = 393 with 124 in February
2005-06 Snowfall Total = 578 with 4 100+ inch snowfall months
2008-09 Snowfall Total = 470 with 2 100+ inch snowfall months
2016-17 Snowfall Total = 617 with 245 January 163 February
2017-18 Snowfall Total = 262 with 142 in March
Moderate La Nina
1970-71 Snowfall Total = 255
1995-96 Snowfall Total = 321
2011-12 Snowfall Total = 263
2020-21 Snowfall Total = 244.5
2021-22 Snowfall Total = 260
Strong La Nina
1973-74 Snowfall Total = 306
1975-76 Snowfall Total = 197
1988-89 Snowfall Total = 251
1998-99 Snowfall Total = 323
1999-00 Snowfall Total = 382
2007-08 Snowfall Total = 333
2010-11 Snowfall Total = 668
2022-2023 Snowfall Total = 717 – Largest Winter Recorded over the last 100 years
ENSO Watch
Most Recent Posts
Mammoth Mountain Weather Forecast & Discusion
Mammoth Mountain Weather Forecast & Discusion
*Mammoth Mountain and Eastern Sierra Weather is updated Sunday, Tuesday & Thursday by local Steve Taylor, the Mammoth Snowman. The goal is to provide detailed weather forecasts presented in an easy-to-read format. This isn’t a Hype, one-and-done model-run website. It’s just the basic facts from how I see it after 40 years of being involved in local weather and recreation. And yes, I use Weather Bell for my forecasting data.
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Author – Steve Taylor – The Mammoth Snowman – Over the last 30+ years, Snowman has spent countless hours studying and learning about Mammoth Mountain Weather and Snow Conditions first hand. He has been skiing around the hill with marked ski poles since March of 1991 so he can measure the fresh snowfall amounts out on the hill.
Snowman started blogging this information back in 1990 on the old Mammoth BBS system, then the RSN Forums, and then on to MammothSnowman.com in 2004 with Video and photo Blog reports. (There was No YouTube back then.) Facebook was added to the fold in 2008, and the Facebook Group was added in 2016.
Reports, videos, and photos from the website have been featured on local TV Stations here in Mammoth and Bishop, as well as KTLA, AP, Fox, ABC, CBS, and NBC News.
Click Here to Learn More About the People Who Make MammothSnowman.com a Reality