Mammoth Mountain Weather Forecast & Long Range Outlook
Steve Taylor
September 12, 2024
8:26 am
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Mammoth Mountain Weather Forecast
Including Mammoth Lakes & Bishop, California
Sunday, September 15th at Noon – Storm Update – The next chance for some light snowfall and a dusting of white on Mammoth Mountain will be late tonight into Monday. As of Sunday late morning, snow levels are in the 7500-8500-foot range.
The QPF is relatively weak, and this morning, it is averaging out on the models to .05 to .10. That amount of moisture under a normal 10/1 ratio storm would add up to 1/2 to 1 inch of snow.
If that is the case for tonight and Monday’s system, it will be tough to get a dusting of snow to show up on the webcams. That’s not enough snow when dry dirt has been baking in the sun for the last few weeks.
As of late Sunday morning, I would call the ground to get white at the Summit during this first system moving through a 50/50 chance.
The good news for those wanting to see a dusting of snow is that a second system is coming in later this week. That second system looks more favorable for 2-3 inches of snowfall on Mammoth Mountain. That amount of snow would be enough to make the ground white again on the webcams temporarily.
Some people have been asking if it is normal to get snow around the summer to fall equinox. The answer is not every year, but I have seen it happen multiple times over the years.
If you read this weather blog during August, I always mention the 9/21 time frame starting about a month out as the timing for the first possible dusting.
Steve Taylor – the Mammoth Snowman
PS: There will be a full updated forecast posted on Monday by 5 PM
Saturday, September 16th at 8:30 AM – Mammoth Mountain and the Southern Eastern Sierra are under clear blue skies. When you go outside, it feels like early fall in all locations, with these cooler days upon us.
I checked area weather stations this morning. Up top, the temperature is 44 degrees with a SW wind at 12 MPH, gusting to 14 MPH. Down at the Main Lodge / 8900 elevation level, the temperature is 50 degrees with a SW wind at 2 MPH, gusting to 6 MPH at times.
The temperature is 49 degrees down in Mammoth Lakes. The Mammoth Airport is at 40 degrees, with 40 degrees in Crowley Lake and 54 degrees down in Bishop.
Weather Forecast for Your Mammoth Mountain / Eastern Sierra Adventure
For Saturday into Tuesday at the 8900-foot level (Main Lodge/Mammoth Lakes Basin), skies will be clear Saturday and Sunday, with light rain and snow possible late Sunday night into Monday. Tuesday looks to bring a break in the weather action with clear skies and less wind.
Midday temperatures will be in the mid-60s on Saturday, mid-50s on Sunday, and lower 40s on Monday. Overnight lows Saturday night will be in the 40s, and Sunday night will be in the mid-30s.
Winds on Saturday will be SW at 5-10 MPH, with gusts up to 20+ MPH. Over the upper reaches of the hill, gusts will be up to 30 MPH. For Sunday, winds pick up ahead of the next weather system moving in. Expect gusts in the 45-60+ MPH above the 9000-foot level.
Midday temperatures in Mammoth Lakes will be in the upper 60s to lower 70s on Saturday, with mid-60s on Sunday and upper 40s on Monday. Overnight lows will be in the lower 40s, coming down into the 30s on Sunday Night. Winds will be SW at 5-10 MPH, with gusts to 20+ MPH.
For Bishop to Mill Pond, mid-day highs will be in the mid-80s to upper 80s on Saturday, the mid-80s on Sunday, and the low to mid-70s Monday into Tuesday. Overnight lows will fall into the low to mid-40s. Valley winds on Sunday will be 15-25 mph, with gusts in the 35-40 MPH range.
Mammoth Mountain Weather Outlook & Discussion
Weather Discussion through next Friday: One more day of clear skies with light winds in the area. On Sunday, the next upstream low-pressure system will start to affect Mammoth Mountain and all elevations by the afternoon hours with increasing winds.
Light rain and snow showers are increasingly likely Sunday night into Monday. Snow levels will be above 9000 feet and then drop to the 7500 – 8500 elevation range by Monday around sunrise.
Models still have just enough snowfall for Mammoth Mountain (from Main Lodge up) to see a second dusting of snow on Monday. However, the ground surfaces are warm and dry, so getting a dusting could be challenging with the limited moisture this first system has.
The ECM ENS QPF amount for the Monday cold front is meager, in the .10 range, with some models only showing a trace. That would add up to a dusting of snow at best.
There is a break with clear skies for Tuesday, and then a second system is on tap for Wednesday into Friday. A bit more moisture is showing up this morning for this second system.
The ECM ENS QPF is at .10-.20, and the NBM is at .20-.30. That’s about all you’ll get from a September QPF forecast from a system like this.
This outcome It is pretty typical for this time of year. For those who read these discussions during August, you might recall I have been talking about the time frame around September 21st for a dusting since we had the last dusting on August 24th.
Over the decades, I have watched the weather, and it seems like out of 10, you get 2-3 years when something comes in around 9/21. These lows in 2024 are a bit stronger than what I remember from the past.
Longer Range Fantasy Outlook 10-45 Days: In the longer range fantasy outlook period for the last week of September. The ECM ENS model has higher heights and dry conditions for what would be considered Indian Summer Weather. (That is assuming one of next week’s two systems does bring a dusting to the high country.)
When comparing the GEFS model to the ECM, you see slightly cooler temperatures overall and lower heights in the area. If the area does warm up again, as I expect it to, don’t expect temperatures to be hot like in the Summer months.
Looking into the Fantasy Forecast period for October’s weather trends, the ensemble models still show warmer, drier days.
One of the patterns that could change that outcome would be a Typhoon merging with the westerlies and sending some moisture our way. When it happens, that type of weather pattern is more likely for Mammoth from around mid-October into early November. If that pattern happens too early, it’s too warm, and Main Lodge has rain.
Of course, I will watch the long-range daily now, as November is just about halfway through the 45-day Weather Trend Outlook Period.
Steve Taylor – the Mammoth Snowman
There will be a 5 PM update on the Weather later in the day on Sunday to see how the storm is coming along and whether there will still be a dusting of snow.
Mammoth Weather Forecast Data
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: Over the next week, expect a slow cool down, as shown below, with the blues moving over California. The cooler weather looks to be in the area for the next 10-14 days before there is a bit of a warm-up again. You can kiss the heat of Summer goodbye this week in the Southern Eastern Sierra.
*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.
45-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
Last Update from DWP Precipitation for Mammoth Pass & the Eastern Sierra
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*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.
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