Powder Forecast – Friday, March 7th, 2025
Ted Schlaepfer CCM —- Mammoth Mountain WeatherGuy
Snowfall forecasts are valid at the Sesame snow course (Main Lodge) for the prior 24 hours as reported in the 6-7 AM morning snow report.
**Snowfall forecast confidence ranges from very low (1) to very high (5)
Sat 3/8 = 0”
Sun 3/9 = 0”
Mon 3/10 = 0”
Tue 3/11 = 0 – 2”
Wed 3/12 = 0”
Thu 3/13 = 18 – 22”
Fri 3/14 = 6 – 10”
Sat – Mon 3/15 – 3/17 = 5 – 10”
March Snowfall = 25”
March Forecast = 70 – 85”
Detailed 4-day Snowfall Forecast:
Sat 3/8 through Mon 3/10 – No snowfall expected all days.
Tue 3/11 – Dry during the morning, then a chance for light snow showers during the afternoon and evening. Maybe an inch or two accumulation.
Forecast Summary:
Short Term (Days 1 – 4):
The infrared satellite image (below) this afternoon shows that the weather system that produced the snowfall over the past two days has moved into Arizona. High pressure off the coast is currently building eastward into the state.
Models hold the high-pressure ridge over CA and Mammoth through the weekend (image below) and into Monday. That means sunny weather and generally seasonable temperatures with freezing levels around 10,000 feet, meaning temps should remain in the 20s up top and low to mid-30s at McCoy.
Models are now projecting the next weather system on Tuesday (image below) to move too far southward into SoCal for any significant snowfall in Mammoth. The guidance was farther northward with this low in the last post and is an excellent example of how far off the models can be in the medium to long time frames.
The models are now saying only very light amounts may fall. The GFS is the wettest (image below) at about two-tenths, the ECM shows half that (two images below), and the National Blend of Models (three images below) shows basically nothing. The forecast is calling for just a chance of light snow showers Tuesday PM/evening, not enough for powder conditions.
Long Range (Days 5+):
The longer-range guidance still looks good in the extended time frame but not as good as in the last post. A bigger storm next week is still highly likely, and any storminess after that looks more questionable now through the end of the month.
All of the guidance (ECM EPS below) shows the development of a very deep full-latitude trough along the West Coast on Wednesday next week. It has a strong divergent jet stream into CA and the Sierra that would result in a period of heavy snowfall and good spillover into the eastern side.
It is still 5-6 days out, and the details have changed over the past few model runs, with the general trend being weaker. It still looks quite cold on the back end of the storm, with snow levels getting down below 3000 feet. That means the top layer of powder will be the dry type. The current timing is snowfall starting Wednesday PM. Most of it falls overnight into Thursday, with continued snow showers on Thursday.
The ECM EPS QPF for the storm is around 2” liquid (image below), and the GFS ensemble is similar (two images below). Snow ratios will probably start out 10 to 1 before getting higher, and around 12-15 inches of snowfall to 1-inch liquid on Thursday when the coldest air arrives. I’m still hoping for two to three feet of snowfall at Main and three-plus feet up top.
The next storm system may arrive the following Monday per the ECM EPS (image below), with another trough moving into NorCal. Mammoth would be on the southern boundary for good precipitation, as this storm would favor Tahoe. That is reflected in the QPF from the ECM EPS (image below) that has almost an inch liquid for Mammoth and the focus for heaviest precipitation farther northward. Thus, hopefully, at least six inches could happen or slightly more, I have low confidence this far out.
Beyond that, the ECM EPS moves the jet stream northward while the GFS ensemble (image below) is farther southward and moves a weak wave into the state toward the end of the week. So, there is a chance for more snowfall, but it might not add up to much if it happens. After that chance, the latest ECM super long range favors dry weather for the last part of March (image below). The time to get the powder days is now. WG
