Powder Forecast – Friday, December 5th, 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 12/6 = 0”
Sun 12/7 = 0”
Mon 12/8 = 0”
Tue 12/9 = 0”
Wed 12/10 = 0”
Thu 12/11 = 0”
Fri 12/12 = 0”
Sat – Mon 12/13 – 12/15 = 0”
December Snowfall = 0”
December Forecast = 30 – 50”
Detailed 4-day Snowfall Forecast:
Sat 12/6 through Tue 12/9 – No snowfall expected all days.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) this afternoon shows high pressure parked off the CA coast and storm systems riding up and over the ridge. The ridge will remain mostly in place through the weekend and into next week for continued fair/dry weather and seasonably mild temperatures.
Long Range (Days 5+):
The longer-range guidance still favors a mostly dry weather pattern through mid-month. Any hints of possible positive changes have been pushed back to Christmas week and into the New Year’s time frame.
High pressure will slide eastward over the state toward the middle/end of next week (image below), and the ECMWF suggests it could get relatively strong for a period of even milder weather. While it would not melt snow, it would hamper snowmaking. This pattern may now hold through the following weekend.
The latest ECM model shows a deep trough moving into the state around the middle of the following week (image below), producing decent precipitation (two images below) that would amount to over a foot of snowfall.
Unfortunately, that solution is not supported by the ensemble means of both the ECM (image below) and GFS (two images below), which both show a ridge either just off CA or over the state, respectively, for continued dry weather.
Both models do favor weak zonal flow at the very back end of the period, with most of the precipitation well north of Mammoth (images below). While there could be some snowfall, it certainly isn’t the big snowfall pattern we need right now.
Taking a look at what is happening in the tropics with the MJO, it has now moved into phase 8, a little faster/farther eastward than forecast a week ago. Both models halt the eastward progression of the signal and reduce its amplitude toward the unit circle over the next week or so. The GEFS (image below) reamplifies it in phase 7 just after mid-month, before moving it back into phase 8, while the ECM (two images below) generally stalls it in phase 8 and keeps it weak.
With the stratospheric polar index forecast to remain neutral through the third week of December (image below), this is a dry pattern for CA, even if the MJO regains amplitude per the GFS. The best-case scenario for increased precipitation in CA would be for the SPV to strengthen and the MJO to remain weak, or for the MJO to move eastward into phases 1, 2, and 3, with the SPV remaining neutral/weak.
The fantasy range guidance indicates that snowfall will increase in the latter part of the month. The GFS extended (image below) is showing around 4” of liquid for the last part of December, and the latest control run (two images below) is showing a lot more.
The ECM EPS extended forecast is not showing as much as the GFS (image below), and its control run is almost arid (two images below). It is a wait-and-see situation at this point, and we hope that the variables align to end this dry spell soon. WG
