Powder Forecast – Tuesday, December 30th, 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)
Wed 12/31 = 0”
Thu 1/1 = 1 – 2” (H20 = 0.45” – 0.55”) **2
Fri 1/2 = 3 – 4” (H20 = 0.50” – 0.65”) **3
Sat 1/3 = 1 – 2” (H20 = 0.10” – 0.20”) **3
Sun 1/4 = 12 – 16” (H20 = 1.50” – 1.75”) **2
Mon 1/5 = 5 – 10”
Tue 1/6 = 4 – 8”
Wed – Fri 1/7 – 1/9 = 5 – 10”
December Snowfall = 63”
December Forecast = 63”
Detailed 4-day Snowfall Forecast:
Sat 12/27 through Tue 12/30 – No snowfall expected all days.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) this afternoon shows high pressure centered over Oregon and clouds streaming northward into CA from the ocean just west of Baja. The low-pressure area situated on the western edge of the clouds will slowly move northeastward on Wednesday and Thursday, pulling that subtropical moisture northward with it, resulting in snow/rain for the mountain.
The models suggest that maybe an inch of liquid precipitation will fall with the GFS, the wettest (image below), at well over an inch, the NBM slightly drier (two images below) at about an inch, and the ECM the outlier at around 0.75” (three images below). The forecast leans toward the NBM and about an inch of liquid.
The main issue will be snow levels as the moisture source is subtropical. Snow levels may start around 9000 feet or slightly higher on Wednesday afternoon, when precipitation begins, then lower to around 8000-8500 feet overnight into Thursday morning, as the bulk of the precipitation moves through. So, it will be mostly wet Sierra cement snow at Main, a mix of rain and snow at Canyon, and mostly rain or a mix until the end at Eagle, when it may briefly turn all snow.
The models move a stronger, more traditional storm into the Sierra early Saturday (image below), and it should produce good snowfall across the entire mountain. That is followed by another one (two images below) on early Sunday. Both are coming out of the southwest with ample moisture. They are not cold storms with snow levels around 6000-7000 feet for the event,t and should be more Sierra cement-based type snowfall.
The ECM model (image below) is showing about 2” of liquid for the storms, and the GFS (two images below) has a bit more. Both models are saying at least a foot of snowfall for the first one Saturday and possibly up to 20 inches (three images below) by Sunday night. Most of the snowfall will occuron Saturday during the day for those riding the storm.
Long Range (Days 5+):
The longer-range guidance suggests the active pattern will continue into the following week before the pattern turns dry through mid-month, at least one model says. If it does go dry, snowfall could return by the end of January, and overall, that outlook has not changed too much since the last post.
The guidance is in agreement that another short-wave trough will move into CA on Monday (image below), bringing another round of moderate to heavy snowfall. The ECM model (two images below) and the GFS (three images below) both show over an inch of liquid from the storm, or possibly another foot.
The 12z run of the ECM brings another trough southward around mid-week (image below), but the ECM EPS is showing a much weaker pattern (two images below). The QPF is still over an inch (three images below), showing significant station/spread. Let’s hope the trend is toward wetter solutions.
That is because a dry pattern will probably emerge in the 11-15 day time period. The models disagree on the pattern, except that it will probably be mostly dry or dry. The ECM EPS has a flat ridge over the state (image below) that would be dry (two images below) and seasonable. The GFS ensemble has the ridge offshore and a trough over the interior West (three images below). That is a colder pattern, but mainly dry, with inside slider-type storms, although there is a chance for one to move farther southward over the ocean.
The fantasy range ECM EPS still shows a dry period starting/continuing through mid-month (image below), before possibly returning to snowfall in the last part of January (image below). The GFS extended is different, though, with wet weather continuing through mid-month (three images below) and drier weather for the latter part. Either way, there are a lot of potential powder days next month. WG
