Powder Forecast – Tuesday, December 23rd, 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 12/24 = 9 – 12” (H20 = 1.30” – 1.60”) **4
Thu 12/25 = 28 – 34” (H20 = 3.50” – 4.00”) **4
Fri 12/26 = 24 – 30” (H20 = 2.50” – 3.00”) **3
Sat 12/27 = 2 – 4” (H20 = 0.25” – 0.35”) **3
Sun 12/28 = 0”
Mon 12/29 = 0”
Tue 12/30 = 0”
Wed – Fri 12/31 – 1/2 = 0”
December Snowfall = 0”
December Forecast = 55 – 70”
Detailed 4-day Snowfall Forecast:
Wed 12/24 – Heavy snowfall continues during the day, tapering off in intensity overnight. Strong winds. Snow levels around ~8000 or slightly higher in the morning, then lower to 7500 by late AM, then down to 6K overnight. Accumulation at Main 30-36” by Thursday AM, 40”+ up Top.
Thu 12/25 – Snow, heavy at times, redevelops during the day and continues overnight. Accumulation at Main 24-30” by Friday AM, up to 36” at the Top.
Fri 12/26 – Snowfall tapers off during the day and ends by evening. Accumulation at Main: 2-4” by Saturday AM, up to 6” at the Top.
Sat 12/27 – No snowfall expected.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) shows clouds streaming into California ahead of a developing mid-latitude bomb cyclone now off the SoCal coast. It will move northwestward overnight and into Wednesday, and should move into southern Oregon early Christmas Eve morning.
The short wave that is part of the larger longwave trough (image below) will drive a strong cold front eastward into the Sierra early Christmas Eve Heavy snowfall should develop overnight and continue for most of the day, before tapering off a bit but continuing Christmas Eve night and into Christmas The ECMWF is forecasting around an inch (two images below) liquid by 6 AM. The GFS is forecasting closer to 1.5” (three images below) for a quick start.
ECWF forecast 700-mb temperatures (two images below) show -1°C to -2°C temps to start the event and suggests snow levels around 8000 feet or even slightly higher Dynamic cooling with the front should then lower snow levels to below 7500 by late morning with snow levels not remaining an issue for the rest of the event Thus, there could be some rain at Eagle that should change to snow by mid-morning.
This event has a few things that will be good for snowfall
- Snow levels are low enough for snowfall on most of the mountain for the entire event
- The trough has a good moisture tap with a plume of closer to 1” or larger for the entire event
- It is not a fast mover, with three waves of snowfall that will add up
Model QPF for Christmas Eve is impressive with the GFS model higher (image below) at around 3.5” liquid and the ECM showing about 3” liquid (two images below) Forecast follows the larger values as Mammoth is in the perfect spot in this set-up with southwest flow perfectly aligned up the San Joaquin River channel into Mammoth Expecting at least a couple feet at Main during the day and overnight.
The ECM model moves the parent low toward the coast on Christmas (image below), and that is when the second round of snowfall will start. Snow levels will be around 5500-6000 feet, but it should still be Sierra cement-type snowfall.
The upper low will slowly move southward along the coast into Saturday (image below. One last round of moderate to heavy snowfall is forecast for Christmas night and into Friday morning before dry weather returns Friday night and Saturday. Snow levels will be down to 4500-5000 feet, so that snowfall may be a touch lighter, but still on the heavy, wet side.
The ECM QPF model (two images below) shows around 2” of liquid, and the GFS is larger again (three images below), at around 3.5”. The forecast uses a blend of the two, and another 2 feet of snowfall is likely at Main by Friday morning.
Total QPF for the event by the models is substantial with the ECM the lowest (image below) at around 6” and both the GFS (two images below) and NBM (three images below) showing around 9-10” liquid The ECM EPS has almost 8” and the forecast leans toward that for the low end and the GFS/NBM on the high end Good shot for 5 feet at Main for the event and 6-7 feet up Top.
Long Range (Days 5+):
The longer-range guidance indicates a return to dry weather for the rest of 2025, with the next chance of snowfall sometime in the first week of 2026. The super long-range guidance is still somewhat active in the first part of January, but has trended in the wrong direction since the last post.
The ECM model moves a strong ridge of high pressure into the West Coast over the weekend and into next week (image below), and mostly holds it there for the rest of the week. That would mean dry weather and potentially seasonably mild temperatures again.
The ECM model doesn’t end the dry weather until late the first weekend of 2026, and into the following week when it moves a strong short-wave trough into California (image below). That solution is somewhat supported by the ECM EPS (two images below), which has a trough in the northwest flow.
The differences are starker with the QPF, with the 12z ECM run showing about 2 inches of liquid (image below) and the ECM EPS about 1 inch (two images below). Even an inch would be great, as it would be a cold-type storm with drier powder on Top of what will be a good base. Fingers crossed.
The fantasy range models are less bullish about a good storm pattern beyond the second week of January, with mostly average precipitation expected for the period, or slightly below normal around mid-month (images below), particularly after January 12th. With the SPV forecast to remain strong through January, I think our chances of a powder day are pretty good.
