Powder Forecast – Tuesday, November 18th, 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 11/19 = ~ 1”
Thu 11/20 = ~1”
Fri 11/21 = 3 – 4” (H20 = 0.30” – 0.45”)**3
Sat 11/22 = 0 – 1”
Sun 11/23 = 0”
Mon 11/24 = 0”
Tue 11/25 = 0”
Wed – Fri 11/26 – 11/28 = 0”
November Snowfall = 19”
November Forecast = 25 – 30”
Detailed 4-day Snowfall Forecast:
Wed 11/19 –Slight chance for an afternoon flurry, otherwise dry. Snowfall develops late at night. Accumulation around 1” by Thursday AM.
Thu 11/20 – Mostly light snowfall during the day and into Thursday night. Accumulations 3– 4” by Friday AM at Main, up to 6” up Top.
Fri 11/21 – Snow showers decrease during the morning with just a chance for snow showers during the rest of the day. Little or no accumulations expected.
Sat 11/22 – No snowfall expected.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) this afternoon shows an area of low pressure just off the SoCal coast, with some clouds/snow showers wrapping around the counterclockwise circulation back into the eastern Sierra.
Snow showers should continue into this evening under this flow, then end tonight, with mostly dry weather returning tomorrow. The ECM model (image below) shows trace amounts of precipitation for the rest of today, while the GFS shows a bit more, which could add up to an inch of snowfall, but nothing significant.
The next weather system moves southward on Thursday (image below) and Friday, then becomes mostly stationary over northern Baja by Saturday (two images below). It will be a coastal hugger, and there will not be good jet stream forced upslope flow against the Sierra, and snowfall amounts appear light from the frontal passage. Snowfall begins early Thursday and continues at times into Thursday night before tapering off Friday morning. It should make opening day enjoyable.
The GFS model is the wetter model (image below), with around half an inch of liquid water; the latest ECMWF run shows about half that, and around a quarter inch (image below). The Forecast leans toward a blend of the ECM EPS (three images below), which shows about a third of an inch, and the GFS model, which shows a solid few inches of snowfall. Probably won’t be a difference maker in the long run, but every bit helps early in the season.
Long Range (Days 5+):
The longer-range guidance shows a less active pattern starting this weekend and lasting through most of next week or longer. The pattern may get somewhat active again during the first part of December, although current guidance is not favoring the big storm pattern that we need soon to develop a good base for powder skiing.
A weak high-pressure system will build into the state Sunday and persist for most of next week, bringing fair, dry, and seasonable weather. Temperatures should be cold enough at night for snowmaking. An inside slider-type weather system (image below) is forecast to move southward east of the state toward the end of next week, bringing slightly colder weather and some breezy winds; otherwise, dry weather continues into Thanksgiving weekend.
The longer-range guidance favors the development of a longwave trough across the interior West through the end of the month (image below) and into early December. Unless one of the systems moves far enough westward for a better over-water trajectory into the state during its passage, that is a predominantly dry/cool weather pattern.
The guidance suggests that it is possible with the ECM EPS (image below) showing about 0.75” for the period and more than six inches of snowfall. However, I would say that is not the favored outcome, and light snowfall amounts and colder temperatures are the better call at this point.
The fantasy range models suggest that the trough could briefly retrograde westward over the first week of December, increasing the chance of significant snowfall. The Forecast is showing above normal precipitation for the 7 days (image below), which would be around 2”+ liquid for that week. The control run shows a bottomless trough into CA around December 3rd (see two images below).
The guidance then shows average precipitation in the second week of December (image below), although there is a slight chance of a breakthrough of the westerlies. A lot will depend on the MJO; if it stalls in phase 7 during the mid part of December, Mammoth gets lots of snowfall. If it moves eastward into phase 8, it could be a dry month, with a deep/cold trough over the Midwest and East Coast and an anchoring high-pressure ridge along the West Coast. WG
