Powder Forecast – Friday, November 28th, 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 11/29 = 0”
Sun 11/30 = 0”
Mon 12/1 = 0”
Tue 12/2 = 0”
Wed 12/2 = 0”
Thu 12/3 = 0 – 2”
Fri 12/4 = 0”
Sat – Mon 12/5 – 12/7 = 0 – 2”
November Snowfall = 24”
November Forecast = 24”
Detailed 4-day Snowfall Forecast:
Sat 11/29 through Tue 12/2 – No snowfall expected all days.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) this afternoon shows high pressure over the state and a weak low-pressure system moving southward into the Great Basin east of Mammoth. The low off the CA coast will dip southward and become quasi-stationary off the SoCal coast by Sunday.
The other one off the PacNW will dip southward on Sunday (image below), a bit farther westward through the Great Basin as an inside slider. That should produce some breezy to gusty northerly winds during the day on Sunday, along with continued dry weather. The dry weather will continue Monday and Tuesday as weak high pressure briefly builds back into the region.
Long Range (Days 5+):
The longer-range guidance is still favoring a mostly dry weather pattern through the first week of December. The positive changes hoped for in the last post are not looking as promising now as what was expected. Both in the tropics and poles have changed since the last post.
The medium-range guidance favors another inside slider-type system around Wednesday next week (image below), and this one may retrograde further westward as it slides southward. It may be strong enough to produce a period of light snowfall on Wednesday that could add up to an inch or two.
The models cut the system off from the jet off the SoCal coast where it will linger through the end of the week and into the following weekend High pressure will build into CA north of the low and dry weather will continue/return for Mammoth through the end of the week before there is a slight chance for snowfall when the weakened low moves ashore over the weekend.
Since the last post, the MJO forecast has changed. The models are now faster moving the signal eastward through phase 7 and into phase 8 with the ECM (image below) and GEFS (two images below) fairly similar through about December 6-7th The GEFS now weakens the MJO signal toward the unit circle fairly quickly during the second week of December and keeps it generally weak for the rest of the month The ECM is not quite as fast with the degradation of MJO, but does eventually weaken it too and inside the unit circle by the last week of the month.
The other change is that the Stratospheric Polar Vortex (SPV) (image below) is forecast to only reach strong ranges briefly now before decreasing in strength back to neutral ranges by mid-month (per the Ensemble mean) where it may remain for the rest of December Thus, the potential tropical/polar teleconnection response (two images below) cited from the 2019 study and discussed in the last post may end up being image (f), and not (h), if the MJO signal remains coherent,
That is what is generally shown in the long-range guidance for the start of the second week of December (image below), with a weak trough in the eastern Pacific, a high-pressure ridge centered in eastern Alaska/B. Columbia, and a downstream trough in the Great Lakes/East Coast.
The pattern type (f) would allow for weak breakthroughs of the westerlies at times, and the GFS ensemble has one toward the end of the second week (image below). However, the ECM EPS does not (two images below) and keeps the ridge in place along the West Coast and the trough deeper in the East.
That drier pattern by the ECM EPS is shown in the 5-day precipitation anomaly forecast (image below) that shows slightly below normal precipitation The GFS ensemble (two images below) is a bit wetter with average precipitation for that period So, there is a chance for light to moderate snowfall late that week/following weekend Total ECM EPS precipitation for the 15 day period is about half an inch (three images below).
The ECM EPS and GFS extended both favor mostly dry weather during the third week (Dec 14-21) with the GFS mostly dry for the last part of the month and the ECM only slightly wetter, but still mainly on the dry side The 32-day forecast from the ECM EPS (image below) that covers all of December is showing below normal precipitation for the entire Sierra range and northern 2/3 of CA It shows about a 2” liquid deficit for the month at Mammoth Average December snowfall is around 60-65”, so that is suggesting a 35-40” month WG.
