Powder Forecast – Tuesday, March 11th, 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 3/12 = 0 – 1”
Thu 3/13 = 18 – 24” (H20 = 2.00” – 2.50”)**3
Fri 3/14 = 6 – 8” (H20 = 0.40” – 0.50”)**3
Sat 3/15 = 6 – 9” (H20 = 0.40” – 0.60”)**3
Sun 3/16 = 0”
Mon 3/17 = 0 – 2”
Tue 3/18 = 6 – 10”
Wed – Fri 3/12 – 3/14 = 5 – 10”
March Snowfall = 25”
March Forecast = 70 – 85”
Detailed 4-day Snowfall Forecast:
Wed 3/12 – Dry during the morning, then snowfall starts in the afternoon and becomes heavy during the evening and overnight hours, decreasing toward dawn. Accumulations 18 – 24” at Main by Thursday AM, 24”+ up top.
Thu 3/13—Snow showers continue during the day before tapering off and briefly ending overnight. It’s very cold. Accumulations 6 – 8” at Main by Friday AM, 10”+ up top.
Fri 3/14 – Light to moderate snowfall develops during the morning and continues during the day, tapering off and ending at night. Accumulations 6 – 9” at Main by Saturday AM, 10”+ up top
Sat 3/15 – No snowfall expected.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) this afternoon shows a weather system positioned just off the SoCal coast and high pressure stretching across NorCal and into the interior West. A developing storm is also seen moving into the eastern Pacific with a band of clouds associated with the cold front and abundant open-cellular cumulus clouds behind the front with the upper-low.
The models move the deep upper-level trough onto the West Coast tomorrow afternoon (image below) and a strong southwest jet stream into the Sierra associated with a potent short-wave rounding the base of the trough. It will be strong enough for good spillover flow into the eastern side and far enough southward that Mammoth should see significant snowfall.
The initial snowfall associated with the cold front will not be super cold, and snow levels will be around 5500-6000 feet before decreasing overnight/Thursday morning to almost 3000 feet. That means the snow falling on late Wednesday and Thursday will be super fluffy, with snow-to-liquid ratios in the 15:1 range.
Model Quantitative Precipitation Forecasts (QPF) for the storm are generally over 2” liquid and up to close to 3” liquid. The GFS is the wettest (image below) with almost 3” liquid. The ECM (two images below) and NBM (three images below) have around 2” to 2.5”. The Canadian is forecasting just under 2” liquid. Still, it has 3” along the Sierra crest. Forecast follows closer to the GFS/NBM solutions with almost 3” for the event. Two feet seems like a good bet for the event at Main, with a chance for close to 30”.
Another short wave will quickly follow that storm on Friday (image below), with snow increasing during the morning hours, peaking in the afternoon, then decreasing during the evening and ending overnight. With the cold air in place, it will also be the fluffy, dry type of powder with high snow-to-liquid ratios. This time the snow will fall during operating hours and an opportunity for the riders of the storm.
Amounts don’t look super impressive with the GFS model not showing much at all in addition to the GFS ensemble (image below). The forecast follows the ECM (two images below) and ECM EPS (three images below) that are showing around 0.50” liquid and would result in around 6 – 9” of new snowfall and enough for continued powder conditions. Powder conditions should continue Saturday (probably when the top pops) under dry and partly cloudy skies.
Long Range (Days 5+):
The longer-range guidance has continued to trend drier for the last part of the month, with a dry period now looking probable to start the last week of the month. Storms could come back in late March or early April, which is the back end of the powder season, which comes with no guarantees. It is certainly possible that the storm this week could be the last big storm of the season.
The next chance for snowfall will be late Sunday and/or Monday next week when the guidance advertises the passage of another short-wave trough (image below). It does not look as strong as the storm this week and appears to be a rather typical late-winter system. The ECM EPS (two images below) is showing around 0.50” liquid, and that could be enough for six inches at Main.
The longer-range GFS ensemble moves a couple of systems into the northern half of the state toward the end of next week (images below). The ECM EPS is not as deep as the GFS with the short-wave troughs and keeps them farther northward. That model (bottom image) is only showing light amounts around a quarter inch liquid for the period, probably not enough for powder conditions. The GFS ensemble has twice as much and would probably be enough for low-end powder.
The models now favor the longwave trough to move into the central US during the last part of the month (image below). The ECM moved the trough farther eastward quickly that week while the GFS held it back further westward. There is a chance a weak system could drop into CA from the north as the trough shifts eastward, but the guidance is not too bullish about anything other than very light amounts of precipitation (two images below) for that period.
The super long-range ECM EPS shows the longwave trough reforming along the West Coast during the last part of the month and early April (image below). Nothing is big yet, with the model just showing average precipitation for the period. The GFS extended is similar and keeps chances ongoing into mid-April. Let’s hope it happens. WG
