Powder Forecast – Tuesday, March 4th, 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)
Tue 3/4 = 0”
Wed 3/5 = 1 – 2” (H20 = 0.10” – 0.15”)**3
Thu 3/6 = 10 – 14” (H20 = 1.00” – 1.35”)**3
Fri 3/7 = 2 – 3” (H20 = 0.15” – 0.25”)**3
Sat 3/8 = 0”
Sun 3/9 = 0”
Mon 3/10 = 0”
Tue 3/11 = 6 – 10”
Wed – Fri 3/12 – 3/14 = 24 – 36”
March Snowfall = 10”
March Forecast = 70 – 90”
Detailed 4-day Snowfall Forecast:
Wed 3/5 –Snowfall, heavy at times, changes to snow showers during the late afternoon and evening and continues overnight. Accumulations 10 – 14” by Thursday AM at Main, 15”+ up top.
Thu 3/6 – Snow showers continue at times during the day before tapering off overnight. Accumulations 2 – 3” by Friday AM at Main, 3”+ up top.
Fri 3/7 and Sat 3/8 – No snowfall expected both days.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) shows weak high pressure still positioned over the southern half of the state, with clouds out ahead of the weather system in the eastern Pacific spilling into Central California. Those clouds should continue to build through tonight as the storm approaches the coast.
The models move the low-pressure area and plume of clouds/moisture into Central California on Wednesday (image below), with a trailing upper-level low following its path into SoCal on Thursday. Even though it is not a particularly strong trough, it looks like it will phase with some subtropical moisture and become a good powder event.
Snowfall starts early Wednesday and increases through the morning and afternoon hours when it may be heavy at times (riders of the storm get out there!, winds don’t look super strong and Ch 22 may run). Snow changes to showers during the evening that should continue at times through Thursday afternoon.
Model QPF is generally in the 1.00-1.75” liquid range with the National Blend of Models the wettest (image below) and the others mostly in the 1.00”-1.35” range (images below). Snow levels will be around 6500-7000 feet Wednesday when the bulk of the snowfall occurs before snow levels fall to near or below 4000 feet by early Thursday. Thus, it will be Sierra cement-type snow on Wednesday, followed by a colder layer of a few inches overnight on Wednesday and Thursday.
The system exits eastward Thursday night and high pressure will then build into the state through Saturday (image below) resulting in a bluebird powder morning Friday and continued sunny weather Saturday. Temps should stay cold and winter-like Friday and warm to more typical early March ranges by Saturday and Sunday.
Long Range (Days 5+):
The longer-range guidance has now trended quite favorably. It appears that the storm door will remain open next week, and there is a very good chance for significant snowfall around mid-week. There is a chance it could then remain active through mid-month or slightly longer, although that part is still uncertain.
The ECM model moves the next upper-level trough into CA around next Monday (image below), while the GFS model is weaker and farther southward upon landfall. However, the GFS ensemble mean (two images below) matches up fairly closely with the ECM model in terms of both position and strength.
QPF for the storm with the operational models is in the 0.50”-0.75” range. The forecast follows the ECM EPS (image below), which shows a bit more and around 0.85”. That should equate to at least six inches of snowfall at Main and possibly up to 10”. The current timing is that most of the snow falls Monday overnight and into Tuesday.
The guidance quickly follows that storm with a potentially bigger storm around mid-week. The ECM EPS (image below) and the GFS ensemble (two images below) show a very deep trough developing along the West Coast and a strong diffluent jet stream into the Sierra. The ECM is slightly deeper than the GFS and has a bit more overwater trajectory with the longwave trough.
The storm appears to be a two to three foot event, and the ECM EPS generally agrees with around 2.5”-3.0” of liquid forecast (image below). It also looks like a colder storm, with snow levels in the 4-5000-foot range or even lower on the back end of the event. However, it is still more than a week out, and the details will change, but confidence is growing for a good dump.
The longer-range model output is slightly different, with both the GFS ensemble (image below) and the EPS showing a longwave trough along the West Coast. The GFS is more zonal into NorCal, while the ECM EPS has more troughing into CA with the jet stream farther southward. That is reflected in the QPF output with the ECM EPS showing above normal precipitation for that week (image below) while the GFS has only average (two images below).
Hopefully, the ECM EPS is right, as the ECM deterministic run from this morning matches up well and has around 7” liquid for the period. The snowfall estimate using the Kuchera method (two images below) is off the chart for the mountain, and around 5 feet of snowfall at the airport. While that is likely overdone, the message is clear, winter is not over yet, and many more powder days await. WG
