Powder Forecast – Tuesday January 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)
Wed 1/29 = 0”
Thu 1/30 = 0”
Fri 1/31 = 0”
Sat 2/1 = 0 – 1”
Sun 2/2 = 1 – 2”
Mon 2/3 = 0”
Tue 2/4 = 2 – 4”
Wed – Fri 2/5 – 2/7 = 20 – 30”
January Snowfall = 10”
January Forecast = 10”
Detailed 4-day Snowfall Forecast:
Wed 1/29 and Thu 1/30– No snowfall expected both days
Fri 1/31– Dry during the day, then light snowfall develops overnight. Accumulations 0 – 1” at Main by Sunday AM and ~1” up top
Sat 2/1– Light snowfall during the day, ending evening or night. Rain lower mountain below 8500 feet. Accumulations 1 – 2” at Main by Sunday AM and ~3” up top
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) this afternoon shows the weather system that produced the snowfall over the weekend now positioned in western Arizona. High pressure has built into the PacNW and Mammoth is in between the two features resulting in fair weather and seasonably cold temperatures.
The high-pressure ridge will build southward through Thursday as the low pressure system slowly moves eastward through the SouthWest before a low pressure trough moves into the PacNW on Friday (image below). It will then move through central/northern CA on Friday night and Saturday producing light snowfall in Mammoth from the warm front Friday late night and then the tail end of the cold front Saturday.
Amounts with the storm appear to be light and mostly in the third of an inch range per the ECM (image below), quarter inch per GFS (two images below) and a tenth or so from the National Blend of Models (three images below). It looks like maybe an inch may fall by Saturday morning and then a couple inches during the day before ending Saturday night. Snow levels will be rather high and around 8500-9000 feet during the day Saturday, so there is a good chance for rain on the lower part of the mountain.
Long Range (Days 5+):
The longer-range guidance continues to trend more favorably and is now suggesting a good chance for a moderate to strong storm by the end of the first week of the month. That could be followed by additional chances through mid-month or longer as the big picture weather pattern shifts away from the dry pattern for the West Coast.
The jet stream shifts northward Sunday and into Monday, but the upper-level longwave trough is expected to shift westward and combine with another trough moving into the eastern Pacific. The end result is increased west/southwest flow into CA through mid-week with an embedded Atmospheric River increasing precipitation across NorCal dramatically.
The models eventually shift the jet stream southward into central CA by mid-week with the GFS model (image below) keeping the southwest flow into CA longer versus the ECM model (two images below) that shifts the trough eastward and shuts off the moisture faster. Both deterministic runs match their respective ensemble mean solutions (GEFS three images below) thus producing increased uncertainty with the forecast.
Model QPF varies significantly with the GFS model the wettest at around 6-7” liquid and the Canadian only slightly drier (two images below). The ECM solution (three images below) is showing about half the GFS amounts at around 3” liquid. Thus, snowfall amounts could range from as little as a couple feet per the ECM model to around 5 feet per the GFS.
Interestingly, the ensemble mean QPF from the ECM EPS and GFS ensemble are fairly close with both models (images below) showing about 2.5-3.5” liquid for the period with the GFS only slightly wetter. Overall, it looks like a good shot for a couple feet next week with most of the snow falling on Tuesday and Wednesday and lingering snow into Thursday. There will likely be a storm riding day or three next week too.
The fantasy range guidance differs slightly with the GFS ensemble having a more favorable solution for more powder days versus the ECM. The GFS (image below) ensemble has the longwave trough anchored across the West and far enough westward from low pressure systems to drop southward into CA from the Gulf of Alaska. The ECM model has the trough shifted farther eastward that would support inside sliders.
However, that model does shift the trough back westward at the end of the period while the GFS ensemble shifts the trough even farther westward that would allow more over-water trajectory with any incoming storms. That is what the CFS model is likely picking up on as it continues to forecast a good February (image below) with above normal precipitation in Mammoth by 2”+ liquid (normal is around 6”). At 10” to 1” ratios, that would be an 80” month, I’ll take it. WG
