Powder Forecast – Tuesday January 21st, 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 1/22 = 0”
Thu 1/23 = 0”
Fri 1/24 = 0”
Sat 1/25 = 0 – 1”
Sun 1/26 = 1 – 5”
Mon 1/27 = 0 – 1”
Tue 1/28 = 0”
Wed – Fri 1/29 – 1/31 = 0”
January Snowfall = 1”
January Forecast = 2 – 5”
Detailed 4-day Snowfall Forecast:
Wed 1/22 through Friday 1/24– No snowfall expected all days except for a chance for light snow late Friday night.
Sat 1/25– Light to moderate snowfall is possible during the day with lingering snow showers possible into Sunday, quite cold. Accumulations by Sunday AM 1 – 5” at Main/Top.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) this afternoon shows a weak low-pressure system positioned well off the CA coast and high pressure just off the PacNW. A dry cold front is moving southward across the Interior West. This pattern will remain mostly unchanged through Friday for continued fair weather and mild January temperatures.
Dynamical models are then favoring a pattern change over the upcoming weekend with a deepening high-latitude upper-level trough diving southward into CA from western Canada on Saturday (image below) and then cutting off from the jet stream on Sunday over SoCal (two images below).
Weather systems moving into the state from that direction usually don’t have a good moisture source to produce significant precipitation or snowfall and the current guidance is in agreement. Nonetheless, light to moderate snowfall may start late Friday night and continue at times through Sunday. However, since it is a cut-off low, it’s exact position, strength and track will be key to how much snowfall occurs at Mammoth and the models currently don’t have a handle on that situation.
The ECM model is the wettest (image below) at around 0.35” and the Canadian the driest at under a tenth of an inch (two images below). The GFS also only shows light amounts around a tenth of an inch (three images below). So that would mean about an inch snowfall at the lower end to around 4-5” on the upper end per the ECM solution.
Current forecast follows the ECM EPS (image below) that has around 0.25-0.35” liquid, but also takes into account the drier GFS ensemble (two images below). The storm will be quite cold with snow levels around 4000 feet or lower and snow ratios with any snowfall will be high and in the 15-20”:1” range. However, it is still questionable whether enough of this drier powder snowfall will fall for low-end powder conditions or will it end up mostly dust on crust. Fingers crossed.
Long Range (Days 5+):
The longer-range guidance is still favoring mostly dry weather to continue through early February now. There is a slight chance for a weak storm during early February, otherwise best guess right now will be second week of February.
High pressure builds back into the state early next week and holds mostly in place just off the coast for the rest of the month as the cut-off slow slowly moves eastward through the SouthWest (image below), That will result in dry weather and seasonable temperatures.
The pattern for the first part of February does favor the high-pressure ridge to slowly weaken and move westward during the week as troughing develops over the PacNW and Britich Columbia (image below). The jet stream has a west-northwest orientation and is generally too far northward for any big storms to move southward into CA, but there is a chance a weak storm could drift southward into CA with a more northwest oriented jet. Regardless, dry weather will probably continue under continued seasonable or only slightly below normal temperatures.
The fantasy range guidance is favoring a more typical La Nina pattern developing during February and early March with the longwave trough centered over the West instead of the center of the US. The longwave trough may be far enough westward at times for storms to have enough over-water trajectory to produce at least moderate snowfall in Mammoth, hopefully heavy snowfall.
The GFS is more bullish on this scenario with above normal precipitation during the second week of February (image below) with the ECM not as bullish (two images below), but still having average precipitation. Unfortunately, the ECM model has shifted drier for February overall and is suggesting another below normal month. Fingers not crossed for that scenario. WG
