Powder Forecast – Friday January 3rd, 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 1/4 = 3 – 4” (H20 = 0.25” – 0.45”) **3
Sun 1/5 = 0”
Mon 1/6 = 0”
Tue 1/7 = 0 – 1”
Wed 1/8 = 0 – 2”
Thu 1/9 = 0”
Fri 1/10 = 0”
Sat – Mon 1/11 – 1/13 = 0”
January Snowfall = 0”
January Forecast = 45 – 60”
Detailed 4-day Snowfall Forecast:
Sat 1/4 through Monday 1/6– No snowfall expected all days except for a slight chance of light snowfall late Monday night.
Tue 1/7 – A slight chance of light snowfall during the day and into the evening. Accumulations 0 – 2”.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) this afternoon shows a weather system moving into the West Coast with clouds and rain. The associated cold front will weaken as it moves through Central California and toward the Southern Sierra this afternoon and evening with Mammoth only getting the passage of the tail end of front.
Model QPF still varies quite a bit for such a short-term forecast with the ECM model still the driest at around a couple tenths (image below), but certainly more versus the last post. The GFS is one of the wetter models (two images below) and has about a 0.40”+ while the NBM is on the wet side too at around 0.50” (three images below). The Canadian is between them all again at around a quarter inch (bottom image).
Forecast takes the middle ground with about 0.35” liquid and hopefully up to 3” or so inches of snowfall and a hefty few inches up top. There should be enough by Saturday morning for low-end powder turns, especially in the powder fields up top. Best case scenario is the GFS snowfall using the Kuchera method that has about 6” of snow (image below). Snow levels will be around 5000 feet.
The rest of the weekend and into early next week should be dry with weak high pressure building over the state. The next chance for snowfall will be associated with the passage of a back-door upper-level low moving westward toward the coast Monday night and Tuesday (image below). If the low is deep enough it can often produce moist upslope flow on the east side of the Sierra, but the trajectory and strength need to be just right.
The latest GFS says it will be deep enough to produce a couple/few inches of snowfall, primarily on Tuesday morning with almost a quarter inch of liquid forecast (image below). The ECM is not as bullish with only trace amounts of liquid/snow (two images below). Forecast is calling for just a chance of snowfall at this point. Very often, these events are just dust on crust, with the main affect being strong easterly winds, primarily top half of the mountain.
Long Range (Days 5+):
The longer-range guidance is favoring dry weather to continue through mid-January or longer. There is still no exact sign of when this upcoming dry spell will come to an end, best guess right now is just after mid-month with storminess picking up over the last 7 to 10 days of the month.
The longer-range guidance has high pressure building over the state over the latter part of next week for dry and warmer weather. Freezing levels could approach 12K by Friday resulting in temps into the 30s up top and even spring conditions on the Ch. 25/Ch. 9 side of the mountain during the late AM/early PM timeframe.
The GFS ensemble is then favoring another inside slider type weather system to move southward through Nevada over the latter part of the following weekend (image below). That would mean colder temps, a slight chance for light snowfall, and also an increase in northeast winds. High pressure would likely then rebuild early over the next week (Jan 13th).
This pattern may then last for most of that week with the fantasy range guidance suggesting that the longwave trough over the middle/eastern US may retrograde westward by the end of the week/weekend. The first trough (image below) may then move far enough southward for some snowfall in Mammoth. If this pattern evolves, it will support cold-type storms originating from higher latitudes that produce cold, dry powder followed by storms coming off the Pacific Ocean that have more moisture.
This does line up with the MJO forecast that moves it into phase 2/3 with some of the ensemble members favoring a strong signal (image below). MJO composites (images below) favor cold temperatures and not a lot of liquid precipitation (colder type storms) in phase 2 over Central California. Phase 3 favors only slightly below normal temperatures, but above normal precipitation and possibly big storm(s) or a storm cycle. That would happen over the last 7-10 days of the month. WG
