Powder Forecast – Tuesday December 27th, 2022
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 12/28 = 17 – 20” (H20 = 2.50” – 2.75”) **4
Thu 12/29 = 1 – 2” (H20 = 0.15” – 0.25”) **4
Fri 12/30 = 6 – 8” (H20 = 0.65” – 0.85”) **3
Sat 12/31 = 10 – 15” (H20 = 1.75” – 2.25”) **3
Sun 1/1 = 22– 28” (H20 = 2.75” – 3.25”) **3
Mon 1/2 = 0”
Tue 1/3 = 3 – 6”
Wed – Fri 1/4 – 1/6 = 30 – 60”
December Snowfall = 84”
December Forecast = 115 – 125”
Detailed 4-day Snowfall Forecast
Wed 12/28 – No snowfall expected during operations with light snowfall developing late at night. Accumulations 1 – 2” by Thursday AM
Thu 12/29 – Light snow during the morning, dry during the afternoon, followed by increasing snowfall overnight. Accumulations 6 – 8” by Friday AM.
Fri 12/30 – Snow or rain (lower part of mountain) during the day and overnight. Accumulations 10 – 15” by Saturday AM, ~20” up top
Sat 12/31 – Heavy snow during the day and into the early evening, then snowfall ends overnight. Accumulations 22 – 28” by Sunday AM, up to 36” up top
Short Term (Days 1 – 4):
The current infrared satellite image (below) shows a large storm system moving through Central California with heavy snowfall today in Mammoth. The system contains an Atmospheric River (AR) and snow levels have been hovering around 7500 feet.
The ECM model (image below) is forecasting about 2.5” more liquid from this morning until the snowfall stops overnight and up to another 20” of new snow at Main is possible to go with the 7” from this morning.
Tomorrow is expected to be a dry day after the snow stops during the early morning with partly cloudy skies during the afternoon. Clouds increase tomorrow night leading to light snowfall late at night and during the day Thursday.
That snowfall is moisture moving into the state out ahead of the next juicy storm system forecast to move across the NorCal on Friday (image below). The strong warm front (two images below) will increase orographic precipitation in the Sierra Friday with snowfall increasing on the mountain during the day and remaining steady into the night.
The system will contain a weak AR at Mammoth’s latitude (image below), but it will be long-lasting (purple box) and that will push it into moderate categories. The sub-tropical nature of the air mass will also push snow levels upward with levels near 8500-9000 feet by Friday afternoon and night. That means it could rain at Canyon with a slight chance for a period of rain at Main.
The upper-level trough will then swing through the southern part of the state on New Year’s Eve (image below) and snowfall will become heavy in Mammoth during the day before decreasing late evening and ending overnight. It looks like another two feet could fall at Main by Sunday AM or New Year’s Day.
Long Range (Days 5+)
The longer-range guidance is saying that these first couple of storms are the first part of a significant storm cycle that will continue through at least next week. Storm cycles like these are key to a long-lasting season as the seasons when they don’t occur usually end up with a Memorial Day closing. This cycle will also put a dent into the ongoing drought.
The ECM model moves the next short-wave trough in the zonal flow off the Pacific into CA around Monday next week (image below) after a dry New Year’s Day. Light to moderate snowfall is expected from this one with maybe 6” at Main by Tuesday AM.
The longer-range guidance is then suggesting the biggest storm of the series will impact Mammoth around the middle part of next week. The ECM develops a strong and long-fetched southwest jet stream (image below) with the main core of the jet directly into the Mammoth area.
It then moves the deep upper trough through the state on Thursday (image below) before exiting on Friday. This is a perfect set-up for a major blizzard in the Sierra with cold upper-level support and a long fetch of moisture to wring out snowfall. Even though it is a week out, confidence is fairly high for a big storm as the ECM ensemble mean (two images below) matches up nicely with the deterministic run.
The ECM model is showing very heavy amounts for next Wednesday (image below) in the 5” liquid range. This could be one of those rare situations when 4-5 feet of snowfall occurs in about a 24-36 hour period.
Overall, the models for the next 10 days are extremely wet with the ECM (image below) and GFS (two images below) both showing around 20” liquid. The 15-day GFS has about 25” liquid (three images below) and that amount is comparable to the amounts that occurred in January 2017. So the mountain should be quite buried in snowfall by the end of next week.
The fantasy range guidance is suggesting a break for a few days at the end of the first week of January (image below) and into the second week (two images below). It is only a weak ridge, and the GFS operational model keeps more storms moving into Mammoth for the entire period. So there is a chance it will keep on snowing. WG