Powder Forecast – Friday, November 22nd, 2024
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.
Sesame Snow Course
**Snowfall forecast confidence ranges from very low (1) to very high (5)
Sat 11/23 = 8 – 10” (H20 = 1.25” – 1.50”)**4
Sun 11/24 = 10– 12” (H20 = 1.00” – 1.25”)**3
Mon 11/25 = 0”
Tue 11/26 = 13– 17” (H20 = 1.25” – 1.50”)**2
Wed 11/27 = 12 – 15” (H20 = 1.50” – 2.00”)**2
Thu 11/28 = 0”
Fri 11/29 = 0”
Sat – Mon 11/30 – 12/2 = 0”
November Snowfall = 14”
November Forecast = 60 – 80”
Detailed 4-day Snowfall Forecast:
Sat 11/23 – Heavy snow during the morning decreases to moderate snowfall by the afternoon and evening before tapering off overnight. Accumulations 10 – 12” by Sunday AM at Main Lodge, up to 15” up top
Sun 11/24 – A few flurries are possible during the morning, then dry.
Mon 11/25 – Dry during the morning, then snowfall likely develops during the afternoon and continues overnight. Accumulations 13 – 17” by Tuesday AM at Main Lodge, up to 20” up top
Tue 11/26 – Moderate to heavy snowfall during the morning and afternoon decreases in the evening before ending overnight. Accumulations 12 – 15” by Wednesday AM at Main Lodge, up to 18” up top
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) this afternoon shows a frontal system with an embedded atmospheric river (AR) situated over Bay Area and stretching eastward into the Northern Sierra. Heavy precipitation is occurring with the AR and the warm air ahead of it has pushed snow levels in the Sierra to above 8000 feet.
The upper-level low off the California coast will push the frontal boundary southward overnight, with a weakening AR moving into the Sierra as the upper-level trough traverses eastward into central CA (image below) backed by a strong jet stream.
Heavy base-type snowfall will start after midnight, with snow levels starting out around 8500 feet. They will lower to around 7000 feet by the afternoon as dynamic cooling occurs from strong vertical motions due to upper-level divergence associated with the trough.
The snowfall should continue into the evening before tapering off and ending overnight. Model QPF (quantitative precipitation forecast) is around 1.75” for the ECM (image below) and 2.50” for the GFS (two images below). The forecast leans toward the wetter amounts due to the AR and good jet dynamics, but snow ratios will be lower than normal, around 6-8” snow to 1” liquid water.
Sunday is forecast to be mostly dry after some morning flurries, then the next storm move into central CA on later Monday as the models are suggesting a weak to moderate subtropical jet stream breakthrough aimed at the Southern Sierra (image below-purple arrow). That means more base-type snowfall is likely Monday afternoon and a times through Tuesday.
The ECM model is the wetter model this time around with almost 3” liquid (image below) with the GFS showing about 2” (two images below). Snow levels may start around 6000 feet Monday and then should hover around 7-7500 Tuesday and snow ratios again will be low as this will not be dry powder.
The models ‘ total precipitation for the event is generally in the 4-5” range (images below), which will likely result in about 2-3 feet of snowfall at Main and four-plus feet up top.
Mother Nature is coming through for us this year with a lot of base-type snowfall to start the season. Coverage for Thanksgiving this year should be great. For those hitting the early season powder, don’t forget it is still low tide out there with lots of hidden rocks and gems.
Long Range (Days 5+):
The longer-range guidance favors dry weather returning for the latter part of next week and through early December. The next snowfall might not occur until the second week of December or later, as there are no clear signs of the next storm cycle.
The ECM (image below) develops a strong ridge over the PacNW and a low over Baja, which is a classic Rex-blocking pattern with a deep trough in the East for the last part of November and early December.
The GFS is similar with just less amplitude with the ridge (two images below). These patterns are often hard to break and can last longer than what the models predict. The latest guidance is that this pattern will last into the second week of December for an extended stretch of dry weather.
The fantasy range forecast for December by the ECM favors a dry month (image below), although that model also predicted November to be dry. The Canadian model (image below) has average precipitation for December (two images below), while the CFS is the only wetter model (three images below). That doesn’t lend much confidence when all the models say something different.
The change in the pattern during December may end up being related to the track and strength of the Madden Julian Oscillation (MJO) that has been quite active this fall, having circumnavigated the globe twice over the past three months and is responsible for the current AR event in NorCal.
The MJO (image below of CFS forecast) will be moving into the dry phases 4 and 5 during the last part of November and early December, and depending on how fast eastward it moves into eastern phases 6 and 7, it may determine when precipitation returns to CA.
My guess is it will happen over the latter half of December, with the first half mostly dry. WG
