Powder Forecast –Friday March 5th, 2021
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 3/6 = 0”
Sun 3/7 = 0”
Mon 3/8 = 0”
Tue 3/9 = 2 – 3”
Wed 3/10 = 4 – 6”
Thu 3/11 = 2 – 3”
Fri 3/12 = 2 – 4”
Sat – Mon 3/13 – 3/15 = 0 – 6”
March Snowfall = 0”
March Forecast = 25 – 40”
Detailed 4-day Snowfall Forecast:
Sat 3/6 and Sun 3/7 – No snowfall expected both days
Mon 3/8 –Light snowfall should develop during the afternoon and evening, tapering off overnight. Accumulations 2 – 3” by Tuesday AM, ~4” up top
Tue 3/9 – It may be dry during the day, then light/moderate snowfall develops overnight. Accumulations 4 – 6” by Wednesday AM, 6”+ up top
Short/Mid Term (Days 1 – 6):
The infrared satellite image (below) this afternoon shows a weather system moving onto the West Coast with a wave developing along the southern portions of the cold front off the central CA coast. That wave will lift the front northeastward overnight and early tomorrow as it moves through CA and will miss Mammoth. The precipitation will stay north of Yosemite and only gusty winds are expected tomorrow morning to mess up Early Ups.
High pressure will then briefly build into Mammoth tomorrow afternoon and through Sunday for fair/dry weather. Breezy southwest winds Sunday may lead to some wind buff conditions in the upper part of the mountain.
The numerical guidance is then saying an fairly deep and cold upper-level low pressure system will develop along the CA coast Monday (image below) and then move southward through mid-week (two images below). Unfortunately, it appears now the system will not be tapping into a good moisture source and that will limit the snowfall production.
The initial front will move down the Sierra Monday afternoon and night for a period of light snowfall before the upper level system edges closer to the coast Tuesday night and into Wednesday. That could result in a period of heavier snowfall, although most of the liquid precipitation will stay on the west side of the Sierra by that point as the best orographic effects from the jet stream will have already moved south of Mammoth by early Wednesday.
The latest ECM stalls the movement eastward of the upper-low and keeps it over central/southern CA through Thursday (image below). The Canadian is similar while the GFS is more progressive with the low southeastward. If the ECM/Canadian solutions are correct, then there could be some wrap-around easterly up-slope snowfall Thursday night and Friday that could result in more snowfall. The Canadian model actually has most of the snowfall for Mammoth occurring then.
While the models have backed off with the liquid amounts, the good news is that the system is cold and what snow does fall will be the cold, dry, fluffy type of powder. Liquid to snow ratios will probably be in the 12-15”:1” range, especially by Wednesday morning when the coldest air arrives.
GFS ensemble averages (image below) are generally showing about an inch or slightly less of liquid with the Canadian showing slightly more (two images below) than the GFS operational model (three images below) due to the wrap-around snowfall. So the snowfall may add up to a foot over a few days with the best chance for powder conditions on Wednesday morning. Conditions should be good by mid-week.
Long Range (Days 6+):
The longer-range guidance is showing additional chances for powder days through mid-month, but is certainly not bullish on anything significant.
After the system departs by the end of the week, the models are saying another one may move into CA around Sunday per the GFS ensemble (image below) or later Monday/Tuesday per the latest ECM run (two images below). The Canadian model is completely different and has a very deep/cold trough over CA adding to the uncertainty.
The GFS ensemble then redevelops the long-wave trough along the West Coast by the middle part of the following week (image below) and doesn’t move it eastward until the following weekend (two images below). That will mean additional storm chances of varying intensity, hoping far enough southward for Mammoth.
The details for that week are highly questionable, but a big storm pattern is not looking probable at this time. Overall, the GFS ensemble mean is showing about 2” liquid for the entire period (image below) with about an inch or so over the back end of the forecast. Nothing too big, but certainly there could be a storm or two that produce enough for low-end powder conditions. WG