Powder Forecast – Tuesday, April 30th, 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.
The next post will be on Friday, 5/3
**Snowfall forecast confidence ranges from very low (1) to very high (5)
Wed 5/1 = 0”
Thu 5/2 = 0”
Fri 5/3 = 0”
Sat 5/4 = 0”
Sun 5/5 = 9 – 15″
Mon 5/6 = 1 – 2″
Tue 5/7 = 0”
Wed – Fri 5/8 – 5/10 = 0 – 2”
April Snowfall: 31″ April Forecast = 31”
Detailed 4-day Snowfall Forecast
Wed 5/1 through Fri 5/3 – No snowfall expected all days.
Sat 5/4– Dry during the morning, then snowfall develops during the afternoon and becomes heavy at times overnight before taping off near dawn. Accumulations 9 – 15″ at Main, 15″ + up top by Sunday AM.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) today shows a low-pressure system positioned in the PacNW and another moving toward British Columbia. A dry cold front is also positioned across far NorCal and southern Oregon. High pressure is parked far off the California coast.
The weather systems in the PacNW will move southward east of CA as inside slider type systems over the next couple of days (image below). Their passage east of Mammoth won’t do much except keep high pressure from building too strongly and thus temperatures generally seasonable/spring. Dry weather should continue Friday with slightly warmer temps.
Changes in the weather pattern back to winter are expected this weekend as an unseasonably deep upper-level trough moves into the state. The exact strength and track of the upper-low is still yet to be determined, with the GFS (image below) not being as progressive as the ECM model (two images below), which moves the trough through the state quicker and farther northward. The GFS deterministic solution is well supported by its ensemble mean (three images below).
The upper low will drive a strong cold front for early May into the state early Saturday and then into the Sierra Saturday afternoon and night. The current timing is snowfall starting in Mammoth on Saturday afternoon and becoming heavy during the evening/overnight. The more progressive ECM ends snowfall by dawn Sunday, while the slower GFS continues into Sunday night. The Canadian is more similar to the ECM.
Model QPF varies, with the more progressive models showing lesser amounts versus the slower and farther southward GFS (image below), which has about 1.5″ liquid for Mammoth and 2.5″ west of the crest. The ECM model (two images below) has just under an inch, and the Canadian (three images below) has about 0.75″ liquid and an inch west of the crest. The NBM (four images below) is the driest.
The current forecast follows a blend of the ECM mean (image below) and a bit more of the GFS ensemble mean (two images below), which has been more consistent with this potential storm as the ECM model has been trending toward it. About an inch of liquid is favored, and around a foot of snowfall is favored at Main. The GFS solution would favor closer to 20″; hopefully, that will verify.
Snow levels will start out around 7K Saturday afternoon and then drop to near 5000 feet Saturday night. If the GFS is right, snow levels will remain around 5-5500 feet Sunday as light snowfall continues. An ECM solution would be a bluebird powder day. The next update will be on Friday.
Long Range (Days 5+):
The longer-range guidance suggests there will be an additional chance for light snowfall around the middle of next week and then back to the normal spring conditions.
The Canadian model is the most bullish about a stronger trough around Wednesday next week (image below), although the model suggests it will be moisture-starved and will mostly be a wind event. The ECM model’s solution (two images below) is more of a slider-type upper-level low that just keeps temperatures cool and conditions breezy. The GFS is similar to the ECM model.
Thus, there is a chance for light snowfall around Tuesday/Wednesday, but likely not enough for powder conditions. A handful of ensembles have better over-water trajectories before landfall, so there is a slight chance that solutions could become more favorable.
Longer range GFS ensemble mean forecasts (image below) suggest a more typical spring pattern heading into mid-month with a weak trough east of CA and a weak ridge just off the coast. That would result in dry weather and mostly seasonable or spring weather conditions. The last call for powder might be this weekend. WG
