Powder Forecast — Friday April 14th, 2017
Ted Schlaepfer CCM —- Mammoth Mountain WeatherGuy
Dry and warmer weather Saturday followed by increasing clouds Sunday and light snow by the afternoon and evening. More snow, possibly heavier, is then possible by Monday night and next Tuesday with one more round of light snow showers possible Thursday before fair and warmer weather returns for Canyon Closing weekend. Generally seasonable weather with just a slight chance for an infrequent spring storm is then expected through early May or longer with spring conditions on the mountain.
Next update Tuesday 4/18
Snowfall forecast are for the Sesame snow course (Main Lodge)
**Snowfall forecast confidence ranges from very low (1) to very high (5)
Sat 4/15 = 0”
Sun 4/16 = 0”
Mon 4/17 = 1 – 2” (H20 = 0.10” – 0.20”) **3
Tue 4/18 = 3 – 5” (H20 = 0.35” – 0.50”) **2
Wed 4/19 = 3 – 5” (H20 = 0.35” – 0.50”) **2
Thu 4/20 = 0 – 2” **2
Fri 4/21 = 0 – 2” **2
Sat – Mon 4/22 – 24 = 0”
April Snowfall = ~52”
April Forecast = 60 – 65”
Seasonal Snowfall = ~610”
Seasonal Forecast = 625 – 635”
Detailed 5-day Snowfall Forecast:
Sat 4/15 — No snowfall expected.
Sun 4/16 — Dry during the morning, then light snowfall develops afternoon and evening hours, ending overnight. Accumulations 1 – 2” by Monday AM.
Mon 4/17 — Snowfall possibly develops again by Monday night and into Tuesday. Accumulations 3 – 5” by Tuesday AM with up to 6” up top.
Tue 4/18 — Snowfall may continue during the day before ending Tuesday night. Accumulations 3 – 5” by Wednesday AM with up to 6” up top.
Satellite imagery (below) shows clear skies over CA as the weather system that produced the snow yesterday has moved well eastward with weak high pressure off the coast now edging into the state. That ridge will produce dry weather Saturday with warmer temps with freezing levels getting near 10K by the afternoon. Expect spring conditions on the mountain by the afternoon except the top.
Models are then showing a weak upper level low pressure system moving into CA on Sunday (image below) with the bulk of the moisture moving into NorCal. You can see that upper level low on the satellite pic above in the central Pacific about to combine with another weak subtropical low. So the system will have moisture, but not a lot to squeeze it out. It looks like a couple inches Sunday afternoon and evening with snow tapering off overnight and probably not powder conditions on the hill Monday AM.
The numerical guidance has now come into better agreement about the rest of next week. Models develop a rather deep upper level low pressure trough in the Eastern Pacific early next week with a decent subtropical tap. However, models differ about the strength of the moisture laden short wave trough will make it to the coast around Tuesday next week.
The Canadian model (image below) is the strongest and wettest with the low pressure system and the GFS is second in line while the operational ECM model is the weakest. That model splits the trough upon landfall with the system basically falling apart as it moves through CA.
The other models are thus showing a lot more precipitation. The GFS model has over an inch of QPF (image below) which is lower than previous runs that have consistently had between 1.5-2.0” of liquid. Those amounts are what the Canadian model shows for Monday night and Tuesday that would result in well over a foot of snow.
The ECM model is usually the best model within the five day window and it has around half an inch of liquid for just a few inches of snowfall. So it is disconcerting that the model is dryer, however, the ECM mean is showing about 0.75” for Tuesday and a quarter inch Monday night for about an inch of QPF total of wet type snowfall (snow levels around 7.5-8K). That is what the current forecast is following with generally low confidence due to the large model spread.
The longer range guidance is then showing the upper level trough finally moving inland in a much weakened state around Wednesday night or Thursday next week. The ECM model (image below) splits the jet upon arrival to the coast with a short wave taking a northwest trajectory into CA around Thursday next week.
The GFS and Canadian models are a bit farther east with this feature and have it more like an inside slider type storm. Those models are mostly dry while the ECM has a few inches of snowfall late Wednesday or early Thursday. It is doubtful right now that enough snow will fall for powder conditions with a more likely scenario an increase in northwest winds and wind buff.
Models are then showing a high pressure ridge building into CA end of next week and into Canyon Closing day (image below). That means a general end to the snowfall chances with a return of dry and warm weather resulting in spring conditions for the entire mountain. Looks like nice weather now for the pond skim.
That is what the longer range GFS ensemble mean favors through the following week. It shows (image below) a continued strong jet stream moving across the north Pacific, but splitting upon hitting the West Coast with the main jet generally well north of Mammoth into the Pacific Northwest.
That model is showing the same general pattern continuing through the end of the month (image below). That means normal spring weather should return to the eastern Sierra for the last part of April with an occasional storm moving north of CA resulting in minor cool-offs and increases in winds.
The climate models show this pattern continuing through mid-May with the CFS model (image below) showing below normal precipitation in early May. Due to the progressive nature of the weather system moving across the Pacific and into the West Coast there is always a chance for one to drop far enough southward into CA for snowfall in Mammoth, although it will probably be weak and light as any May snowfall is not guaranteed.
Overall, next week might be the last call for powder this season, although that isn’t guaranteed yet to happen either. Regardless, spring skiing in May/June will be great thanks to a very deep and record setting base up top. WG