Powder Forecast — Friday May 5th, 2017
Ted Schlaepfer CCM —- Mammoth Mountain WeatherGuy
Dry weather ends by Saturday afternoon with increasing snow showers Saturday evening and overnight into Sunday. Snow showers or flurries are possible at times Sunday and into early Monday before ending or turning to rain showers Monday PM. Dry weather is then expected Tuesday and through the middle part of next week before there is a chance for light snow over the following weekend. Longer range models now keep a chance for light snow at times through the third week of May under seasonably cool temperatures.
Next update Friday 5/12
Snowfall forecast are for the Sesame snow course (Main Lodge)
**Snowfall forecast confidence ranges from very low (1) to very high (5)
Sat 5/6 = 0”
Sun 5/7 = 3 – 5” (H2O = 0.35” – 0.50”)**3
Mon 5/8 = ~1”
Tue 5/9 = 0”
Wed 5/10 = 0”
Thu 5/11 = 0”
Fri 5/12 = 0”
Sat – Mon 5/13 – 5/15 = 0 – 6”
May Snowfall = 0”
May Forecast = 5 – 15”
Seasonal Snowfall = 619”
Seasonal Forecast = 620 – 630”
Detailed 5-day Snowfall Forecast:
Sat 5/6 — Snow showers are possible by the afternoon hours and likely overnight and into Sunday morning. Accumulations 3 – 5” by Sunday AM
Sun 5/7 — Snow showers or flurries should continue through the morning hours before tapering off PM and becoming scattered overnight. Accumulations up to 1” by Monday AM
Mon 5/8 — Snow flurries are possible during the morning before any precipitation turns to rain PM. No accumulation expected.
Tue 5/9 — No snowfall expected.
Satellite imagery (below) shows an upper level area of low pressure of the CA/OR coast splitting off from the main low pressure system in the PacNW. The system is rather weak right now and moisture starved with only light showers on the N. Coast.
It is forecast by the numerical guidance to cut-off from the main jet while moving southward along the CA coast by Sunday AM (image below). It will pull in moisture in moisture from the northeast (Idaho) in the developing wrap-around flow as it cuts-off Saturday afternoon and overnight into Sunday for a period of mostly light snowfall with snow levels around 9K Saturday PM, falling to 7.5K overnight.
Numerical guidance says most of the precipitation will stay to the east over the White Mountains and southward into the deserts as the low will stall too far south by Monday (image below) for significant snowfall in Mammoth. However, enough moisture will move westward over the Sierra crest to give Mammoth a solid few inches of snowfall with a chance for up to 6” at the Main Lodge. Mostly dust on crust, but I bet there will be some fun turns somewhere on Sunday morning close to powder conditions.
That low finally moves eastward on Tuesday with the wrap-around flow producing light snow showers or flurries at times on Monday and then rain showers Tuesday as snow levels rise to near 10K or higher. High pressure returns Wednesday and into late next week for fair and warmer weather back to spring.
All the models then develop a trough of low pressure along the West Coast by the end of next week as high latitude blocking develops over the higher latitudes and pushes the jet farther southward than where climatology says it should be this time of year.
The ECM model (image below) moves the trough through NorCal Friday and Saturday next week while the GFS is slower by a day. The Canadian is similar to the ECM, but weaker. Currently, all the operational models keep the trough too far north for snowfall in Mammoth other than flurries with the main result being seasonably cold temps and breezy/gusty west winds.
However, it is still a week or more out and things could change with the ECM ensemble mean showing some more favorable solutions of the low digging farther southward. Regardless, it looks like cooler temperatures that weekend which could last into the following week.
The GFS operational (image below) model keeps a weak trough along the interior West with low pressure systems dropping southward around a high parked well off the CA coast. While it is only showing wind and cooler temps now, it is too far out to say there is not a chance for some snowfall.
This solution of a cool trough along the West is favored by the CFS model (and ECM model) over that week as well (image below). So there probably will be a period of cooler than normal temps that will slow the melt and daytime softening with a chance that it may stay cold enough up top to remain firm all day. There is also a chance for a storm over that period, we will have to wait and see.
The CFS model keeps a weak trough along the West Coast over the following week as well, but not nearly as deep, just cool and dry. The ECM model is showing something similar. So the trend for first part of the second half of the month is cool and breezy. We will have to wait to see if there is a surprise powder day too. WG