Powder Forecast — Friday March 17th, 2017
Ted Schlaepfer CCM —- Mammoth Mountain WeatherGuy
Dry weather continues into Saturday with lots of clouds over the weekend and a chance for flurries during the late afternoon/evening on both Saturday and Sunday, but no significant snowfall. Snowfall probably develops by late Monday and Tuesday next week with another storm possible toward the end of next week and into the following weekend. Longer range climate models say colder type storms could then continue at times into mid-April with periods of dry weather as well.
Next update Tuesday 3/21
Snowfall forecast are for the Sesame snow course (Main Lodge)
**Snowfall forecast confidence ranges from very low (1) to very high (5)
Sat 3/18 = 0”
Sun 3/19 = 0”
Mon 3/20 = 0 – 1”
Tue 3/21 = 0 – 3”
Wed 3/22 = 9 – 12” (H20 = 1.00” – 1.50”)**3
Thu 3/23 = 2 – 5”
Fri 3/24 = 0 – 3”
Sat – Mon 3/25 – 27 = 15 – 24”
March Snowfall = 10.5”
March Forecast = 40 – 55”
Seasonal Snowfall = 520.5”
Seasonal Forecast = 600 – 625”
Detailed 5-day Snowfall Forecast:
Sat 3/18 and Sun 3/19 — No snowfall expected both days except for a chance for afternoon/evening flurries.
Mon 3/20 — Probably dry during the day, then snow develops late night or early Tuesday. Accumulations up to 3” by Tuesday AM.
Tue 3/21 — Snow is likely during the day and probably continues at times overnight and into Wednesday. Riders of the storm day. Accumulations up to 9 – 12” by Wednesday AM. Over a foot up top.
A high pressure ridge (image below) is centered over the southern part of the state today with an area of low pressure in the Gulf of Alaska off the British Columbia coast and associated frontal system that is connected to a weaker area of low pressure well off the CA coast. Both of those systems are slowly moving eastward.
Models say the weak low will generally fall apart when it moves ashore into NorCal tomorrow (image below) while the upper low in the G.A tracks into the PacNW.
Nonetheless, it will knock the high pressure ridge eastward Saturday for colder temps (freezing level lowers to 9K) and clouds will be drifting over Mammoth at times both Saturday and Sunday for periods of flat light. No snowfall is expected other than a chance for afternoon/evening flurries.
The models per the GFS below then moves a stronger trough of low pressure toward the coast Monday and into Mammoth by Tuesday as split jet stream flow develops along the West Coast. Since the last update, the models have fluctuated with whether the system will split apart further when it moves onto the coast and not have an organized frontal passage.
The latest GFS still has over an inch of liquid Tuesday (image below) for about a foot of snow and the 0Z run of the ECM is similar while the Canadian is much slower with the eastward movement of the low and delays snowfall by about 12-18 hours from Tuesday into Wednesday.
So there is still some uncertainty with strength and timing, but it does look likely that it will snow by the middle part of next week and powder conditions will return to the mountain. Snow levels won’t be too low and around 7K so the snow won’t be dry quality.
There might not be a trailing system for Wednesday now per the latest GFS guidance with a break in snowfall through Thursday, and unfortunately, the 12 UTC run of the ECM model suites was very late today and not available as of this writing.
However, the models are still advertising a stronger storm system for the end of next week and into the following weekend and it may contain a weak AR. The GFS brings a more cohesive upper level low pressure system to the coast next Friday (image below) with snowfall developing Thursday night. The 0Z ECM was similar and only slightly slower with the start of snowfall delayed til Friday AM. The Canadian is similar to the GFS. It is a week out so details will likely change.
All the models are suggesting at least two inches of liquid precipitation with last night’s run of the ECM showing close to 3”. So it looks like this storm has the potential to drop up to two feet at Main over a couple of days with snow levels projected to be in the 5-6K range likely resulting in normal type Mammoth quality snow (not too wet, not too dry).
Last night’s ECM brings a kicker upper low into CA late Sunday and into the following Monday for a chance for more snowfall, but the other models are not showing it with ridging instead. The GFS ensemble shows ridging which is probably the best guess right now considering no ECM ensemble today.
The 12Z GFS operational model splits a short wave southward from the jet stream (image below) just before mid-month which would represent another chance for snow. I certainly don’t believe that exact solution yet, but the models are not favoring quick ridging back over CA.
The GFS ensemble is favoring a trough over CA/interior West (image below) to start April which would allow cold storms to move into CA, which is what was favored in the last update. However, the GFS has the trough farther westward now which gives the lows a better chance for over-water trajectory to pick up need moisture to produce snowfall.
The ECM climate model is still showing some form of a trough over the interior West into mid-April. The model is generally showing average precipitation for the period. So there will be storm chances at times with lows dropping southward from the Gulf of Alaska with probably dry weather too. This type of pattern is cool, so snow melt over the first half of April may be slow. WG