Powder Forecast — Friday May 12th, 2017
Ted Schlaepfer CCM —- Mammoth Mountain WeatherGuy
Mostly cloudy today with a chance for light snow or flurries through this afternoon and into this evening above 8500 feet before any snow showers end tonight. Dry weather returns tomorrow followed by another chance for light snow showers Sunday. Powder conditions are not expected through this weekend and into Monday next week. A stronger storm is possible Tuesday next week for a chance for powder conditions with dry and warmer weather returning by the end of next week and following weekend back to spring conditions. Generally seasonably weather with just a slight chance for an infrequent storm is then expected through early June.
Next update Friday 5/19
Snowfall forecast are for the Sesame snow course (Main Lodge)
**Snowfall forecast confidence ranges from very low (1) to very high (5)
Amounts Update Monday 5/15 @ 1PM
Tue 5/16 = 2 – 4” (H2O = 0.30” – 0.50”)**4
Wed 5/17 = 2 – 3” (H2O = 0.20” – 0.30”)**3
Thu 5/18 = 0”
Fri 5/19 = 0”
Sat – Mon 5/20 – 5/22 = 0”
May Snowfall = 5.5”
May Forecast = 10 – 15”
Seasonal Snowfall = 624.5”
Seasonal Forecast = 630 – 640”
Detailed 5-day Snowfall Forecast:
Sat 5/13 — No snowfall expected.
Sun 5/14 — Snow showers or flurries are possible by the afternoon/evening hours, ending overnight. Accumulations up to 1” by Monday AM
Mon 5/15 — Snow flurries are possible during the afternoon/evening. No accumulation expected.
Tue 5/16 — Snow probably develops during the morning hours and continues into Tuesday night, probably ending Wednesday AM. Accumulations up to 5 – 10” by Wednesday AM
Satellite imagery (below) shows the southern end of a weak cold front being currently dragged through the central Sierra with the front moving into Mammoth this afternoon. It is cloudy and foggy mid-mountain upward this afternoon and that should give way to light snow or flurries this afternoon and evening, ending overnight. Not expecting any meaningful accumulation.
Mammoth is in between systems Saturday for sunny and seasonably cool temperatures before a weak trough (image below) slides southward into CenCal on Sunday. That will lower temperatures some more on the mountain (conditions could stay firm all day up top) and also produce a chance for light snow during the afternoon and evening hours. Not expecting any meaningful accumulation.
Snow showers or flurries are also possible again Monday under continued seasonably cold temperatures before a stronger storm is possible around Tuesday next week which could be a May surprise. The ECM model (image below) is now is better agreement with the GFS model (two images below) about the trajectory and strength of an upper level low pressure system moving southward from the Gulf of Alaska.
The low isn’t taking a great trajectory down the coast to inject a lot of needed moisture, but it does appear quite dynamic for this time of year and also rather cold with snow levels possibly getting down to near 4K on the back end of the storm. Models say snow may start Tuesday morning and continue overnight and into early Wednesday.
The GFS model backed off a bit on the amounts for the storm on the 12Z run (image below), now showing about half an inch after depicting around an inch in earlier runs. The ECM model was drier than the GFS over the last couple of days, but now shows almost 0.75” liquid. However, the latest run of the Canadian has the low as an insider slider and no significant snowfall for Mammoth.
Still a bit early for an accurate forecast with the current forecast a blend of guidance and recent model runs. A slightly westward track than currently projected by the models and Mammoth could see over a foot, but right now best guess is around 6” or so. I will update the forecast numbers on Monday if the current forecast of 5-10” is bunk or still valid.
The numerical guidance moves the upper low eastward by Thursday next week with high pressure building into CA in its wake for a pattern change back to more seasonable weather. The ECM model moves the ridge into CA on Friday (image below) and holds it over CA through the weekend for fair and warmer weather back to spring conditions.
The GFS ensemble mean is then forecasting more seasonable weather for the following week. It moves the jet back northward (image below) with weak high pressure remaining over CA through the almost of the end of the month.
That model does move the trough closer to the coast heading into the last parts of May which would probably result in just cooler weather and maybe wind as any storm will probably remain well north of Mammoth, although you can’t rule out an stray storm moving southward at any point, but probably not enough for powder conditions again. Next Tuesday might be it.
The CFS model (image below) does keep the longwave trough along the West Coast into early June and that would probably mean no big heat waves and not necessarily storms. June powder days are extremely rare as snow levels are usually just too high by that time of year if any storm does indeed drop southward into CA. WG