Friday February 17th, 2017
Ted Schlaepfer CCM —- Mammoth Mountain WeatherGuy
Snow continues for the rest of today and tonight before tapering off tomorrow for the most part. After a brief break Sunday during the day, heavy snow returns Sunday night along with strong winds with continued heavy snow at times Presidents’ Day and into next Tuesday. One last round of drier snowfall is expected Tuesday night and Wednesday before dry weather may return for a few day. Storms may then return near the end of the month or early March with longer range models suggesting dry weather could return by end of the first week of March.
Next update Tuesday 2/21
Snowfall forecast are for the Sesame snow course (Main Lodge)
**Snowfall forecast confidence ranges from very low (1) to very high (5)
Sat 2/18 = 20 – 22” (H20 = 1.85” – 2.00”) **4
Sun 2/19= 2 – 4” (H20 = 0.25” – 0.35”) **4
Mon 2/20 = 10 – 12” (H20 = 1.00” – 1.25”) **3
Tue 2/21 = 28 – 32” (H20 = 3.00” – 3.50”) **3
Wed 2/22 = 10 – 12” (H20 = 1.00” – 1.25”) **3
Thu 2/23 = 4 – 8” (H20 = 0.35” – 0.75”) **3
Storm Total = 64 – 78” (H20 = 7.45” – 9.10”) **3
Fri 2/24 = 0”
Sat – Mon 2/25 – 27 = 0 – 12”
February Snowfall = 77.5”
February Forecast = 130 – 150”
Seasonal Snowfall = 411”
Seasonal Forecast = 575”- 625”
Detailed 5-day Snowfall Forecast:
Sat 2/18 — Snowfall tapers off during the day, ends Saturday PM/night. Accumulations 2 – 4” by Sunday AM. ~6” up top.
Sun 2/19 — Likely dry during the day, then snowfall develops overnight Sunday and become heavy by dawn. Accumulations 10 – 12” by Monday AM. 12”+ up top.
Mon 2/20 — Snow, heavy at times along with strong winds, expected during the day and overnight into Tuesday. Accumulations 28 – 32” by Tuesday AM. Close to 48”+ up top.
Tue 2/21 — Snowfall likely tapers off during the day before increasing again Tuesday night and into Wednesday. Accumulations 10 – 12” by Wednesday AM. 12”+ up top.
Satellite imagery below shows a strong area of low pressure and associated fronts moving into central and southern California with stormy conditions. Enough energy has moved eastward into the Sierra today for steady snowfall in Mammoth and that should continue through tonight and into tomorrow morning as the upper level trough slides eastward.
The main upper level low pressure system well off the coast is moving southeastward into Baja (image below) over the next 24-36 hours so the heaviest snowfall should end this afternoon as the energy from the low is displaced southward.
One good thing about have the low and related strong jet stream move south is that the winds are relatively light today resulting in less fracturing of the snow crystals and thus higher liquid to snow ratios than what would be expected from this storm that is not that cold. And of course, the lifts stayed open. Over 10” has fallen as of this writing and I can imagine great turns on 22 this afternoon. GFS is showing over 2” of liquid today and tomorrow (images below), so total amounts could be close to 2 feet.
There should be a break early Sunday and at least through the morning hours before snowfall likely returns Sunday night ahead of the main event. The models, per the ECM below, are still advertising the passage of a strong upper level low pressure system Monday and into Tuesday with will contain a weak/moderate Atmospheric River (AR). The warm front moves into the area Sunday night followed by the cold front passage Monday.
This AR is not as warm as the previous event last week and snow levels will stay near 7K or lower when the heaviest precipitation occurs Monday. Those levels will come down to near 5.5K by Tuesday morning. The snow quality will be Sierra cement, but not the super wet type, just slightly heavy. GFS model (image below) is showing around 4” liquid Monday, ECM not as much (2”+) as it has the focus of the AR farther north.
The forecast leans toward the GFS solution as that makes more sense based on the upper level pattern. Not quite sure 4” will fall, but I can easily see 3”+ for the whole day and night. Expect at least two feet of snow and possibly close to 3 feet at Main with around 4 feet up top for Tuesday AM. Not sure many lifts will be open on Presidents’ Day due to strong winds with continued snow showers Tuesday under lighter winds.
The main upper level low pressure system then moves ashore Tuesday night and next Wednesday per the GFS (image below). Snow levels will be lower with this last storm, but so will liquid amounts.
Nonetheless, the models (image below) are showing at least 1” of more snow water equivalent for at least another foot of snow. Snow levels could get down to 4000 feet by early Wednesday and the snow quality will be much drier. It looks like Wednesday could be an epic powder day with snowfall tapering off during the day along with decreasing winds.
The storm cycle ends Wednesday night/Thursday followed by at least a few days of dry weather into the following weekend. The longer range pattern is not in agreement with some models dry and others showing a chance for storms to return end of the month.
The GFS model is the dry one with high pressure ridge in the Gulf of Alaska and a trough across the interior west with short waves staying east of CA. The ECM model (image below) has a blocking ridge in the Gulf of Alaska too, but it has short waves moving southward farther westward including hints of a westerly breakthrough under the ridge.
The Canadian is the most bullish (image below). It moves the upper low around the Gulf of Alaska ridge faster and deepens it off the coast quicker along with tapping subtropical moisture. It develops strong southwest flow into the Sierra along with a strong surface low for heavy snowfall for Mammoth.
The forecast right now just calls for a chance for storminess by the end of the month and early March under low confidence. The ensembles are all over the place right now with a huge spread. Using the mean, the Canadian ensemble looks like the GFS pattern and the ECM favors weak ridging.
The longer range climate models are saying that any dry weather in early March could end by the second week of March as both the CFS and ECM are favoring normal precipitation for that week (image below). So winter could continue in March, but maybe not as intense. WG