Powder Forecast – Friday, April 17th, 2026
Ted Schlaepfer CCM —- Mammoth Mountain WeatherGuy
Snowfall forecasts are valid at the Sesame snow course (Main Lodge) for the prior 24 hours as reported in the 6-7 AM morning snow report.
**Snowfall forecast confidence ranges from very low (1) to very high (5)
Sat 4/18 = 0”
Sun 4/19 = 0”
Mon 4/20 = 0”
Tue 4/21 = 0 – 1”
Wed 4/22 = 8 – 12“
Thu 4/23 = 2 – 4”
Fri 4/24 = 0 – 1”
Sat – Mon 4/25 – 4/27 = 2 – 4”
April Snowfall = 32”
April Forecast = 45 – 55”
Detailed 4-day Snowfall Forecast:
Sat 4/18 through Mon 4/20 – No snowfall expected all days.
Tue 4/21 – Chance for snowfall to develop during the morning, more likely during the afternoon and overnight hours. Accumulations 8 – 12“ at Main by Wednesday AM, 12”+ up top
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) from this afternoon shows an area of high pressure building into the state, with a few high clouds now drifting into NorCal. High pressure will continue to build over CA through the weekend, bringing fair, warmer weather with spring conditions on most of the mountain, except for the very top NE-facing runs.
High pressure will hold into early next week before an upper-level low-pressure system currently seen well off the Pacific Northwest coast on the satellite above drops southward off the California coast while deepening into Tuesday (image below). All the models show this upper-level low, although the exact placement, strength, and eastward movement vary across the guidance.
Clouds and wind should increase on Tuesday, with a chance of snow in the morning, but it is more likely to occur in the late afternoon or even overnight, as slower eastward movement is often the best forecast for closed lows cut off from the jet stream.
Long Range (Days 5+):
The longer-range guidance still looks pretty good for late April and seems more representative of a late-winter or early-spring pattern. Having had late-spring conditions in mid-March, it only makes sense that we are now seeing a late-winter pattern, as the law of averages plays out. Regardless, winter and snowfall return next week with winter conditions now possible on the mountain through the following weekend.
The upper-level trough is forecast by the guidance to move inland by Wednesday. The latest ECM model shows the heaviest snowfall on Tuesday evening and overnight, with Wednesday as a powder/storm day. The GFS is now in good agreement with the ECM on the timing, and both models end the snowfall on Wednesday overnight, although some ensembles have snowfall continuing through Thursday morning.
The GFS is the wettest model at just over 2” liquid (image below), and the ECM is showing only slightly less at about 1.75” (two images below). The odd model out is the Canadian mode, which only has about 0.65” for the event (three images below).
That amount is actually in line with the GFS ensemble (image below), so there is a chance that snowfall amounts could come in lower. It is still about five days out, so the forecast follows a blend of the ECM EPS (image below) at about 1.25” and the ECM deterministic run above. Best forecast right now is about a solid foot at Main and 15”+ up top, most of it falling Tuesday overnight.
The guidance favors another weaker upper-level low moving southward into CA next Friday (image below) and lingering through the weekend. The main effect will be to keep temperatures seasonably cold and winterlike on most of the mountain. It will also likely produce some snow showers at times, which could add up to a couple of inches. Conditions should be amazing for late April.
The 11-15 day forecast from the ECM EPS shows a split jet stream flow into the West Coast (image below) by the middle of the following week. That solution supports high pressure in the PacNW and possibly an under-cutting low-pressure system into CA, as suggested by the 12z ECM deterministic run (two images below).
That solution could keep temperatures seasonably cool, and there could also be a chance of light snowfall; the ECM EPS is showing almost half an inch of ice for the period (image below). The fantasy range guidance indicates this split flow pattern could continue through early May, and the ECM EPS now shows average precipitation for the first week of May. However, that is only about 0.40” of liquid, still enough for low-end powder conditions. So maybe next week won’t be the last call of the season. WG
