Powder Forecast –Friday April 18th, 2025
Ted Schlaepfer CCM —- Mammoth Mountain WeatherGuy
Last Post of the 2024-25 season
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 4/19 = 0”
Sun 4/20 = 0”
Mon 4/21 = 0”
Tue 4/22 = 0”
Wed 4/23 = 0”
Thu 4/24 = 0”
Fri 4/25 = 0”
Sat – Mon 4/26 – 4/28 = 2 – 5”
April Snowfall = 17”
April Forecast = 20 – 25”
Detailed 4-day Snowfall Forecast:
Sat 4/19 through Tue 4/22 – No snowfall expected all days.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) this afternoon shows an area of low-pressure positioned over Utah and high pressure in the the PacNW. That weak high pressure ridge will move southeastward into CA on Saturday for fair and warmer weather back to spring.
A weak short-wave trough will then move through the PacNW and far NorCal on Sunday (image below) and the only effect on the weather in Mammoth will be typical breezy winds during the afternoon under continued spring conditions.
Continued fair weather is expected early next week with slightly cooler temperatures possible by mid-week under continued dry and spring weather. Typical westerly spring winds are expected during the afternoon each day, nothing too strong, although speeds should pick up toward mid-week.
Long Range (Days 5+):
The longer-range guidance has trended toward the ECM EPS solution from the last post with a chance for snowfall over the last weekend of the month that could be enough for low-end powder conditions. Typical spring weather should then return end of the month and through early May with no clear signs of any more spring storms.
The guidance is in general agreement that a moderately deep upper-level low will drop southward into California from the Gulf of Alaska toward the end of next week. Troughing should develop by Thursday (image below) followed by the passage of the main upper-low over the weekend (two images below).
The QPF guidance is expectedly mixed with the GFS keeping most of the precipitation north of Mammoth (image below) and the Canadian keeping it west of the crest (two images below). The latest ECM deterministic run (three images below) is only forecasting a couple tenths of an inch, but the ECM EPS has almost half an inch liquid. Forecast follows a blend of the ECM and ECM EPS with a few inches favored and maybe up to 5” of snowfall.
The models are favoring a weak long-wave trough (image below) to remain in place across the SouthWest with weak northwest flow into CA. That is a mostly fair-weather pattern with seasonable temperatures, but also a pattern that could support a short-wave to drop southward into CA. If it does happen, the guidance says it will at the end of the month or first day of May. The ECM EPS is showing light amounts (two images below) for the period, maybe enough for low-end powder if it all works out perfectly.
May is favored to see typical spring weather. While most days will be sunny and warm/mild, typical spring weather also means a chance for a surprise storm. The ECM EPS (image below) is not favoring May to see any storminess with below normal precipitation for an already normally dry month, but the control run (two images below) this morning was not as dry, so you never know. Snowman will keep you posted on any weather updates and potential snowfall moving forward as this will be the last post of the season. Have a great rest of spring and summer. WG
