Powder Forecast – Tuesday December 17th, 2024
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)
Wed 12/18 = 0”
Thu 12/19 = 0”
Fri 12/20 = 0”
Sat 12/21 = 0”
Sun 12/22 = 0 – 1”
Mon 12/23 = 0 – 1”
Tue 12/24= 0 – 2”
Wed – Fri 12/25 – 12/27 = 6 – 12”
December Snowfall = 20”
December Forecast = 40 – 55”
Detailed 4-day Snowfall Forecast:
Wed 12/18 – Fri 12/20 – No snowfall expected all days.
Sat 12/14 – Likely dry during the day, then a chance for snowfall late PM and overnight. Maybe an inch accumulation.
Forecast Summary:
Short Term (Days 1 – 4):
The current infrared satellite image (below) this afternoon shows a weather system moving into the far northern PacNW and a high-pressure ridge building into the state.
The weather models continue to build the ridge through Thursday (image below) for a fair and dry weather this week and seasonably mild temperatures. Temps will likely get into the 30s up top by tomorrow with not much change through Friday.
A weather system will move into NorCal on Saturday (image below) and will likely not move far enough southward for any meaningful snowfall in Mammoth. The latest model deterministic runs are dry, and the ECM EPS is only showing about a tenth of an inch (two images below). Similar to the light snowfall last night that added up to an inch, anything that fall will be dust on crust.
Long Range (Days 5+):
The longer-range guidance is saying Santa is going to bring a powder Christmas gift followed by more chances through the end of the year. However, the guidance is not yet bullish on a major snowfall event. Hopefully that will change.
The models have been very consistent about the passage of a Christmas Eve short-wave trough (image below) that will dig far enough southward for meaningful snowfall in Mammoth. We are now getting toward mid-winter when the guidance performs better in the longer time ranges.
Hopefully then then models are right about a 7-8-day QPF of over an inch with the ECM showing about 1.25” (image below) and the GFS about an inch (two images below). The ECM EPS is showing only slightly less at just under an inch (three images below). Thus, there is currently a good chance for at least 6” at Main and maybe up to a foot. That would be a nice X-mas present.
The fantasy range guidance keeps the storm track active into the West Coast with a breakthrough of the westerlies or zonal flow into NorCal and the PacNW (image below). The jet stream (purple arrow) might be too far northward for big snowfall in Mammoth at first with the GFS ensemble moving it farther southward over the last weekend of 2024 (image below) for a better chance of snowfall.
The ECM EPS is showing only enough for low-end powder conditions (image below) and not that much overall as the zonal jet may not have a great moisture tap. The CFS model (two images below) is showing more for central CA and over an inch liquid for Mammoth that would be enough for powder. If the MJO (three images below) keeps its amplitude as some models are forecasting, then the wetter solutions will probably verify.
The super long-range guidance is not favoring any storm patterns until the second week of January, primarily the CFS model (image below). That model’s forecast is consistent with the MJO moving into the favorably wet phase 3 (two images below) mid-month. The ECM model has the MJO weakening considerably in January and moving into the unit circle with no directional signal. The ECM is currently favoring slightly below normal precipitation in January. Hope that model is wrong again. WG
