New snow is falling this morning and will increase in intensity by mid morning. There is not enough new snow yet to issue an avalanche danger rating but I am confident the avalanche danger will quickly rise to Considerable this afternoon as snow accumulates over 12-16 inches. Strong southwest winds will form sensitive wind slabs. By this evening, there could be 18 to 24” of new snow at the higher elevations.
Snow began falling in the Leavitt Lake area yesterday –this morning there is 10 inches of snow at Leavitt Lake. Snowfall is picking up over the forecast area with 4 inches of snow recorded on the Mammoth Pass snow pillow and two inches of new snow at the June Mountain weather plot. The storm is just now reaching the area and heavy snowfall is expected later this morning.
As new snow accumulates later today, the primary avalanche concern is storm slab avalanches. Winds are from the west southwest this morning but be aware that northeast winds are blowing on the north facing slopes at the top of Mammoth.
Storm slabs are soft cohesive layers of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems will last through Friday. Storm slabs are most dangerous on slopes with terrain traps – gullies, couloirs, over cliffs or other terrain features that make it difficult for a rider to escape off the side. The most sensible way to reduce your exposure to avalanche risk is waiting a day or two after a storm before venturing into steep terrain. Of course most people do not wait so it’s up to you to be alert for nature’s warning signs- cracking, whumpfing, wind loaded slopes, recent avalanches and on going wind loading.
The second avalanche problem is the weak, lousy snow structure that will get stressed today as the storm intensifies. I do not know if there will be widespread instability within this old layer but avalanches triggered on the old weak snow could be large. Areas to watch out for are thin rocky areas adjacent to thick denser wind loaded snow and where shaded sub alpine slopes roll over abruptly- the places where it’s easy to get some air. If you are traveling on flat ground in meadows and whumpfing occurs, treat slopes above you with great caution.
|0600 temperature:||32 deg. F.|
|Max. temperature in the last 24 hours:||50 deg. F.|
|Average wind direction during the last 24 hours:||SW|
|Average wind speed during the last 24 hours:||15 mph|
|Maximum wind gust in the last 24 hours:||45 mph|
|New snowfall in the last 24 hours:||3 inches|
|Total snow depth:||16 inches|
The winter storm is moving south from the Reno area this morning. Heavy snowfall is expected this morning, continuing into the afternoon. Another round of snow is possible tonight. A Winter Weather Advisory is in effect until 4AM Friday morning. 6 to 10 inches of snow is expected to fall at the 8,000 to 10,000 ft elevations today with another 4 inches tonight. 8 to 12 inches is expected to fall above 10,000 ft.
Temperatures today will be 20 degrees colder than yesterday’s balmy 50’s. Highs over the next few days will be ion the upper 20’s to low 30’s.