SIERRA NEVADA — An Omega block weather pattern is forming across the lower 48 U.S. states, with a large area of high pressure pushing the jet stream north. As the pattern develops, two areas of low pressure are expected to form—one over the Northeast and another over the West Coast—bringing cooler weather to both regions.
The western edge of the Omega block is expected to take shape on Wednesday and Thursday, according to the FOX Forecast Center. Cooler air moving into the West Coast will trigger snow development in the higher terrain of the Sierra Nevada. A round of rain and snow is forecast to arrive in the Sierra Nevada during the day on Wednesday and taper off by Thursday morning, followed by another round of mountain snow Thursday night.
At least 8 to 12 inches of snow are possible in the Sierra Nevada, with some higher elevations potentially receiving 12 to 18 inches, according to the FOX Forecast Center. Higher elevations in Alpine County are at risk of heavy snowfall, though the main Lake Tahoe area is expected to experience minimal impacts. Mammoth Lakes, California, could receive 3 to 5 inches of snow through Thursday.
"One oddity with this setup is that the main flow is coming from the north as low pressure sits over Nevada and the Rockies," the FOX Forecast Center said. "Typically, snow across this region occurs when atmospheric rivers move down the West Coast, with winds out of the southwest pulling in Pacific moisture," the center said.
Persistent strong winds are also expected across much of the Southwest, with wind advisories in place through Thursday for parts of Nevada and California. The latest snow on record for Mammoth Lakes, California, occurred on June 16, 1995.