High Sierra Topix

The next weather system to impact the area will dropping south outof the Gulf of Alaska Thursday and move into northern CA by Friday. Strong onshore flow with rapid h500dam height falls will bring a rapid change in temperatures on Friday as the cold front pushes through. Winds are expected to increase on Thursday night and continue on Friday.

The system is expected to be mainly dry with only a chance of showers and afternoon thunderstorms in the Sierra on Friday and Saturday. An open trough will push through the Pacific NW. This system will keep an unsettled pattern in place across the Northern California area with cool temps and a few showers in the Sierra through Tuesday.

By Thursday, the weak ridge is progged with good model consistency to already begin giving way to another approaching Pacific storm system. Northern portions of our area should see slight cooling Thursday along with increasing winds, as the system drops south from the Pac Northwest.

Models remain in good agreement as they forecast the frontal system to swing inland into the Great Basin region during the weekend. This anomalously cool and deep low pressure system forthis time of year will bring significant cooling, with temperatures dropping to around 10 degrees below normal through the weekend. The increased onshore surface pressure gradients along with the surge of cooler air and upper level jet energy will maintain gusty winds through and below mountain passes during the latter part of the week.

Moisture continues to look somewhat limited with this system but model qpf guidance does show some snow accumulations over the Sierra as snow levels drop as low as 7000 ft by Friday and near 6500 ft by Saturday. Snow accumulations of a few inches are possible. A few showers and thunderstorms will also be possible into the SJ Valley Friday and Saturday, mainly north of Fresno County.

Additional shortwave impulses will rotate around this low during the first part of next week...maintaining near to slightly below average temperatures and continued shower and thunderstorm chances over the Sierra.