A rather intense, cold, wet trough will move through California Friday into Saturday morning. This is likely to bring some rain to many parts of the state and even snow to the Sierra. The greatest amount of rain is likely to be in the north-central to central part of the state with between 0.30 and 0.60 of an inch falling with locally higher amounts. The locally higher amounts are especially likely in the west-facing mountain slopes and also due to scattered thunderstorms occurring as well. If any particular place gets a thunderstorm, they can get not only heavy downpours but also strong winds and hail. The snow level in the Sierra drops to 4,000 to 4,500 feet with 5 to 10 inches of snow likely above 5,500 feet.
In Southern California, much of the rain will fall Friday evening and night, with a shower or two lingering into Saturday morning in the mountains, across San Diego County, and maybe the eastern deserts as well. Rainfall amounts in the south will be less than farther north. However, this gets a little tricky as models have been waffling back and forth all week with this. It is my opinion that rain amounts will average 0.10 to 0.30 of an inch, and there could be a thunderstorm in a few spots as well. There even can be a little snow in the Southern California mountains in places like Mountain High and around Big Bear.
An offshoot of this storm will be wind. Strong winds precede then follow the frontal passage in all the mountains and across all the deserts. Winds of 20 to 40 mph in the deserts Friday night and Saturday will cause local blowing sand and dust. Gusty northwest winds are also likely for a time in the San Joaquin Valley and along the Central Coast.
Temperatures will drop to well below normal Friday and Saturday from north to south.
Big changes will occur next week. A strong ridge of high pressure will rapidly develop causing a huge rise in temperatures. By Tuesday and Wednesday, much of Southern California away from the water will be in the 90s, and we could see a few isolated 100-degree temperatures. The Central Valley also heats up with middle to upper 80s in the central and southern Sacramento Valley and into the lower 90s in the San Joaquin Valley. With offshore pressure gradients even the coastal plain of the Central Coast gets much warmer with at least 80s, perhaps a few 90s interior coastal valleys.
As of the end of June there had been no named storms in the Eastern Pacific basin.
This is some serious and dangerous heat. Outdoor activity is just not at all recommended during the daytime.
A strong ridge of high pressure in the West brings the highest heat of the season so far to a large area.
Combine the cold with the wind and some precipitation and there is a real danger of hypothermia.
Any shower and thunderstorm can contain heavy downpours, heavy enough to cause temporary, low-lying ponding.
According to all long-range models, the warmest area in North America compared to average will be over the Northwest.