The "Coldest Storm of the Season" continues in San Diego through Saturday.
NBC San Diego says there could be more than a foot of snow in the mountains, with temperatures 10 to 15 degrees below average for this time of year at the coast and 15 to 25 degrees below normal in the valleys and deserts.
Many parts of San Diego County could see three inches of rain with the potential to cause flooding.
The weather service issued its first-ever blizzard warning for the mountains of San Bernardino County from early Friday until Saturday afternoon. Back in 1989 the NWS issued a statement that warned of "blizzard conditions" with that particular extreme weather system. Although it was not called the same thing, it meant the same thing as today's blizzard warning.
On Thursday, the first signs of snow on the ground were in between Ramona and Santa Ysabel — elevation there is around 2,800 feet.
Then, another storm system in the form of an atmospheric river will take aim at San Diego County -- and that's when the downpours begin. The heaviest rain is expected Friday and Saturday.
Atmospheric rivers are plumes of moisture in the sky over the ocean. Once storms draw moisture from the rivers in the sky, they're capable of producing long periods of significant precipitation. The weather phenomenon is behind some of the wettest winters on record in California.
More warnings here.