A storm west of the border of northern California and Oregon will bring more spring rain and thunderstorms with mountain snow into Wednesday.
The satellite picture from mid-afternoon Monday shows the storm out at 130 west. A cold front ahead of that upper-level feature was moving through northern California.
I will deal with this storm in two parts. How it will impact northern and central California and the impact on Southern California.
Northern and Central California:
A period of steady rain and a thunderstorm with the cold front will end from northwest to southeast through the first half of the night. Some of that rain has been heavy and a few thunderstorms have occurred as well and that will continue to be the case into early tonight. The rain will come down hard enough to produce local flooding. While there can be a shower or two late tonight, there will be a relative lull for a time between the front and the upper-level feature. That lull will be more noticeably south and east of San Francisco than north. Tuesday into Tuesday evening, more showers and a few thunderstorms are likely. Any shower will contain heavy downpours, and thunderstorms could be locally severe producing damaging wind gusts, hail and even an isolated tornado. Showers will taper off late Tuesday night with Wednesday being dry in northern California and only a leftover shower in spots from the Central Coast to the San Joaquin Valley. Total rainfall averages of 1.25 to 2.25 inches are expected from the Bay Area to Sacramento Valley on north with the highest amounts in the foothills of the mountains. From the Central Coast to the San Joaquin Valley, I expect on average 0.50 to 1.00 inch.
As for snow, snow levels fall reaching 3,500 to 4,000 feet Monday night and remaining that low Tuesday and Tuesday night. Snow totals above 5,000 feet will be 8 to 15 inches with local amounts to 2 feet. Travel over the passes will be very difficult and can be halted at times. Chains will be a must.
The impact in Southern California with both the cold front and upper-level low will be noticeably less. The cold front will arrive late Monday night and move out Tuesday morning. It will rain but rain duration and amounts will be considerably less than in the north. Around the Los Angeles Basin, look for two to three hours worth of rain with amounts averaging 0.05 to 0.15 of an inch with up to 0.40 of an inch in the mountains of Ventura and Los Angeles County. The least rain will fall in Orange County, parts of the I.E. and San Diego County. Snow levels will average 5,000 to 5,500 feet with a couple of inches of snow above 6,000 feet. There will be a sizable break in precipitation events between the passage of the cold front and the arrival of the upper-level feature precipitation. The clouds are likely to break for some sun, and most of the rest of Tuesday will be rain-free. Showers will redevelop late in the day into Tuesday night, and there can be a thunderstorm in spots as well. Even at this time, the impact of the storm will be more muted than to the north. Additional rainfall amounts will be between 0.25 and 0.50 of an inch with spots that get heavier showers or a thunderstorm getting somewhat higher amounts. Snow levels will fall some more and average 4,000 to 4,500 feet with 3 to 8 inches likely above 5,000 feet. There will be snow fall over the passes, I-5, Highway 14 and I-15.
Showers will taper off some late Tuesday night, but a leftover shower or two can be around Wednesday, especially in the morning in western L.A. County and Ventura County while occurring anytime in the I.E. and San Diego County.
In the south, this will not be the blockbuster storm that I have heard some media people hype up. It’s more of a normal early spring storm. Yes, traffic will be impacted but when isn't it when rain falls of any magnitude? Snow levels will be rather low, but accumulations on main roads this late in the season is tougher than in mid-winter. This winter has had much fewer storms to deal with but, when you compare this storm to other storms in late March, it is nothing out of the ordinary.
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Dangerous heat will build across the Southwest through the middle of next week putting some records in jeopardy.
Parts of the West will bake in the heat over the next few days but cooler weather will arrive by the start of the weekend.
Models have been consistent on bringing a rigorous system from the Northwest to the Southwest this weekend.
The pattern next week will favor unsettled and cool weather for the Northwest.
Rain and mountain snow will highlight just about every day this week in the Northwest.